Chapter 9 Lens

ACQUIRED CATARACT 270

Age-related cataract 270

Cataract in systemic diseases 272

Secondary cataract 273

Traumatic cataract 273

MANAGEMENT OF AGE-RELATED CATARACT 273

Preoperative considerations 273

Intraocular lenses 279

Anaesthesia 280

Phacoemulsification 281

Small incision manual cataract surgery 285

Operative complications 285

Acute postoperative endophthalmitis 289

Delayed-onset postoperative endophthalmitis 293

Posterior capsular opacification 295

Anterior capsular fibrosis and contraction 296

Miscellaneous postoperative complications 296

CONGENITAL CATARACT 298

Aetiology 298

Inheritance 298

Morphology 298

Systemic metabolic associations 298

Associated intrauterine infections 302

Associated chromosomal abnormalities 302

Associated skeletal syndromes 302

Management 303

ECTOPIA LENTIS 304

Without systemic associations 304

With systemic associations 304

Management 307

ABNORMALITIES OF SHAPE 308

Anterior lenticonus 308

Posterior lenticonus 308

Lentiglobus 309

Microspherophakia 309

Microphakia 309

Coloboma 309

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Acquired cataract

Age-related cataract

Subcapsular cataract

Anterior subcapsular cataract lies directly under the lens capsule and is associated with fibrous metaplasia of the lens epithelium. Posterior subcapsular opacity lies just in front of the posterior capsule and has a vacuolated, granular, or plaque-like appearance on oblique slit-lamp biomicroscopy (Fig. 9.1A) and appears black on retroillumination (Fig. 9.1B). Due to its location at the nodal point of the eye, a posterior subcapsular opacity has a more profound effect on vision than a comparable nuclear or cortical cataract. Near vision is frequently impaired more than distance vision. Patients are particularly troubled under conditions of miosis, such as produced by headlights of oncoming cars and bright sunlight.

Fig. 9.1 Age-related cataract. (A) Posterior subcapsular; (B) on retroillumination; (C) nuclear; (D) on retroillumination

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – figs A-C)

Nuclear cataract

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Nuclear cataract starts as an exaggeration of the normal ageing changes involving the lens nucleus. It is often associated with myopia due to an increase in the refractive index of the nucleus, and also with increased spherical aberration. Some elderly patients may consequently be able to read without spectacles again (’second sight of the aged’). Nuclear sclerosis is characterized in its early stages by a yellowish hue due to the deposition of urochrome pigment. This type of cataract is best assessed with oblique slit-lamp biomicroscopy (Fig. 9.1C) and not by retroillumination (Fig. 9.1D). When advanced the nucleus appears brown.

Cortical cataract

Cortical cataract may involve the anterior, posterior or equatorial cortex. The opacities start as clefts and vacuoles between lens fibres due to hydration of the cortex. Subsequent opacification results in typical cuneiform (wedge-shaped) or radial spoke-like opacities, often initially in the inferonasal quadrant (Fig. 9.2A and B). Patients with cortical opacities frequently complain of glare due to light scattering.

Fig. 9.2 Age-related cataract (A) Cortical; (B) on retroillumination; (C) Christmas tree; (D) on retroillumination

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – figs A and B)

Christmas tree cataract

Christmas tree cataract, which is uncommon, is characterized by striking polychromatic needle-like deposits in the deep cortex and nucleus (Fig. 9.2C and D); they may be solitary or associated with other opacities.

Cataract maturity

1 Immature cataract is one in which the lens is partially opaque.

2 Mature cataract is one in which the lens is completely opaque (Fig. 9.3A).

3 Hypermature cataract has a shrunken and wrinkled anterior capsule due to leakage of water out of the lens (Fig. 9.3B).

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4 Morgagnian cataract is a hypermature cataract in which liquefaction of the cortex has allowed the nucleus to sink inferiorly (Fig. 9.3C and D).

Fig. 9.3 Cataract maturity. (A) Mature cataract; (B) hypermature cataract with wrinkling of the anterior capsule; (C) Morgagnian cataract with liquefaction of the cortex and inferior sinking of the nucleus; (D) total liquefaction and absorption of the cortex with inferior sinking of the lens

(Courtesy of P Gili – fig. D)

Cataract in systemic diseases

Diabetes mellitus

Hyperglycaemia is reflected in a high level of glucose in the aqueous humour, which diffuses into the lens. Here glucose is metabolized by aldose reductase into sorbitol, which then accumulates within the lens, resulting in secondary osmotic overhydration of the lens substance. In mild degree, this may affect the refractive index of the lens with consequent fluctuation of refraction pari passu with the plasma glucose level (hyperglycaemia resulting in myopia and vice versa). Cortical fluid vacuoles develop and later evolve into frank opacities.

1 Classic diabetic cataract, which is rare, consists of snowflake cortical opacities (Fig. 9.4A) occurring in the young diabetic. Such a cataract may resolve spontaneously or mature within a few days (Fig. 9.4B).

2 Age-related cataract occurs earlier in diabetes mellitus. Nuclear opacities are common and tend to progress rapidly.

Fig. 9.4 Cataract in systemic disease. (A) Diabetic snowflake cataract; (B) advanced diabetic cataract; (C) stellate posterior subcapsular cataract in myotonic dystrophy; (D) advanced left cataract in a patient with myotonic dystrophy; (E) bilateral advanced cataracts in atopic dermatitis; (F) shield-like anterior subcapsular cataract in atopic dermatitis

(Courtesy of A Fielder – fig. A; J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. B; L Merin – fig. D)

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Myotonic dystrophy

Myotonic dystrophy is an AD condition characterized by delayed muscular relaxation after cessation of voluntary effort (myotonia – see Ch. 19). About 90% of patients develop visually innocuous, fine cortical iridescent opacities in the 3rd decade which evolve into visually disabling stellate posterior subcapsular opacities (Fig. 9.4C) by the 5th decade that may progress to maturity (Fig. 9.4D); occasionally cataract may predate myotonia.

Atopic dermatitis

About 10% of patients with severe atopic dermatitis develop cataracts in the 2nd–4th decades; these are often bilateral and may mature quickly (Fig. 9.4E). Shield-like dense anterior subcapsular plaque which wrinkles the anterior capsule is characteristic (Fig. 9.4F). Posterior subcapsular opacities resembling a complicated cataract may also occur.

Neurofibromatosis type 2

NF2 (see Ch. 19) is associated with cataract in about 60% of patients. It tends to develop prior to the age of 30 years. They may be posterior subcapsular or capsular, cortical or mixed.

Secondary cataract

A secondary (complicated) cataract develops as a result of some other primary ocular disease.

Chronic anterior uveitis

Chronic anterior uveitis is the most common cause. The incidence is related to the duration and activity of intraocular inflammation that results in prolonged breakdown of the blood–aqueous and/or blood–vitreous barrier. The use of steroids, topically and systemically, is also important. The earliest finding is a polychromatic lustre at the posterior pole of the lens which may not progress if the uveitis is arrested. If the inflammation persists, posterior (Fig. 9.5A) and anterior opacities (Fig. 9.5B and C) develop that may progress to maturity. The opacities appear to progress more rapidly in the presence of posterior synechiae.

Fig. 9.5 Secondary cataract. (A) Early uveitic posterior subcapsular cataract; (B) uveitic anterior plaque opacities; (C) extensive posterior synechiae and anterior lens opacity; (D) glaukomflecken

Acute congestive angle-closure

Acute congestive angle-closure may cause small, grey-white, anterior, subcapsular or capsular opacities within the pupillary area (glaukomflecken – Fig. 9.5D). They represent focal infarcts of the lens epithelium and are almost pathognomonic of past acute angle-closure glaucoma.

High myopia

High (pathological) myopia is associated with posterior subcapsular lens opacities and early-onset nuclear sclerosis, which may ironically increase the myopic refractive error. Simple myopia, however, is not associated with such cataract formation.

Hereditary fundus dystrophies

Hereditary fundus dystrophies, such as retinitis pigmentosa, Leber congenital amaurosis, gyrate atrophy and Stickler syndrome, may be associated with posterior subcapsular lens opacities (see Ch. 15). Cataract surgery may occasionally improve visual acuity even in the presence of severe retinal changes.

Traumatic cataract

Trauma is the most common cause of unilateral cataract in young individuals and may include the following.

1 Penetrating trauma (Fig. 9.6A).

2 Blunt trauma may cause a characteristic flower-shaped opacity (Fig. 9.6B).

3 Electric shock and lightning strike are very rare causes that may result in anterior and posterior iridescent opacities that have a stellate pattern (Fig. 9.6C).

4 Infrared radiation, if intense as in glassblowers, may rarely cause true exfoliation of the anterior lens capsule (Fig. 9.6D).

5 Ionizing radiation for ocular tumours may cause posterior subcapsular opacities (Fig. 9.7E) that may develop months or years later.

Fig. 9.6 Causes of traumatic cataract. (A) Penetrating trauma; (B) blunt trauma; (C) electric shock and lightning strike; (D) infrared radiation (glassblower’s cataract); (E) ionizing radiation

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – figs C-E)

Management of age-related cataract

Preoperative considerations

Indications for surgery

1 Visual improvement is by far the most common indication for cataract surgery. Operation is indicated only if and when the opacity develops to a degree sufficient to cause difficulty in performing essential daily activities.

2 Medical indications are those in which a cataract is adversely affecting the health of the eye, for example, phacolytic or phacomorphic glaucoma (see Ch. 10). Cataract surgery to improve the clarity of the ocular media may also be required in the context of fundal pathology (e.g. diabetic retinopathy) requiring monitoring or treatment.

Systemic preoperative assessment

For elective surgery, a general medical history is taken and any problems managed accordingly. Table 9.1 sets out suggested further enquiry and action in relation to a range of systemic diseases. Routine preoperative general medical examination, blood tests and ECG are not usually required for local anaesthesia.

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Table 9.1 Management of general medical conditions prior to elective surgery

Condition	Further questions/examination	Action
Diabetes mellitus	Well-controlled? Will need blood test (finger-prick may be sufficient, consider additional tests if necessary)	If control poor, may need to defer surgery and contact patient’s physician Medication and food and drink intake as usual on the day of surgery for local anaesthesia
Systemic hypertension	If systolic >170 or diastolic >100 may need physician opinion	Consider contacting physician for optimization; defer surgery if necessary as risk of suprachoroidal haemorrhage may be elevated
Actual or suspected myocardial infarction (MI) in the past	Date of MI?	Defer surgery for at least 6 months from date of MI. Contact physician/anaesthetist if concerns about current cardiovascular status
Angina	Stable/well-controlled?	Bring glyceryl trinitrate (GTN) spray on day of surgery. If unstable, contact physician or anaesthetist
Respiratory disease	Is chest function currently optimal? Can the patient lie flat?	If the patient cannot lie flat, may need to discuss with operating surgeon. Trial of lying flat (at least half an hour) Remind patient to bring any inhalers to hospital
Rheumatic fever, transplanted or prosthetic heart valve, previous endocarditis	Does the patient usually require prophylactic antibiotic cover for operations?	Antibiotic prophylaxis only exceptionally required for ophthalmic surgery e.g. removal of an infected eye
Stroke in the past	Date of stroke? Particular residual difficulties?	Defer surgery for at least 6 months from date of stroke. Many have positional/other practical consequences
Rheumatoid arthritis	Does the patient have any problems lying flat or with neck position?	If in doubt about patient’s ability to position appropriately, may need to discuss with operating surgeon
Jaundice in the past	What was the underlying diagnosis?	If viral hepatitis suspected, note prominently as special precautions to avoid needlestick injury may be necessary
HIV infection	If there are any high-risk factors, has the patient undergone an HIV test in the past?	Special precautions to avoid needlestick injury may be necessary
Sickle status	For patients of southern Asian and Afro-Caribbean ethnic origin, enquire about sickle status	Blood test if unknown and general anaesthesia planned
Parkinson disease or other cause of substantial tremor	Is the patient able to maintain head stability sufficiently to cooperate with local anaesthesia and surgery?	If not, may require general anaesthesia
Epilepsy	Is the condition well-controlled?	General anaesthesia may be preferred
Myotonic dystrophy	Has the patient undergone surgery and anaesthesia in the past?	If general anaesthesia is planned, an anaesthetic opinion should be obtained well in advance of surgery

Ophthalmic preoperative assessment

A detailed and pertinent ophthalmic evaluation is required. Following a past ophthalmic history, the following should be considered:

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1 Visual acuity is usually tested using a Snellen chart despite its limitations (see Ch. 14).

