Anatomy

The orbit is a pear-shaped cavity, the stalk of which is the optic canal (Fig. 3.1). The intraorbital portion of the optic nerve is longer (25 mm) than the distance between the back of the globe and the optic canal (18 mm). This allows for significant forward displacement of the globe (proptosis) without excessive stretching of the nerve.

Fig. 3.1 Anatomy of the orbit

Clinical signs

Soft tissue involvement

1 Signs include lid and periorbital oedema, skin discoloration, ptosis, chemosis (oedema of the conjunctiva and caruncle) and epibulbar injection (Fig. 3.2A).

2 Causes include thyroid eye disease, orbital inflammatory diseases and obstruction to venous drainage.

Fig. 3.2 General signs of orbital disease. (A) Soft tissue involvement; (B) left proptosis; (C) right inferior dystopia; (D) right ophthalmoplegia of elevation

Proptosis

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Proptosis describes an abnormal protrusion of the globe which may be caused by retrobulbar lesions or, less frequently, a shallow orbit. Asymmetrical proptosis is best detected by looking down at the patient from above and behind (Fig. 3.2B). The following characteristics are relevant.

1 Direction of proptosis may indicate the possible pathology. For example, space-occupying lesions within the muscle cone, such as cavernous haemangiomas and optic nerve tumours cause axial proptosis, whereas extraconal lesions usually give rise to eccentric proptosis, the direction of which is governed by the site of the mass.

2 Severity of proptosis can be measured with a plastic rule resting on the lateral orbital margin (Fig. 3.3A) or an exophthalmometer, by means of which the corneal apices are visualized in mirrors and the degree of ocular protrusion is read off a scale (Fig. 3.3B). Measurements can be taken both relaxed and with the Valsalva manoeuvre. Readings greater than 20 mm are indicative of proptosis and a difference of 2 mm between the two eyes is suspicious regardless of the absolute value. Proptosis is graded as mild (21–23 mm), moderate (24–27 mm) and severe (28 mm or more). The dimensions of the palpebral apertures and any lagophthalmos should also be noted.

3 Pseudoproptosis (false impression of proptosis) may be due to facial asymmetry, severe ipsilateral enlargement of the globe (e.g. high myopia or buphthalmos), ipsilateral lid retraction or contralateral enophthalmos.

Fig. 3.3 Measurement of proptosis. (A) With a plastic rule; (B) with an exophthalmometer

Fundus changes

1 Optic disc swelling may be the initial feature of compressive optic neuropathy (Fig. 3.4A).

2 Optic atrophy (Fig. 3.4B), which may be preceded by swelling, is a feature of severe compressive optic neuropathy. Important causes include thyroid eye disease and optic nerve tumours.

3 Opticociliary collaterals consist of enlarged pre-existing peripapillary capillaries which divert blood from the central retinal venous circulation to the peripapillary choroidal circulation when there is obstruction of the normal drainage channels. On ophthalmoscopy the vessels appear as large tortuous channels most frequently on the temporal side which disappear at the disc margin (Fig. 3.4C). The collaterals may be associated with any orbital or optic nerve tumours which compress the intraorbital optic nerve and impair blood flow through the central retinal vein. The most common tumour associated with shunts is the optic nerve sheath meningioma but they may also occur with optic nerve glioma, central retinal vein occlusion, idiopathic intracranial hypertension and glaucoma.

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4 Choroidal folds are a series of roughly parallel alternating light and dark