2 Cover test. A heterotropia may indicate amblyopia, which carries a guarded visual prognosis, or the possibility of diplopia if the vision is improved. A squint, usually a divergence, may develop in an eye with poor vision due to cataract, and lens surgery alone may straighten the eye.

3 Pupillary responses. Because a cataract never produces an afferent pupillary defect, its presence implies substantial additional pathology likely to influence the final visual outcome and requires further investigation.

4 Ocular adnexa. Dacryocystitis, blepharitis, chronic conjunctivitis, lagophthalmos, ectropion, entropion and tear film abnormalities may predispose to endophthalmitis and require effective preoperative resolution.

5 Cornea. Eyes with decreased endothelial cell counts (e.g. substantial cornea guttata) have increased vulnerability to postoperative decompensation secondary to operative trauma. Specular microscopy and pachymetry may be helpful in assessing risk, and special precautions should be taken to protect the endothelium (see below).

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6 Anterior chamber. A shallow anterior chamber can render cataract surgery difficult. Recognition of a poorly dilating pupil allows intensive preoperative mydriatic drops, planned mechanical dilatation prior to capsulorhexis and/or intracameral injection of mydriatic. A poor red reflex compromises the creation of an adequate capsulorhexis, but can be largely overcome by staining the capsule with a dye such as trypan blue 0.06% (VisionBlue®).

7 Lens. Nuclear cataracts tend to be harder and may require more power for phacoemulsification, while cortical opacities tend to be softer. Black nuclear opacities are extremely dense and extracapsular cataract extraction rather than phacoemulsification may be the superior option. Pseudoexfoliation indicates a likelihood of weak zonules (look for phakodonesis), a fragile capsule and poor mydriasis.

8 Fundus examination. Pathology such as age-related macular degeneration may affect the visual outcome. Ultrasonography may be required, principally to exclude retinal detachment and staphyloma, in eyes with very dense opacity that precludes fundoscopy.

9 Current refractive status. It is critical to obtain details of the patient’s pre-operative refractive error in order to guide intraocular lens implant (IOL) selection. The keratometry readings (obtained during biometry – see below) should be noted in relation to the refraction, particularly if it is planned to address astigmatism by means of targeted wound placement or a specific adjunctive procedure. It is particularly important to obtain a postoperative refractive result from an eye previously operated upon so that any ‘refractive surprise’, even if minor, can be analysed and taken into account.

Biometry

Biometry facilitates calculation of the lens power likely to result in the desired postoperative refractive outcome; in its basic form this involves the measurement of two ocular parameters, keratometry and axial (anteroposterior) length.

1 Keratometry involves determination of the curvature of the anterior corneal surface (steepest and flattest meridians), expressed in dioptres or in mm of radius of curvature. This is commonly carried out with the interferometry apparatus used to determine axial length (see below), but if this is unavailable or unsuitable manual keratometry (e.g. Javal–Schiøtz keratometer) can be performed.

2 Optical coherence biometry is a non-contact method of axial measurement that utilizes two coaxial low-energy laser beams which are partially coherent and produce an interference pattern (partial coherence interferometry). The Zeiss IOLMaster (Fig. 9.7A) is a complete biometry system which also readily performs keratometry, anterior chamber depth and corneal white-to-white measurement, and is able to calculate IOL power using a range of formulae. Measurements (Fig. 9.7B) have high reproducibility and generally require less skill than ultrasonic biometry (see below). Data storage and A-constant validation are other useful features. Aphakic, pseudophakic and silicone-filled eyes can be measured, with variable tailored settings.

3 A-scan ultrasonography is a generally slightly less accurate method of determining the axial dimension and can be acquired either by direct contact (Fig. 9.7C) or more accurately but with greater technical difficulty by using a water bath. The sound beam must be aligned with the visual axis for maximal precision; each reflecting surface shows up as a spike on the oscilloscope screen (Fig. 9.7D).

4 IOL power calculation formulae. Numerous formulae have been developed which utilize keratometry and axial length to calculate the IOL power required to achieve a given refractive outcome. Some formulae incorporate additional parameters such as anterior chamber depth to optimize the accuracy of prediction. The SRK-T is an example of a commonly used formula for eyes of axial length greater than 22.0 mm. Specific formulae may be superior for very short (generally the Hoffer Q) or long eyes, but research results and opinions vary and it is always wise to take the time to plan individually for an unusual eye, consulting the latest research and recommendations.

5 Previous refractive surgery. Any form of corneal refractive surgery is likely to make a significant difference to the IOL power required for a given refractive outcome, and standard IOL calculations are unsuitable.

6 Contact lenses. If the patient wears soft contact lenses, these may need to be left out for up to a week prior to biometry to allow corneal stabilization; hard/gas permeable lenses may need to be left out for three weeks.

7 Personalized A-constant. If a consistent postoperative refractive deviation is found in most of an individual surgeon’s cases, it is assumed that some aspects of personal surgical (or possibly biometric) technique consistently and similarly influence outcome, and a personalized A-constant can be programmed into biometry apparatus to take this into account.

Fig. 9.7 Biometry (A) IOLmaster; (B) ideal scan; (C) contact A-scan biometry; (D) ultrasonic A-scan display

(Courtesy of D Michalik and J Bolger)

Postoperative refraction

1 Emmetropia is typically the ideal postoperative refraction, though with spectacles needed for close work since a conventional IOL cannot accommodate. Many surgeons aim for a small degree of myopia (about −0.25 D) to offset possible errors in biometry.

2 Contralateral eye. If this has a significant refractive error but is unlikely to require cataract surgery within a few years, the postoperative target for the operated eye might be set for within less than 2.0 D of its fellow, to avoid problems with binocular fusion. In some cases, such as when there is minimal lens opacity in the fellow eye or when ametropia is extreme, the patient can be offered lens surgery to the other eye to facilitate targeting both at emmetropia.

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3 ‘Monovision’ is a concept in which the (usually) non-dominant eye is left at or just less than –2.0 D myopic to allow reading whilst emmetropia is targeted in the dominant eye. This is attractive to some patients, generally those who have previously been using contact lenses or spectacles to achieve monovision.

4 Multifocal lens options use a variety of optical means to attempt to achieve satisfactory near, distance and intermediate vision. Many patients are very satisfied with the results but a significant minority are unhappy, complaining of phenomena such as glare. Highly accurate refractive outcomes, including very limited astigmatism, are necessary for optimal function and a greater likelihood of tolerance.

5 Younger patients. With a conventional monofocal IOL, patients younger than about 50 need to be aware that they will experience the sudden loss of active focusing and that it will often take some time to adjust.

Intraocular lenses

Positioning

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An IOL consists of an optic and the haptics. The optic is the central refracting element, and the haptics the arms or loops which sit in contact with the ocular structures (capsular bag, ciliary sulcus or anterior chamber angle) for stable optimal positioning (centration) of the optic. Modern cataract surgery, with preservation of the capsular ‘bag’, affords positioning of the IOL in the ideal location – ‘in the bag’. Complicated surgery, with rupture of the posterior capsule, may necessitate alternative positioning in the posterior chamber with the haptics in the ciliary sulcus (a 3-piece IOL only, not 1-piece including those with plate haptics, as these may not be stable), or in the anterior chamber (AC) with the haptics supported in the angle – AC positioning requires a specific lens type, an ‘AC-IOL’.

Design

1 Flexible IOLs are now in general use and allow introduction into the eye through a very small incision. For insertion they may be folded in half with special forceps or loaded into an injector delivery system, then unfolded or unrolled inside the eye. Injector-based delivery has become increasingly popular, as it allows introduction without lens contact with the ocular surface, so reducing the risk of bacterial contamination. Injection also allows insertion through a slightly smaller incision than folding. Flexible materials available are discussed below; there seems to be no distinct superiority of one over another, and a combination IOL can also be used.

a Silicone IOLs are available in both loop haptic (1- or 3-piece) and plate haptic (1-piece) conformations, the latter consisting of a roughly rectangular leaf with the optic sited centrally. Silicone IOLs may exhibit greater biocompatibility, exciting less inflammatory reaction, than hydrophobic acrylic IOLs. They may be particularly prone to significant silicone deposition in silicone oil-filled eyes.

b Acrylic IOLs, 3-piece or 1-piece, may be hydrophobic (water content <1%) or hydrophilic, with much higher water content.

• Hydrophobic acrylic materials have a greater refractive index than hydrophilic lenses and are consequently thinner. They tend to produce a greater reaction in uveitic eyes, and some surgeons prefer not to use them in this scenario.

• Hydrophilic acrylic (hydrogel), in theory, offers superior biocompatibility and so should be better tolerated by uveitic eyes. Posterior capsular opacification (PCO) rates are probably higher than with other materials.

c Collamer is composed of collagen, a poly-HEMA based copolymer and a UV-absorbing chromophore. It is marketed principally on the basis of high biocompatibility and a favourable track record.

2 Rigid IOLs are made entirely from polymethylmethacrylate (PMMA). They cannot be folded or injected so require an incision larger than the diameter of the optic, typically 5 mm, for insertion. For economic reasons, they continue to be widely used in developing countries. PCO rates are higher with PMMA lenses than silicone and acrylic. Some surgeons favour heparin-coated (see below) IOLs in uveitic eyes, particularly in children.

3 Sharp/square-edged optics are significantly associated with a lower rate of PCO compared with round-edged optics, and the former is now the predominant design. Lens material seems to have a less important effect than shape on PCO.

4 Blue light filters. Although essentially all IOLs contain ultraviolet light filters, a number also include filters for blue wavelengths, in order to reduce the possibility of damage to the retina.

5 Aspheric optics counteract spherical aberration and improve contrast, particularly in mesopic conditions, and are available in some newer IOLs.

6 Heparin coating reduces the attraction and adhesion of inflammatory cells, and this may have particular application in eyes with uveitis. However, there is no clear evidence about whether heparin-surface modification is clinically beneficial, and indeed about which IOL material is superior for use in cataract surgery on eyes with uveitis.

7 Multifocal IOLs aim to provide clear vision over a range of focal distances. So-called accommodative IOLs attempt to flex and thereby alter focal length but in practice the amplitude of accommodation is slight. Pseudoaccommodative IOLs achieve their purpose by refractive or diffractive means.

8 Toric IOLs have an integral cylindrical refractive component to compensate for pre-existing corneal astigmatism. The main potential problem is rotation within the capsular bag, which occurs in 10–20%, following which surgical repositioning may be carried out.

9 Adjustable IOLs allow the alteration of refractive power following implantation. One version uses low-level ultraviolet irradiation at the slit-lamp about a week after surgery to induce polymerization of its constituent molecules in specific patterns with precise spherical and cylindrical (astigmatism) correction.

Anaesthesia

The vast majority of cataract surgery is performed under local anaesthesia (LA) although general anaesthesia is required in some circumstances such as children and many young adults, very anxious patients, some patients with learning difficulties, epilepsy, dementia and those with a head tremor.

1 Sub-Tenon block involves inserting a blunt-tipped cannula through an incision in the conjunctiva and Tenon capsule 5 mm from the limbus inferonasally, and passing it through the sub-Tenon space (Fig. 9.8A). The anaesthetic is injected beyond the equator of the globe (Fig. 9.8B). Although anaesthesia is good and complications minimal, akinesia is variable. Chemosis and subconjunctival haemorrhage are common but penetration of the globe is extremely rare.

2 Peribulbar block is given through the skin or conjunctiva with a 1-inch (25-mm) needle (Fig. 9.9A and B). It generally provides effective anaesthesia and akinesia. Penetration of the globe is a very severe, though extremely rare, complication, and for this reason peribulbar is avoided, or approached with great caution, in longer eyes (which also tend to have a larger equatorial diameter).

3 Topical anaesthesia involves drops or gel (proxymetacaine 0.5%, tetracaine 1% drops, lidocaine 2% gel) which can be augmented with intracameral preservative-free lidocaine 0.2%–1%, usually during hydrodissection; combined viscoelastic/lidocaine preparations are also commercially available. Although analgesia is generally adequate, it tends to be less effective than peribulbar or sub-Tenon blocks. Despite the absence of akinesia most patients can cooperate adequately.

Fig. 9.8 Sub-Tenon anaesthesia. (A) Dissection; (B) infiltration

Fig. 9.9 Peribulbar anaesthesia. (A) Insertion of needle; (B) injection

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Phacoemulsification

Introduction

Phacoemulsification (‘phaco’) has become the preferred method of cataract extraction over the last 15 years. The smaller incision of phacoemulsification is associated with little induced postoperative astigmatism and early stabilization of refraction (usually 3 weeks for 3.0 mm incisions but less for sub-2.5 mm incisions). Postoperative wound-related problems such as iris prolapse have been almost eliminated. One disadvantage of phaco is that it requires complex machinery to break up the lens nucleus and remove it through a small incision. Considerable training and practice is required to learn the techniques adequately.

Phacodynamics

The surgeon must understand the machine dynamics and the interaction of fluidics in treating different forms of cataract. The various machines behave differently but the basic mechanism is similar. Choosing appropriate settings makes surgery safer and easier.

1 Level of irrigating bottle is measured from the level of the patient’s eye. The purpose of setting the bottle at a specific height is to maintain a stable eye at a reasonable intraocular pressure. The infusion flow is proportional to the height of the bottle and is dependent on gravity.

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2 Aspiration flow rate (AFR) refers to the volume of fluid removed from the eye in cc/minute. For a higher AFR the bottle must be elevated to compensate for increased fluid loss. High AFR results in attraction of lens material towards the phaco tip, with faster vacuum build-up and swifter removal of lens matter but with less power. Adjustment to a high AFR should be avoided by an inexperienced surgeon to reduce the chance of mishap.

3 Vacuum, measured in mmHg, is generated during occlusion when the pump is attempting to aspirate fluid. Vacuum helps to hold nuclear material and provides the ability to manipulate lens fragments. High vacuum can also decrease the total power required to remove the lens.

4 Surge. When occlusion is broken pent up energy in the system results in surge. This is undesirable as it may result in collapse of the anterior chamber and capsular rupture.

Pumps

1 Peristaltic flow pumps pull liquid and lens material into the phaco tip by milking fluid-filled tubing over rollers inside the cassette attached to the phaco machine. The speed at which this is performed is determined by the speed of rotation of the rollers. However, in order for the pump to generate vacuum, occlusion of the tip is required. As vacuum builds to the pre-set level, the pump slows down until it stops when the required vacuum is achieved.

2 The Venturi pump creates a negative pressure in a vessel by passing compressed gas across its entrance, generating vacuum. This has the practical effect of synchronizing vacuum and AFR. Depression of the foot pedal increases vacuum towards the preset level independent of occlusion, and tip vacuum is therefore always available.

Handpiece

The phaco handpiece (Fig. 9.10A) contains a series of piezoelectric crystals which act as rapid switching devices, causing the tip to vibrate at ultrasonic frequencies. The tip itself consists of a hollow titanium needle 0.7–1.1 mm in diameter with an enclosing sleeve (Fig. 9.10B) to protect the cornea from thermal and mechanical damage. Differently-shaped phaco needles have various characteristics in terms of cutting and holding nuclear material. Emulsification of the lens is the result of the following phenomena:

1 Jackhammer pneumatic drill effect is probably the most important.

2 Cavitation resulting from the swift movement of solid in a liquid. At the end of each oscillation backstroke, the tip retracts and creates a vacuum which causes cavitation bubbles. The bubbles implode and release large amounts of energy.

3 Acoustic shock wave generated by the excursion of the phaco tip.

4 Impact of the fluid particle wave as the tip impacts on aqueous. In softer cataracts it is possible to see this in action by removing tissue without direct contact.

Fig. 9.10 (A) Phaco handpiece with tip; (B) phaco tip with sleeve

Viscoelastics

Viscoelastics are biopolymers whose main constituents are glycosaminoglycans and hydroxypropylmethylcellulose. All have the propensity to cause raised intraocular pressure unless carefully removed at the end of surgery.

The main types are:

1 Cohesive (e.g. Healon®, Healon GV® and Provisc®)

• Long chains and high molecular weight.

• Easy to remove.

• Used to create and maintain intraocular spaces, for example to maintain the AC during capsulorhexis and inflation of the capsular bag to facilitate introduction of the IOL.

2 Dispersive (e.g. Viscoat®)

• Low molecular weight and a tendency to break up.

• Used to coat and protect the endothelium.

• Can also be used to create and maintain space, forming compartments.

• More difficult to remove than cohesive viscoelastics.

3 Adaptive (e.g. Healon 5®) displays properties of both cohesive and dispersive agents.

4 Clinical use may also include:

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• The ‘soft shell’ technique involves the injection of a dispersive followed by a cohesive viscoelastic underneath. The former adheres to and protects the endothelium. Some surgeons use this routinely for all eyes, others for eyes at higher risk of corneal decompensation such as those with a guttate cornea.

• In small pupils a high molecular weight cohesive viscoelastic (e.g. Healon GV) will push the iris away from the lens and help to induce mydriasis.

• Can be used to break posterior synechiae with minimal trauma.

• May be useful to dissect cortex away from the lens capsule to minimize traction on fragile zonular ligaments.

• If a capsulorhexis shows signs of running out to the periphery, injecting a cohesive viscoelastic will flatten the anterior capsule, aiding the exertion of a centrally-directed vector (and expanding the pupil).

• In small posterior capsular tears a dispersive viscoelastic will push the vitreous back into the posterior chamber and plug the capsular defect, facilitating cortex removal.

• Higher molecular weight viscoelastics tend to promote iris prolapse in shallow anterior chambers.

Technique

It is beyond the scope of this book to describe the technique in detail; the following are the basic steps:

1 Preparation

a Topical anaesthetic is instilled into the conjunctival sac prior to antiseptic application.

b Povidone-iodine 5% or chlorhexidine is instilled into the conjunctival sac (Fig. 9.11A) and is also used to paint the skin of the eyelids prior to draping (Fig. 9.11B), ensuring thorough eyelash application; the antiseptic should be left to work for a minimum of 3 minutes.

c Careful draping is performed, ensuring that the lashes and lid margins are isolated from the surgical field, and a speculum is inserted (Fig. 9.11C).

2 Incisions

a A side port incision is made around 60° to the left (in right-handed surgeons) of the main incision; some surgeons prefer two side ports approximately 180° apart.

b The main corneal incision may be clear corneal or limbal (Fig. 9.12A); many surgeons locate the incision on the steepest corneal axis, though others prefer consistent siting. Temporal incisions may be associated with a slightly higher risk of endophthalmitis.

c Viscoelastic is injected into the anterior chamber.

3 Continuous curvilinear capsulorhexis (Fig. 9.12B) is performed with a cystotome, a bent hypodermic needle and/or capsule forceps and involves two movements:

a Shearing in which a tangential vector force is applied along the direction of the tear.

b Ripping in which a centripetal vector force strains and tears the capsule.

4 Hydrodissection is performed to separate the nucleus and cortex from the capsule so that the nucleus can be more easily and safely rotated.

a A 26-gauge blunt cannula with fluid is inserted just beneath the edge of the rhexis and fluid is injected gently under the capsule (Fig. 9.12C).

b A hydrodissection wave should be seen provided there is a good red reflex.

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c The phaco probe is inserted and superficial cortex and epinucleus are aspirated.

5 Four quadrant (’divide and conquer’) technique for removal of the nucleus is a very widely used, safe technique.

a ’Sculpting’ is performed with the probe to create a groove (Fig. 9.12D).

b The nucleus is rotated and a second groove is made at a right angle to the first.

c The probe and second instrument are engaged in opposite walls of the groove and the nucleus is cracked by applying force in opposite directions (Fig. 9.12E).

d The nucleus is rotated 90° and a crack made in the perpendicular groove in a similar manner.

e Each of the four quadrants is emulsified and aspirated in turn (Fig. 9.12F).

6 Nuclear phaco chop takes greater experience, but has the advantage of generally requiring lower total phaco energy.

a In horizontal chopping a blunt-tipped chopper is placed horizontally underneath the capsule and rotated vertically as the equator is reached.

b Vertical chopping is performed with a pointed-tip chopper which does not need to pass beyond the capsulorhexis.

c The nucleus is chopped into several pieces each of which is emulsified and aspirated.

7 Cortical clean up. The cortical fragments are engaged by vacuum, pulled centrally and aspirated (Fig. 9.13A). Some surgeons prefer a manual aspiration method, producing vacuum with a hand-held syringe (e.g. Simcoe cannula), or a bimanual automated method.

8 Insertion of IOL

a The capsular bag is filled with viscoelastic (Fig. 9.13B).

b The corneal incision is enlarged (Fig. 9.13C).

c The IOL is inserted into a cartridge for injection which is loaded into an injector handset. The tip of the cartridge is introduced through the section (Fig. 9.13D) and the IOL slowly injected into the eye, with careful unrolling (Fig. 9.13E). Alternatively, the IOL is folded and inserted directly into the eye.

d If necessary the IOL is centred by dialling (Fig. 9.13F).

9 Completion

a Viscoelastic is aspirated.

b The side port incisions may be sealed with a jet of saline.

c Common anti-infection measures at the end of surgery may include a drop of topical antibiotic, a subconjunctival injection of steroid and antibiotic, and/or an intracameral (anterior chamber) antibiotic.

Fig. 9.11 Preparation. (A) Povidone-iodine 5% is instilled; (B) skin is painted; (C) drapes isolate the eyelids from the operating field with insertion of a speculum.

Fig. 9.12 Four quadrant (’divide and conquer’) phacoemulsification. (A) Corneal incision; (B) capsulorhexis; (C) hydrodissection; (D) nucleus is grooved; (E) nucleus is cracked; (F) each nuclear quadrant is emulsified and aspirated

Fig. 9.13 Completion of phacoemulsification. (A) Cortical lens matter is pulled centrally and aspirated: (B) injection of viscoelastic into the capsular bag; (C) incision is enlarged; (D) cartridge nozzle with IOL is introduced through the incision; (E) IOL is slowly injected into the eye; (F) IOL is dialled into position if necessary

Small incision manual cataract surgery

Small incision manual cataract surgery is an effective alternative to phacoemulsification in countries where very high volume surgery with inexpensive instrumentation is required. The procedure is fast and has a low rate of complications, and can be performed on a dense cataract. The technique is as follows:

a A self-sealing partial thickness scleral tunnel is dissected and the anterior chamber is entered (Fig. 9.14A).

b Capsulorhexis is performed (Fig. 9.14B).

c Hydrodissection is performed and the nucleus is partly prolapsed into the anterior chamber (Fig. 9.14C).

d A small hook is inserted between the posterior capsule and nucleus, and the nucleus extracted (Fig. 9.14D). It is also possible to extract the nucleus with an irrigating vectis.

e The epinucleus and residual cortex are aspirated with a Simcoe cannula (Fig. 9.14E).

f The IOL is inserted (Fig. 9.14F).

Fig. 9.14 Small incision manual cataract surgery. (A) Anterior chamber is entered; (B) capsulorhexis; (C) prolapse of nucleus into anterior chamber; (D) expression of nucleus; (E) cortical cleanup; (F) IOL in place

(Courtesy of A Hennig)

Operative complications

Rupture of the posterior lens capsule

Capsular rupture may be accompanied by vitreous loss, posterior migration of lens material, and rarely expulsive haemorrhage. Sequelae to vitreous loss, particularly if inappropriately managed, include chronic cystoid macular oedema, retinal detachment, endophthalmitis, updrawn pupil, uveitis, vitreous touch, vitreous wick syndrome, glaucoma and posterior dislocation of the IOL.

1 Signs

• Sudden deepening or shallowing of the anterior chamber and momentary pupillary dilatation.

• The nucleus falls away and cannot be approached by the phaco tip.

• Vitreous aspirated into the phaco tip often manifests with a marked slowing of lens material aspiration.

• The torn capsule or vitreous gel may be directly visible.

2 Management depends on the magnitude of the tear, the size and type of any residual lens material, and the presence or absence of vitreous prolapse. The main principles of management are as follows:

a Dispersive viscoelastic such as Viscoat may be injected behind nuclear material with the purpose of expressing it into the anterior chamber and of preventing anterior herniation of additional vitreous. If a complete or nearly-complete nucleus remains, conversion to extracapsular extraction may be considered. A vitrector can be employed at this point (see below) to remove vitreous entangled with nuclear fragments.

b The incision may be enlarged, if necessary, and a lens glide (Sheets’) may be passed behind the lens fragments to cover the capsular defect (Fig. 9.15), although it is important to confirm that vitreous has first been displaced or removed and will not be put under traction.

c Residual nuclear fragments are carefully removed by phaco with low bottle height and low AFR, or if large by viscoexpression after extending the main wound.

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d Once nuclear remnants have been removed, the anterior chamber is gently filled with a cohesive viscoelastic and a manual aspiration cannula with irrigation turned off used to gently aspirate residual cortex, topping up the AC with viscoelastic as necessary.

e All vitreous is removed from the anterior chamber and the wound with a vitrector placed deep to the capsular tear. A bimanual technique, with separate of the infusion and cutting instruments, is viewed as superior by many, as vitreous is not pushed away from the cutter (the position of the infusion cannula is kept high and that of the cutter low). The main practical difficulty is visualization of the vitreous gel, and this can be enhanced by the instillation of trypan blue 0.06% (VisionBlue) or 0.1 mL of 40 mg/mL of triamcinolone (shake well before use). The infusion bottle height should be sufficient to keep the anterior chamber maintained without intermittent shallowing.

f A small posterior capsular tear may allow careful in-the-bag implantation of a PC-IOL and it may be possible to convert a small tear into a posterior capsulorhexis.

g Even a large tear will usually allow ciliary sulcus placement of a three piece PC-IOL. The haptics should be placed at 90° to a peripheral tear, and should be angulated posteriorly to maximize iris clearance. If possible, after placing the IOL in the sulcus the optic should be captured within an intact capsulorhexis of slightly smaller diameter by depressing each side of the optic beneath the capsulorhexis in turn. With capsulorhexis capture, the originally planned IOL power, or possibly 0.5 D less, can be used; without capture, the power is reduced by 0.5–1.0 D.

h Acetylcholine (Miochol®) is used to constrict the pupil following implantation of a PC-IOL or prior to inserting an AC-IOL.

i Insufficient capsular support may necessitate implantation of an AC-IOL with the aid of a glide (Fig. 9.16); an iridectomy is needed to prevent pupillary block. AC-IOLs are associated with a higher risk than PC-IOLs of complications including bullous keratopathy, hyphaema, iris tuck and pupillary irregularities. An iris or trans-sclerally sutured posterior chamber IOL is an alternative.

j A suture should be used to secure the wound, even if it seems adequately self-sealed.

Fig. 9.15 Lens glide supporting nuclear fragments following rupture of the posterior capsule

(Courtesy of R Packard)

Fig. 9.16 Insertion of an anterior chamber IOL. (A) Glide is inserted; (B) IOL is coated with viscoelastic; (C) IOL is inserted; (D) incision is sutured

Posterior loss of lens fragments

Dislocation of fragments of lens material into the vitreous cavity after zonular dehiscence or posterior capsule rupture is rare but potentially serious as it may result in glaucoma, chronic uveitis, retinal detachment and chronic cystoid macular oedema. Initially, any uveitis or raised intraocular pressure must be treated. It may be reasonable to adopt a conservative approach for small fragments, but larger fragments, certainly a quadrant or more, will virtually always require removal by pars plana vitrectomy.

Posterior dislocation of IOL

Dislocation of an IOL into the vitreous cavity (Fig. 9.17A) is a rare but serious complication particularly if accompanied by loss of lens material (Fig. 9.17B). If the IOL is left in the posterior segment it may lead to vitreous haemorrhage, retinal detachment, uveitis and chronic cystoid macular oedema. Treatment involves pars plana vitrectomy with removal, repositioning or exchange of the IOL depending on the extent of capsular support.

Fig. 9.17 (A) IOL on the retina; (B) IOL and large nuclear fragments in vitreous

(Courtesy of S Milewski)

Suprachoroidal haemorrhage

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A suprachoroidal haemorrhage involves a bleed into the suprachoroidal space from a ruptured long or short posterior ciliary artery. If sufficiently severe it may result in extrusion of intraocular contents (‘expulsive’ haemorrhage). It is a dreaded complication, but extremely rare (0.04%) with phacoemulsification. Contributing factors include advanced age, glaucoma, increased axial length, systemic cardiovascular disease, vitreous loss, and conversion from phacoemulsification to ECCE. A high intraoperative index of suspicion is critical, and if there is any suggestion of a suprachoroidal haemorrhage the operation should be terminated and the incision sutured immediately.

1 Signs in chronological order

a Progressive shallowing of the anterior chamber, increased intraocular pressure and prolapse of the iris.

b Vitreous extrusion, loss or partial obscuration of the red reflex and the appearance of a dark mound behind the pupil.

c In severe cases, posterior segment contents may be extruded into the anterior chamber and through the incision.

2 Immediate treatment

a The AC is filled with a cohesive viscoelastic and the incision is sutured.

b The viscoelastic should be left in the eye to raise the intraocular pressure and tamponade the bleeding vessel.

c IOP-lowering medication such as oral acetazolamide is given to address the resultant pressure spike.

d Intravenous mannitol may be given if necessary although reducing the IOP too rapidly should be avoided.

e Postoperatively, topical and systemic steroids should be used aggressively to reduce intraocular inflammation.

3 Subsequent treatment, if spontaneous absorption fails to occur, involves drainage of large ‘kissing’ haemorrhages that can be performed 7–14 days later, by which time liquefaction of blood clot has taken place. The visual prognosis for large haemorrhages is highly variable; prolonged chorioretinal apposition (>14 days) has a poor prognosis. Pars plana vitrectomy may be considered when the retina appears adherent or detached, though kissing haemorrhages may resolve spontaneously without immediately apparent retinal problems. If appropriate, completion of cataract surgery may be considered after a further 1–2 weeks.

Acute postoperative endophthalmitis

Pathogenesis

The estimated incidence of acute endophthalmitis following cataract surgery is approximately 0.3%. Toxins produced by the infecting bacteria and the host inflammatory responses cause rapid and irreversible photoreceptor damage, and these effects can continue long after the ocular contents have been rendered sterile.

1 Possible risk factors include operative complications such as posterior capsule rupture, prolonged procedure time, combined procedure (e.g. with vitrectomy), clear corneal sutureless incision, temporal incision, wound leak on the first day, delaying postoperative topical antibiotics until the day after surgery, topical anaesthesia, adnexal disease and diabetes.

2 Pathogens. About 90% of isolates are Gram-positive and 10% Gram-negative. In order of frequency they include:

• Coagulase-negative staphylococci (S. epidermidis).

• Other Gram-positive organisms (S. aureus and Streptococcus spp.).

• Gram-negative organisms (Pseudomonas spp. and Proteus spp.).

3 The source of infection usually cannot be identified with certainty. It is thought that the flora of the eyelids and conjunctiva are the most frequent source, including contamination via incisions in the early postoperative stages. Other potential sources include contaminated solutions and instruments, environmental air, and the surgeon and other operating room personnel.

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Prophylaxis

Because of the low rate of endophthalmitis it is very difficult to prove that any method of prophylaxis is effective or superior to any other. The following are likely to be beneficial:

1 Instillation of 5% povidone-iodine into the conjunctival fornices and leaving this undisturbed for at least 3 minutes prior to surgery.

2 Scrupulous preparation of the surgical site, with re-draping if eyelash coverage is inadequate.

3 Treatment of pre-existing infections such as blepharitis, conjunctivitis, chronic dacryocystitis and infection in the contralateral eye or socket.

4 Prophylactic antibiotics

• Pre-operative topical fluoroquinolone antibiotics are frequently given in regimens from 1 hour to 3 days before surgery.

• Intracameral cefuroxime (1 mg in 0.1 mL) injected into the AC at the end of surgery.

• Postoperative subconjunctival injection can achieve bactericidal levels in the anterior chamber for at least 1–2 hours.

• Newer-generation quinolones such as moxifloxacin penetrate the eye effectively to give concentrations inhibitory to bacterial growth.

5 Early resuturing of leaking wounds rather than observation may be prudent.

6 Reviewing personal surgical practice to eliminate potentially risk-prone elements, particularly if a significant rate of endophthalmitis is encountered.

Clinical features

1 Symptoms are pain and visual loss.

2 Signs vary according to severity.

• Eyelid swelling, chemosis, conjunctival injection and discharge.

• A relative afferent pupillary defect is common.

• Corneal haze (Fig. 9.18A)

• Fibrinous exudate and hypopyon (Fig. 9.18B).

• Vitritis with an impaired view of the fundus (Fig. 9.18C).

• Severe vitreous inflammation and debris (Fig. 9.18D) with loss of the red reflex.

Fig. 9.18 Acute bacterial endophthalmitis. (A) Corneal haze; (B) fibrinous exudate and hypopyon; (C) vitreous haze and impaired fundus view; (D) severe vitritis

(Courtesy of S Tuft – figs A, B and D)

Differential diagnosis

If there is any doubt about the diagnosis, treatment should be that of infectious endophthalmitis. Early recognition leads to a better outcome.

1 Retained lens material in the anterior chamber or vitreous may precipitate a severe uveitis, corneal oedema and raised intraocular pressure.

2 Vitreous haemorrhage, especially if blood in the vitreous is depigmented.

3 Postoperative uveitis. A confident diagnosis of infection is not always straightforward. If signs of inflammation are mild a trial of topical steroid therapy and early review (6–24 hours) is appropriate. If there is no substantial improvement management should be that of endophthalmitis.

4 Toxic reaction to the use of inappropriate or contaminated irrigating fluid or viscoelastic. An intense fibrinous reaction with corneal oedema may develop although other signs of infectious endophthalmitis are absent. Treatment is with intensive topical steroids combined with cycloplegics. Corneal decompensation may be permanent.

5 Complicated or prolonged surgery may result in corneal oedema and uveitis.

Identification of pathogens

Samples for culture should be obtained from aqueous and vitreous to confirm the diagnosis. However, negative culture does not necessarily rule out infection and treatment should be continued. An operating theatre with experienced staff is the best setting, but samples can be taken in a minor procedures operating room if necessary to avoid delay, making sure that all equipment is available prior to starting.

1 B-scan ultrasound should be performed prior to vitreous sampling to exclude retinal detachment if there is no clinical view.

2 Preparation

• Povidone iodine 5% is instilled.

• Topical and subconjunctival, sub-Tenon’s or peribulbar anaesthesia is administered.

• The eye is draped as for cataract surgery, with insertion of a speculum.

3 Aqueous samples

• Between 0.1 mL and 0.2 mL of aqueous is aspirated via a limbal paracentesis using a 25-G needle on a tuberculin syringe.

• The syringe is capped and labelled.

4 Vitreous samples are more likely to yield a positive culture than aqueous.

• A 2 mL syringe and a 23-G needle may be used, or optimally a disposable vitrector (Fig. 9.19A).

• The distance from the limbus for the scleral incision is measured with callipers and marked (Fig. 9.19B): 3 mm (pseudophakic eye), 4 mm (phakic eye).

• 0.2–0.4 mL is aspirated from the mid-vitreous cavity (Fig. 9.19C). If using a disposable vitrector, cap off the tubing securely and place in a specimen bag. Do not disconnect the vitrector from its tubing.

6 Conjunctival swabs may be taken as well, as significant culture may be helpful in the absence of a positive culture from intraocular samples.

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7 Microbiology. Specimens should be sent to the microbiology laboratory immediately; most prefer to receive a sample in the apparatus used for acquiring the specimen and will divide the specimen for microscopy and culture. Polymerase chain reaction (PCR) can be helpful in identifying unusual organisms, the cause of culture negative disease, and organisms after antibiotic treatment has been started. However, its high sensitivity means that contamination can lead to false positive results.

Fig. 9.19 Management of acute endophthalmitis. (A) Mini-vitrector for obtaining vitreous samples; (B) callipers measuring distance from limbus; (C) vitreous samples obtained with vitrector; (D) intravitreal antibiotic injection

Treatment

1 Intravitreal antibiotics are the key to management because they achieve levels above the minimum inhibitory concentration of most pathogens, and these are maintained for days. They should be administered immediately after culture specimens have been obtained. Two antibiotics commonly used in combination are ceftazidime, which will kill most Gram-negative organisms (including Pseudomonas aeruginosa) and vancomycin to address coagulase-negative and coagulase-positive cocci (including methicillin-resistant S. aureus).

• The concentrations are ceftazidime 2 mg in 0.1 mL and vancomycin 2 mg in 0.1 mL; amikacin 0.4 mg in 0.1 mL can be used as an alternative to ceftazidime in patients allergic to penicillin but is more toxic to the retina. See Table 9.2 for details of preparation.

• The antibiotics are injected slowly into the mid-vitreous cavity using a 25-G needle (Fig. 9.19D).

• After the first injection has been given, the syringe may be disconnected but the needle left inside the vitreous cavity so that the second injection can be given through the same needle. Alternatively, a second needle can be used.

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2 Periocular antibiotic injections are often given but are of doubtful additional benefit if intravitreal antibiotics have been used. Suggested doses are vancomycin 50 mg and ceftazidime 125 mg (or amikacin 50 mg).

3 Topical antibiotics are of limited benefit and are often used only 4–6 times daily in order to protect the fresh wounds from contamination. Vancomycin 5% (50 mg/mL) or ceftazidime 5% (50 mg/mL) applied intensively may penetrate the cornea in therapeutic levels. Third or fourth generation fluoroquinolones achieve effective levels in the aqueous and vitreous, even in uninflamed eyes, and may be considered.

4 Oral antibiotics. Fluoroquinolones penetrate the eye well and moxifloxacin 400 mg daily for 10 days is recommended; clarithromycin 500 mg twice daily may be helpful for culture negative infections. Evidence suggests these may attack bacterial biofilm.

5 Oral steroids. The rationale for the use of steroids is to limit the destructive complications of the inflammatory process. Prednisolone 1 mg/kg daily should be started in severe cases after 12–24 hours provided fungal infection has been excluded from examination of smears. Beware contraindications, prescribe gastric protection (e.g. lansoprazole 30 mg once daily) and monitor appropriately including baseline blood tests; if necessary request general medical advice.

6 Periocular steroids. Dexamethasone or triamcinolone should be considered if systemic therapy is contraindicated.

7 Topical dexamethasone 0.1% 2-hourly initially for anterior uveitis.

8 Topical mydriatic such as atropine 1% twice daily.

9 Intravitreal steroids may reduce inflammation in the short term but they do not influence the final visual outcome; some studies even suggest a detrimental effect. Conversely, improvement in outcome in some bacterial sub-groups has been reported.

10 Pars plana vitrectomy. The Endophthalmitis Vitrectomy Study (EVS) showed a benefit for immediate pars plana vitrectomy in eyes with a visual acuity of perception of light (NOT hand movements vision or better) at presentation, with a 50% reduction in severe visual loss. If vitrectomy is not readily available, it is prudent to give intravitreal antibiotics in the interim. The conclusions of the EVS in post-cataract surgery eyes cannot readily be extrapolated to other forms of endophthalmitis.

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Table 9.2 Preparation of antibiotics for intravitreal injection

Ceftazidime (broad spectrum, including Pseudomonas)

A) Begin with a 500 mg ampoule.

B) Add 10 mL water for injection (WFI) or saline and dissolve thoroughly (for a 250 mg vial add 5 mL WFI or saline, for a 1 g vial add 20 mL WFI or saline).

C) Draw up 1 mL of the solution, containing 50 mg of antibiotic.

D) Add 1.5 mL WFI or saline giving 50 mg in 2.5 mL.

E) Draw up about 0.2 mL (excess to facilitate priming) into a 1 mL syringe. When ready to inject fit the Rycroft cannula or the needle to be used, and discard all but 0.1 mL (contains 2 mg of antibiotic) for injection.

Vancomycin (action primarily against Gram-positive organisms)

Only saline, not WFI, should be used with vancomycin

As A–E above, again preferably starting with a 500 mg ampoule.

Amikacin (alternative to ceftazidime; as carries a higher risk of retinal infarction, use only if well-defined penicillin or cephalosporin allergy); lower intravitreal dose than ceftazidime and vancomycin

Note different dilution procedure to ceftazidime and vancomycin

A) Presentation: vial contains 500 mg of amikacin in 2 mL of solution.

B) Use a 2.5 mL syringe to draw up 1 mL of amikacin solution then 1.5 mL of WFI.

C) Inject 0.4 mL of the solution, containing 40 mg of antibiotic, into a 10 mL syringe and dilute to 10 mL (giving 4 mg per mL).

E) Draw up about 0.2 mL (excess to facilitate priming) into a 1 mL syringe. When ready to inject fit the Rycroft cannula or the needle to be used, and discard all but 0.1 mL (contains 0.4 mg of antibiotic) for injection.

Subsequent management

Subsequent management proceeds according to culture results and clinical findings. Ultrasonography may be useful in assessing response to treatment.

1 Signs of improvement include contraction of fibrinous exudate and reduction of anterior chamber cellular activity and hypopyon. In this situation treatment is not modified irrespective of culture results.

2 If the clinical signs are worsening after 48 hours antibiotic sensitivities should be reviewed and therapy modified accordingly. Par plana vitrectomy should be considered if not previously performed. Intravitreal antibiotics can be repeated after 2 days; if amikacin has previously been used, repeated administration should probably be avoided to reduce the risk of retinal toxicity.

3 The outcome is related to the duration of the infection prior to treatment and the virulence of organisms.

• If visual acuity at presentation is light perception 30% of eyes achieve 6/12 following treatment. If visual acuity is better than light perception this figure increases to 60%.

• Infection with Bacillus cereus and streptococci has a poor visual outcome despite aggressive and appropriate therapy, with 70% and 55%, respectively, achieving a final visual acuity of 6/60 or less. This poor visual outcome may be related to early retinopathy from exotoxins.

4 Late problems

a Persistent vitreous opacities. Aggressive and extended topical, periocular and, if necessary, oral steroid treatment will often lead to resolution. Vitrectomy can be considered if unresolving and severe.

b Maculopathy in the form of epimacular membranes, cystoid oedema and ischaemia.

c Hypotony. Wound leak should be excluded and persistent inflammation addressed. Choroidal effusions should be identified and drained if necessary. Retinal detachment and anterior vitreous membranes may require vitrectomy.

d Other problems include chronic uveitis, secondary glaucoma, retinal detachment and phthisis.

Delayed-onset postoperative endophthalmitis

Pathogenesis

Delayed-onset endophthalmitis following cataract surgery develops when an organism of low virulence becomes trapped within the capsular bag (’saccular endophthalmitis’). Organisms can become sequestered within macrophages, protected from eradication but with continued expression of bacterial antigen.

It has an onset ranging from 4 weeks to years (mean of 9 months) postoperatively and typically follows uneventful cataract extraction with a posterior chamber intraocular lens. It may rarely be precipitated by Nd:YAG laser capsulotomy, which releases the organism into the vitreous. The infection is caused most frequently by P. acnes and occasionally S. epidermidis, Corynebacterium spp. or Candida parapsilosis.

Diagnosis

1 Presentation is with painless mild progressive visual deterioration which may be associated with floaters.

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2 Signs

• Low-grade anterior uveitis, sometimes with mutton-fat keratic precipitates (Fig. 9.20A).

• The inflammation initially responds well to topical steroids (Fig. 9.20B), but recurs when treatment is stopped and eventually becomes steroid resistant (Fig. 9.20C).

• Vitritis is common but hypopyon infrequent.

• An enlarging capsular plaque composed of organisms sequestrated in residual cortex within the peripheral capsular bag is characteristic (Fig. 9.20D).

• Gonioscopy under mydriasis may identify an equatorial plaque.

3 Initial management involves a 10–14 day course of oral moxifloxacin; clarithromycin is an alternative.

4 Investigations consisting of cultures or aqueous and vitreous should be considered, if oral antibiotics are ineffective. Anaerobic culture should be requested if P. acnes infection is suspected, and isolates may take 10–14 days to grow. The detection rate can be greatly improved with the use of polymerase chain reaction (PCR).

5 Treatment if persistent

• Intravitreal antibiotics alone are usually unsuccessful in resolving the infection.

• Removal of the capsular bag, residual cortex and IOL, requiring pars plana vitrectomy. Secondary IOL implantation may be considered at a later date. Intravitreal antibiotics are combined: vancomycin (1 mg in 0.1 mL) is the antibiotic of choice and can also be irrigated into any capsular remnant. P. acnes is also sensitive to methicillin, cefazolin and clindamycin.

Fig. 9.20 Delayed-onset postoperative endophthalmitis. (A) Anterior uveitis with mutton-fat keratic precipitates; (B) fewer keratic precipitates following topical steroid therapy; (C) severe recurrence 2 weeks following cessation of steroid therapy; (D) white plaque within the capsular bag

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Posterior capsular opacification

Visually significant posterior capsular opacification (PCO) is the most common late complication of uncomplicated cataract surgery. Apart from reducing visual acuity, PCO may impair contrast sensitivity, cause difficulties with glare or give rise to monocular diplopia. The incidence of PCO is reduced when the capsulorhexis opening is in complete contact with the anterior surface of the IOL. PMMA (and probably to a lesser extent hydrogel) IOLs are particularly prone to PCO, but otherwise implant design is more important than material; notably, a square edge to the optic appears to inhibit PCO.

Signs

1 Elschnig pearls (bladder cells, Wedl cells) are caused by the proliferation and migration of residual equatorial epithelial cells along the posterior capsule at the site of apposition between the remnants of the anterior capsule and the posterior capsule. They impart a vacuolated appearance to the posterior capsule, best visualized on retroillumination (Fig. 9.21A). This is the most frequently seen type of opacification and is related to the patient’s age. It is extremely common in children if a posterior capsulorhexis is not performed at the time of surgery.

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2 Capsular fibrosis (Fig. 9.21B), due to fibrous metaplasia of epithelial cells, is less common and usually appears earlier than Elschnig pearls.

Fig. 9.21 Posterior capsular opacification. (A) Elschnig pearls; (B) capsular fibrosis; (C) appearance following laser capsulotomy; (D) laser pitting of the IOL

(Courtesy of P Gili – figs A and B; R Packard – fig. C; R Curtis – fig. D)

Treatment

Treatment involves the creation of an opening in the posterior capsule with the Nd:YAG laser.

1 Indications for capsulotomy include:

• Diminished visual acuity.

• Diplopia or glare secondary to capsular wrinkling.

• Inadequate fundus view impairing diagnosis, monitoring or treatment of retinal pathology.

2 Technique. Safe and successful laser capsulotomy involves accurate focusing and using the minimum energy required. Laser power is initially set at 1 mJ/pulse, and may be increased if necessary. A series of punctures are applied in a cruciate pattern using single-pulse shots, the first puncture aimed at the visual axis. An opening of about 3 mm is usually adequate (Fig. 9.21C), but larger capsulotomies may be necessary for retinal examination or photocoagulation.

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3 Complications are not usually associated with identifiable risk factors. The number of laser pulses and the energy level are probably not related to their development, although it is prudent to use minimum possible total energy.

• Damage to the IOL (‘pitting’ – Fig. 9.21D) may occur if the laser is poorly focused. Although undesirable, a few laser marks on the IOL do not alter visual function or impair ocular tolerance of the IOL.

• Cystoid macular oedema is an occasional complication and may develop months after capsulotomy. It is less common when capsulotomy is delayed for 6 months or more after cataract surgery.

• Rhegmatogenous retinal detachment is rare, though more common in high myopes, and may occur several months after capsulotomy.

• Intraocular pressure elevation, which is mild and transient, is usually innocuous. However, sustained elevation above precapsulotomy levels may occur, especially in patients with established glaucoma or those who manifest significant ocular hypertension within hours of the capsulotomy.

• Posterior IOL subluxation or dislocation is rare but may occur, particularly with plate haptic silicone and hydrogel IOLs.

• Chronic endophthalmitis due to release of sequestered organisms into the vitreous is very rare.

Anterior capsular fibrosis and contraction

Since the advent of continuous curvilinear capsulorhexis, contraction of the anterior capsular opening (capsulophimosis) has become a relatively common postoperative complication. It can occur as early as several weeks after surgery and is accompanied by prominent subcapsular fibrosis (Fig. 9.22). The contraction typically progresses for up to three months, and if severe, may require Nd: YAG laser anterior capsulotomy. The severity of contraction is related to the optic material; the highest rate is with plate-haptic silicone IOLs and the lowest with 3-piece acrylic optic-PMMA haptic IOLs. A small capsulorhexis may also predispose to contraction.

Fig. 9.22 Anterior capsular contraction and fibrosis

Miscellaneous postoperative complications

Malposition of IOL

Although uncommon, malposition may be associated with both optical and structural problems. Annoying visual aberrations include glare, haloes, and monocular diplopia if the edge of the IOL becomes displaced into the pupil.

1 Causes

• Primary malposition may occur during surgery due to zonulodialysis, capsular rupture or when one haptic is inserted into the capsular bag and the other into the ciliary sulcus or rarely the angle (Fig. 9.23A).

• Postoperative causes include trauma, eye rubbing and capsular contraction.

2 Treatment. Significant malposition (Fig. 9.23B) may require repositioning or replacement.

Fig. 9.23 (A) Decentred optic with one haptic in the angle and the other in the bag; (B) inferior subluxation of IOL

(Courtesy of P Gili – fig. B)

Cystoid macular oedema

Symptomatic CMO is relatively uncommon following uncomplicated phacoemulsification and in most cases it is mild and transient. It occurs more often after complicated surgery and has a peak incidence at 6–10 weeks, although the interval may be much longer.

1 Risk factors for visually significant CMO include a history of CMO in the other eye, operative complications such as posterior capsular rupture, particularly with vitreous incarceration into the incision site (Fig. 9.24A), AC-IOL (Fig. 9.24B), secondary IOL implantation, prior topical prostaglandin treatment, diabetes and uveitis.

2 Presentation is with blurring of vision, especially for near tasks, and sometimes distortion. Subtle CMO may not be readily visible clinically, but is well demonstrated on OCT (see Ch. 14).

3 Treatment involves correction of the underlying cause, if possible. For example, vitreous incarceration in the anterior segment may be amenable to anterior vitrectomy or YAG laser disruption. As a last resort it may be necessary to remove an AC-IOL. If a correctable cause is not present, treatment can be difficult although many cases resolve spontaneously within a few months. Treatment of persistent CMO involves the following:

a Topical NSAIDs such as ketorolac 0.5% (Acular®) administered q.i.d. may be beneficial even in long-standing cases. Topical treatment may have to continue for an extended period. Intravitreal NSAID injection is a promising new modality.

b Steroids given topically or by posterior periocular injection may be effective.

c Carbonic anhydrase inhibitors given systemically and topically may be beneficial in some cases.

d Intravitreal triamcinolone may be effective in those unresponsive to periocular injections.

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e Intravitreal anti-VEGF agents show some promise for the treatment of pseudophakic CMO but remain under investigation at present.

f Pars plana vitrectomy may be useful for CMO refractory to medical therapy, even in eyes without apparent vitreous disturbance.

Fig. 9.24 Predispositions to cystoid macular oedema. (A) Vitreous incarceration in the incision; (B) anterior chamber IOL

(Courtesy of C Barry – fig. B)

Retinal detachment

Rhegmatogenous retinal detachment, although uncommon following uneventful ECCE or phaco, may be associated with the following risk factors:

1 Preoperative

• Lattice degeneration or retinal breaks should be treated prophylactically prior to cataract surgery or laser capsulotomy if fundus view permits, or as soon as possible thereafter.

• High myopia.

2 Operative

• Disruption of the posterior capsule.

• Vitreous loss, particularly if managed inappropriately, is associated with approximatly a 7% risk of retinal detachment. Myopia of over 6D increases the risk to 15%.

3 Postoperative laser capsulotomy, if performed within a year of cataract surgery.

Congenital cataract

Aetiology

Congenital cataracts occur in about 3 in 10 000 live births. Two-thirds of cases are bilateral and the cause can be identified in about half of those affected. The most common cause is genetic mutation, usually autosomal dominant (AD); other causes include chromosomal abnormalities, metabolic disorders and intrauterine infections. The underlying aetiological factors in unilateral cases remain less clear and the cause can be identified only in approximately 10%. Unilateral cataracts are usually sporadic, without a family history or systemic disease, and affected infants are usually full-term and healthy.

Inheritance

Isolated hereditary cataracts account for about 25% of cases. The mode is most frequently AD but may be autosomal recessive (AR) or X-linked (X-L). The morphology of the opacities and frequently the need for surgery are usually similar in parent and offspring. Isolated inherited congenital cataracts carry a better visual prognosis than those with coexisting ocular and systemic abnormalities.

Morphology

The morphology of congenital cataract is important because it may indicate a likely aetiology, mode of inheritance and effects on vision.

1 Nuclear opacities are confined to the embryonic or foetal nuclei of the lens. The cataract may be dense or composed of fine pulverulent (dust-like) opacities (Fig. 9.25A). They may be associated with microphthalmos.

2 Lamellar opacities affect a particular lamella of the lens both anteriorly and posteriorly (Fig. 9.25B) and in some cases is associated with radial extensions (‘riders’ – Fig. 9.25C). Lamellar opacities may be AD, occur in isolation as well as in infants with metabolic disorders and intrauterine infections.

3 Coronary (supranuclear) cataract lies in the deep cortex and surrounds the nucleus like a crown (Fig. 9.25D). They are usually sporadic and only occasionally hereditary.

4 Blue dot opacities (cataracta punctata caerulea – Fig. 9.25E) are common and innocuous, and may coexist with other types of lens opacity.

5 Sutural in which the opacity follows the anterior or posterior Y suture. It may occur in isolation or in association with other opacities (Fig. 9.25F).

6 Anterior polar cataract may be flat (Fig. 9.26A) or project as a conical opacity into the anterior chamber (pyramidal cataract – Fig. 9.26B). Flat anterior polar opacities are central, less than 3 mm in diameter, bilateral in one-third of cases and visually insignificant. Pyramidal opacities are frequently surrounded by an area of cortical opacity and may affect vision. Occasional associations of anterior polar cataracts include persistent pupillary membrane (Fig. 9.26C), aniridia, Peters anomaly and anterior lenticonus.

7 Posterior polar cataract (Fig. 9.26D) may be occasionally associated with persistent hyaloid remnants (Mittendorf dot), posterior lenticonus and persistent hyperplastic primary vitreous.

8 Central ‘oil droplet’ opacities (Fig. 9.26E) are characteristic of galactosaemia.

9 Membranous cataract is rare and may be associated with Hallermann–Streiff–François syndrome. It occurs when the lenticular material partially or completely reabsorbs leaving behind residual chalky-white lens matter sandwiched between the anterior and posterior capsules (Fig. 9.26F).

Fig. 9.25 Congenital cataracts. (A) Nuclear; (B) lamellar; (C) dense lamellar with ‘riders’; (D) coronary; (E) dense blue dot; (F) sutural and fine blue dot

(Courtesy of R Bates – fig. E)

Fig. 9.26 Congenital cataracts. (A) Flat anterior polar; (B) pyramidal anterior polar; (C) anterior polar with persistent pupillary membrane; (D) posterior polar associated with Mittendorf dot; (E) ‘oil droplet’; (F) membranous

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. D; K Nischal – fig. E)

Systemic metabolic associations

Many systemic paediatric conditions may be associated with congenital cataract. The vast majority are extremely rare and of interest only to paediatric ophthalmologists. The general ophthalmologist should, however, be aware of the following conditions:

Galactoasemia

1 Pathogenesis. Galactosaemia is an AR condition characterized by severe impairment of galactose utilization caused by absence of the enzyme galactose-1-phosphate uridyl transferase (GPUT).

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2 Systemic features, which become manifest during infancy, include failure to thrive, lethargy, vomiting and diarrhoea. ‘Reducing substance’ is found in the urine after drinking milk. Unless galactose, in the form of milk and milk products, is withheld from the diet, hepatosplenomegaly, renal disease, anaemia, deafness and mental handicap occur subsequently with early death.

3 Ocular features. Cataract, characterized by a central ‘oil droplet’ opacity (see Fig. 9.26E), develops within the first few days or weeks of life in a large percentage of patients. The exclusion of galactose (in milk products) from the diet will prevent the progression of cataract and may reverse early lens changes.

Lowe syndrome

1 Pathogenesis. Lowe syndrome is an X-L inborn error of amino acid metabolism.

2 Systemic features include psychomotor retardation, Fanconi syndrome of the proximal renal tubules, muscular hypotonia, frontal prominence, chubby cheeks and sunken eyes (Fig. 9.27A). It is one of the few conditions in which congenital cataract and congenital glaucoma may coexist.

3 Ocular features

• Cataract, which may be capsular, lamellar, nuclear or total, is universal. The lens is also small, thin and disc-like (microphakia) and may show posterior lentiglobus. Female carriers manifest micropunctate cortical lens opacities, usually without visual impact.

• Congenital glaucoma is present in 60% of cases.

• Other occasional findings include miosis and poor pupillary dilation, and posterior lenticonus.

Fig. 9.27 Some syndromic associations of congenital cataract. (A) Lowe syndrome; (B) Down syndrome; (C) Hallermann–Streiff–François syndrome

(Courtesy of N Rogers – fig. C)

Fabry’ disease

1 Pathogenesis. Fabry disease is an X-L lysosomal storage disorder caused by deficiency of α-galactosidase A.

2 Systemic features include periodic burning pain in the extremities, purple cutaneous telangiectasis (angiokeratoma corporis diffusum, see Fig. 6.67A), hypertrophic cardiomyopathy and renal disease.

3 Ocular features

• Cataracts may consist of subtle minute dots along the suture lines or granular white subcapsular wedge-shaped opacities with the base at the equator.

• Other findings include vortex keratopathy (see Fig. 6.67B), conjunctival vascular tortuosity (see Fig. 6.67C) and retinal vascular tortuosity (especially venous).

Mannosidosis

1 Pathogenesis. Mannosidosis is an AR disorder with deficiency of α-mannosidase and consequent excretion of mannose-containing oligosaccharides in the urine.

2 Systemic features. There are two types:

a Infantile, which is characterized by early rapidly progressive mental deterioration, hepatosplenomegaly and bony deformities.

b Juvenile-adult in which mental deterioration does not occur until late childhood. Patients also manifest facial anomalies, deafness, muscular weakness and spinal abnormalities.

3 Ocular features

• Punctate lens opacities arranged in a spoke-like pattern in the posterior lens cortex are common.

• Corneal clouding is less common.

Other metabolic disorders

These include hypoparathyroidism, pseudohypopara-thyroidism, hypoglycaemia and hyperglycaemia.

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Associated intrauterine infections

Congenital rubella

1 Pathogenesis. Congenital rubella (German measles) results from transplacental transmission of virus to the fetus from an infected mother, usually during the first trimester of pregnancy that may lead to serious chronic fetal infection and malformations. The risk to the fetus is closely related to the stage of gestation at the time of maternal infection. Fetal infection is about 50% during the first 8 weeks, 33% between weeks 9 and 12, and about 10% between weeks 13 and 24.

2 Systemic features include spontaneous abortion, stillbirth, congenital heart malformations, deafness, microcephaly, mental handicap, hypotonia, hepatosplenomegaly, thrombocytopenic purpura, pneumonitis, myocarditis and metaphyseal bone lesions.

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3 Ocular features

• Cataract occurs in about 15% of cases. After the gestational age of 6 weeks, the virus is incapable of crossing the lens capsule so that the lens is immune. Although the lens opacities (which may be unilateral or bilateral) are usually present at birth, they may occasionally develop several weeks or even months later. The opacity may involve the nucleus, with a dense pearly appearance or may present as a more diffuse opacity involving most of the lens. The virus is capable of persisting within the lens for up to 3 years after birth.

• Other ocular manifestations include microphthalmos, glaucoma, retinopathy, keratitis, anterior uveitis and iris atrophy, extreme refractive errors, pendular nystagmus and strabismus secondary to poor vision. Almost all microphthalmic eyes have cataracts and almost all cataractous microphthalmic eyes have glaucoma.

Toxoplasmosis

1 Systemic features include seizures, hydrocephalus, microcephaly, hepatosplenomegaly, deafness and intracranial calcification.

2 Ocular features apart from cataract include chorioretinitis, microphthalmos and optic atrophy.

Cytomegalovirus infection

1 Systemic features include jaundice, hepatosplenomegaly, microcephaly and intracranial calcification.

2 Ocular features apart from cataract include chorioretinitis, microphthalmos, keratitis and optic atrophy.

Varicella

1 Systemic features include mental handicap, cortical cerebral atrophy, cutaneous scarring and limb deformities; death in early infancy is common.

2 Ocular features apart from cataract include microphthalmos, Horner syndrome, chorioretinitis, optic disc hypoplasia and optic atrophy.

Associated chromosomal abnormalities

Down syndrome (trisomy 21)

1 Systemic features include mental handicap, stunted growth, upward-slanting palpebral fissures, epicanthic folds, flat midface with relative prognathism (Fig. 9.27B), brachycephalic skull with flattening of the occiput, broad short hands with a single transverse palmar (simian) crease, protruding tongue, small ears, excess skin on the back of the neck, thyroid dysfunction, cardiorespiratory disease (particularly Fallot tetralogy) and reduced life span.

2 Ocular features

• Cataract of various morphology occur in about 75% of patients. The opacities are usually symmetrical and often develop in late childhood.

• Other features include iris Brushfield spots and hypoplasia, chronic blepharitis, myopia, strabismus, keratoconus and anomalous optic disc vasculature.

Edwards syndrome (trisomy 18)

1 Systemic features include micrognathia, webbed neck, short digits and clenched hands, low-set ears, deafness, cardiac anomalies, mental handicap and very early demise.

2 Ocular features apart from cataract include ptosis, microphthalmos, corneal opacity, uveal and disc coloboma and vitreoretinal dysplasia.

Cri du chat syndrome (partial deletion of 5p)

1 Systemic features include microcephaly, growth retardation, low-set ears, cat-like cry and mental handicap.

2 Ocular features apart from cataract include hypertelorism, down-sloping palpebral fissures and strabismus.

Associated skeletal syndromes

Hallermann–Streiff–François syndrome

1 Systemic features of this sporadic condition include frontal prominence, small beaked nose, baldness (Fig. 9.27C), progeria, micrognathia and pointed chin, short stature, hypodontia and a narrow upper respiratory airway.

2 Ocular features

• Cataract, which may be membranous (see Fig. 9.26F), occurs in 90% of cases.

• Other features include blue sclera, bilateral microphthalmos, disc coloboma, nystagmus and strabismus.

Nance–Horan syndrome

1 Systemic features of this X-L condition include supernumerary incisors, prominent ears, anteverted pinnae and shortened metacarpals.

2 Ocular features. Cataract may be dense and associated with mild microphthalmos. Female carriers may show a prominent Y suture or have Y suture opacities (see Fig. 9.25F).

Management

Ocular examination

Since a formal estimate of visual acuity cannot be obtained in the neonate, reliance is required on the density and morphology of the opacity, associated ocular findings and the visual behaviour of the child in order to assess the visual significance of the opacity. It is also important to examine parents and siblings.

1 Density and potential impact on visual function is assessed on the basis of appearance of the red reflex and the quality of the fundus view on direct and indirect ophthalmoscopy; examination of the neonate has been made easier with the introduction of high quality portable slit-lamps. On ophthalmoscopy cataract density is graded as follows:

• A very dense cataract occluding the pupil will preclude any view of the fundus and the decision to operate is straightforward.

• A less dense cataract, although still visually significant, will allow visualization of the retinal vasculature with the indirect but not with the direct ophthalmoscope. Other features of visually significant cataract are central or posterior opacities over 3 mm in diameter.

• A visually insignificant opacity will allow clear visualization of the retinal vasculature with both the indirect and direct ophthalmoscope. Other features of visually insignificant cataract are central opacities less than 3 mm in diameter and peripheral, anterior or punctate opacities with intervening clear zones.

2 Morphology of the opacity can give important clues to aetiology (see above).

3 Associated ocular pathology may involve the anterior segment (corneal clouding, microphthalmos, glaucoma, persistent fetal vasculature) or the posterior segment (chorioretinitis, Leber amaurosis, rubella retinopathy, foveal or optic nerve hypoplasia).

4 Other indicators of severe visual impairment include absence of central fixation, nystagmus and strabismus.

5 Special tests such as forced choice preferential looking and visually evoked potentials also provide helpful information but should not be relied exclusively upon since they may be misleading.

Systemic investigations

Unless there is an established hereditary basis for the cataracts, the investigation of the infant with bilateral cataracts should include the following:

1 Serology for intrauterine infections.

2 Urine. Urinalysis for reducing substance after drinking milk (galactosaemia) and chromatography for amino acids (Lowe syndrome).

3 Other investigations include fasting blood glucose, serum calcium and phosphorus, red blood cell GPUT and galactokinase levels. Children who have calcium and phosphorus anomalies severe enough to cause cataracts are unwell.

4 Referral to a paediatrician may be warranted for dysmorphic features or suspicion of other systemic diseases. Chromosome analysis may be useful in this context.

Treatment

Timing is crucial and the main considerations are as follows:

1 Bilateral dense cataracts require early surgery when the child is 4–6 weeks of age to prevent the development of stimulus deprivation amblyopia. If the severity is asymmetrical, the eye with the denser cataract should be addressed first.

2 Bilateral partial cataracts may not require surgery until later if at all. In cases of doubt it may be prudent to defer surgery, monitor lens opacities and visual function and intervene later if vision deteriorates.

3 Unilateral dense cataract merits urgent surgery (possibly within days) followed by aggressive anti-amblyopia therapy, despite which the results are often poor. The timing of intervention should be balanced by the suggestion that early intervention (<4 weeks) may result in an increased risk of subsequent secondary glaucoma. If the cataract is detected after 16 weeks of age then the visual prognosis is particularly poor.

4 Partial unilateral cataract can usually be observed or treated non-surgically with pupillary dilatation and possibly part time contralateral occlusion to prevent amblyopia.

5 Surgery involves anterior capsulorhexis, aspiration of lens matter, capsulorhexis of the posterior capsule, limited anterior vitrectomy and IOL implantation, if appropriate. It is important to correct associated refractive errors.

Postoperative complications

Cataract surgery in children carries a higher incidence of complications than in adults.

1 Posterior capsular opacification is nearly universal if the posterior capsule is retained in a child under the age of 6 years. It is also of more significance in young children because of its amblyogenic effect. The incidence of opacification is reduced when posterior capsulorhexis is combined with vitrectomy.

2 Secondary membranes may form across the pupil, particularly in microphthalmic eyes or those with associated chronic uveitis. A fibrinous postoperative uveitis in an otherwise normal eye, unless vigorously treated, may also result in membrane formation.

3 Proliferation of lens epithelium is universal but usually visually inconsequential, since it does not involve the visual axis. It becomes encapsulated within the remnants of the anterior and posterior capsules and is referred to as a Soemmerring ring.

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4 Glaucoma eventually develops in about 20% of eyes.

• Closed-angle glaucoma may occur in the immediate postoperative period in microphthalmic eyes secondary to pupillary block.

• Secondary open-angle glaucoma may develop years after the initial surgery; it is therefore important to monitor the intraocular pressure long-term.

5 Retinal detachment is an uncommon and usually late complication.

Visual rehabilitation

Although the technical difficulties of performing cataract surgery in infants and young children have mostly been resolved, visual results are hampered by amblyopia. With regard to optical correction for the aphakic child, the two main considerations are age and laterality of aphakia.

1 Spectacles are useful for older children with bilateral aphakia.

2 Contact lenses provide a superior optical solution for both unilateral and bilateral aphakia. Tolerance is usually reasonable until the age of about 2 years, although after this period problems with compliance may develop as the child becomes more active and independent.

3 IOL implantation is increasingly being performed in younger children and appears to be effective and safe in selected cases. Awareness of the rate of myopic shift which occurs in the developing eye, combined with accurate biometry, allows the calculation of an IOL power targeted at initial hypermetropia (correctable with spectacles) which will ideally decay towards emmetropia later in life. However, final refraction is variable and emmetropia in adulthood cannot be guaranteed.

4 Occlusion to treat or prevent amblyopia is essential. Atropine penalization may also be considered.

Ectopia lentis

Ectopia lentis refers to a displacement of the lens from its normal position. The lens may be completely dislocated, rendering the pupil aphakic (luxated), or partially displaced, still remaining in the pupillary area (subluxated). Ectopia lentis may be hereditary or acquired. Acquired causes include trauma, a large eye (e.g. high myopia, buphthalmos), anterior uveal tumours and hypermature cataract. Only hereditary causes are discussed below.

Without systemic associations

1 Familial ectopia lentis is an AD condition characterized by bilateral symmetrical superotemporal displacement. It may manifest congenitally or later in life.

2 Ectopia lentis et pupillae is a rare, congenital, bilateral, AR disorder characterized by displacement of the pupil and the lens in opposite directions. The pupils are small, slit-like and dilate poorly (Fig. 9.28A). Other findings include iris transillumination, large corneal diameter, glaucoma, cataract and microspherophakia.

3 Aniridia is occasionally associated with ectopia lentis (Fig. 9.28B).

Fig. 9.28 Ectopia lentis without systemic associations. (A) Ectopia lentis et pupillae; (B) inferior subluxation in aniridia

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. A; U Raina –fig.B)

With systemic associations

Marfan syndrome

1 Pathogenesis. There is mutation of the fibrillin-1 gene (FBN1) on chromosome 15q21.

2 Inheritance is AD with variable expressivity; a minority of patients manifest only ocular signs.

3 Musculoskeletal features

• Tall, thin stature with disproportionately long limbs compared with the trunk (arm span > height – Fig. 9.29A).

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• Kyphoscoliosis, sternal prominence (pectus carinatum) or depression (pectus excavatum).

• Long spider-like fingers and toes (arachnodactyly – Fig. 9.29B) and mild joint laxity.

• A narrow high-arched (‘gothic’) palate (Fig. 9.29C).

• A long-shaped head, malar hypoplasia, enophthalmos and downslanting palpebral fissures.

• Flat feet, cutaneous striae and easy bruising.

• Muscular underdevelopment and predisposition to hernias.

4 Cardiovascular lesions include dilatation of the aortic root, mitral valve prolapse and aortic aneurysm formation.

5 Ectopia lentis which is bilateral and symmetrical is present in 80% of cases. Subluxation is most frequently supero-temporal, but may be in any meridian. Because the zonule is frequently intact (Fig. 9.29D), accommodation is retained, although rarely the lens may dislocate into the anterior chamber or vitreous (Fig. 9.29E). The lens may also be microspherophakic.

6 Other ocular features include angle anomaly which may result in glaucoma, retinal detachment associated with lattice degeneration, hypoplasia of the dilator pupillae, peripheral iris transillumination defects, cornea plana and strabismus.

Fig. 9.29 Marfan syndrome. (A) Long limbs compared with the trunk; (B) arachnodactyly; (C) high-arched palate; (D) superotemporal subluxation with intact zonule; (E) dislocation into the vitreous is rare

Weill–Marchesani syndrome

Weill–Marchesani syndrome is a rare systemic connective tissue disease, conceptually the converse of Marfan syndrome.

1 Inheritance is AR or AD; the former maps to 19p13.3-p13.2 and the latter to FBN1, the same as Marfan syndrome.

2 Systemic features include short stature, brachydactyly characterized by short, stubby fingers (Fig. 9.30A) and toes, stiff joints and mental handicap.

3 Ectopia lentis which is inferior occurs in 50% of cases during late childhood or early adult life. Microspherophakia is common so that subluxation occurs anteriorly to cause pupil block or occasionally into the anterior chamber (Fig. 9.30B).

4 Other ocular features include angle anomalies, asymmetrical axial lengths and presenile vitreous liquefaction.

Fig. 9.30 Weill–Marchesani syndrome. (A) Bradydactyly; (B) dislocation of microspheric lens into the anterior chamber

(Courtesy of R Curtis – fig. B)

Homocystinuria

1 Pathogenesis. Inborn error of metabolism in which decreased hepatic activity of cystathionine beta-synthase results in systemic accumulation of homocysteine and methionine.

2 Inheritance is AR with the gene locus on chromosome 21q.22.3.

3 Systemic features

• Coarse blond hair, blue irides, malar flush (Fig. 9.31A), Marfanoid habitus but infrequent arachnodactyly.

• Neurodevelopmental delay, mental handicap, psychiatric disturbance and osteoporosis.

• Thromboses in any vessel and at any age, particularly postoperatively or postpartum.

• Treatment involves oral pyridoxine, folic acid and vitamin B12 to reduce plasma homocysteine and methionine levels.

4 Ectopia lentis, typically inferonasal (Fig. 9.31B), is almost universal by the age of 25 years in untreated cases. The zonule, which normally contains high levels of cysteine (deficient in homocystinuria), disintegrates (Fig. 9.31C) so that accommodation is often lost. Secondary angle-closure may occur as a result of pupil block caused by lens incarceration in the pupil, or a total dislocation into the anterior chamber.

5 Other ocular features include iris atrophy, optic atrophy, cataract, corneal opacity, myopia and retinal detachment.

Fig. 9.31 Homocystinuria. (A) Coarse blond hair; (B) inferior subluxation with zonular disintegration; (C) histology shows matted zonular fibres lying over the ciliary epithelium

(Courtesy of J Schuman, V Christopoulos, D Dhaliwal, M Kahook and R Noecker, from Lens and Glaucoma, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. B; J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. C)

Other systemic associations

1 Sulphite oxidase deficiency is an AR inborn error of sulphur metabolism characterized by progressive psychomotor deterioration, progressive muscular rigidity, decerebrate posture and demise usually before the age of 5 years. Ectopia lentis is universal.

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2 Hyperlysinaemia is a very rare, AR inborn error of metabolism caused by a deficiency in lysine alpha-ketoglutarate reductase. Systemic features include lax ligaments, hypotonic muscles, seizures and mental handicap. It is occasionally associated with ectopia lentis.

3 Stickler syndrome is occasionally associated with ectopia lentis, retinal detachment being the most common problem.

4 Ehlers–Danlos syndrome is occasionally associated with ectopia lentis, scleral fragility, keratoconus and myopia being more common.

Management

The main complications of ectopia lentis are (a) refractive error (lenticular myopia), (b) optical distortion due to astigmatism and/or lens edge effect, (c) glaucoma (see Ch. 10) and, rarely, (d) lens-induced uveitis.

1 Spectacle correction may correct astigmatism induced by lens tilt or edge effect in eyes with mild subluxation. Aphakic correction may also afford good visual results if a significant portion of the visual axis is aphakic in the undilated state.

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2 Surgical removal of the lens, using closed intraocular microsurgical techniques, is indicated for intractable ametropia, meridional amblyopia, cataract, lens-induced glaucoma, uveitis or endothelial touch.

Abnormalities of shape

Anterior lenticonus

1 Signs

• Bilateral axial projection of the anterior surface of the lens into the anterior chamber (Fig. 9.32A).

• In early cases the red reflex shows an ‘oil-droplet’ (Fig. 9.32B).

2 Alport syndrome is present in the vast majority of patients. It is an AD or X-LR condition characterized by progressive sensorineural deafness and renal disease associated with abnormal glomerular basement membrane. Haematuria usually begins in childhood, whereas renal failure occurs later.

3 Other ocular features include fleck retinopathy (see Fig. 15.17) and posterior polymorphous corneal dystrophy (see Fig. 6.59).

Fig. 9.32 (A) Anterior lenticonus; (B) red reflex shows an ‘oil-droplet’ sign

Posterior lenticonus

1 Inheritance. Most cases are unilateral, sporadic and not associated with systemic abnormalities. Rarely bilateral cases may be familial.

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2 Signs

• A round or conical bulge of the posterior axial zone of the lens into the vitreous (Fig. 9.33A) associated with local thinning or absence of the capsule.

• Opacification of the posterior capsule (Fig. 9.33B) is common.

• With age, the bulge progressively increases in size and the lens cortex may opacify. Progression of cataract is variable, but many cases present with an acutely opacified white lens in infancy or early childhood.

Fig. 9.33 (A) Posterior lenticonus; (B) red reflex shows opacification of the posterior capsule

Lentiglobus

Lentiglobus is a very rare, usually unilateral, generalized hemispherical deformity of the lens which may be associated with posterior polar lens opacity.

Microspherophakia

1 Signs. The lens is small and spherical (Fig. 9.34).

2 Causes include familial (dominant) microspherophakia which is not associated with systemic defects, Marfan syndrome, Weill–Marchesani syndrome, hyperlysinaemia and congenital rubella.

3 Ocular associations include Peters anomaly and familial ectopia lentis et pupillae.

4 Complications include lenticular myopia, subluxation and total dislocation into the anterior chamber (see Fig. 9.30B).

Fig. 9.34 Microspherophakia

(Courtesy of R Bates)

Microphakia

1 Sign. A lens with a smaller than normal diameter (Fig. 9.35).

2 Association. Lowe syndrome (see above), in which the lens is not only small but also disc-like.

Fig. 9.35 Microphakia

Coloboma

A coloboma is characterized by notching (segmental agenesis) at the inferior equator (Fig. 9.36) with corresponding absence of zonular fibres. It is not a true coloboma as there is no focal absence of a tissue layer due to failure of closure of the optic fissure. Occasionally a lens coloboma may be associated with a coloboma of the iris or fundus.

Fig. 9.36 Lens coloboma

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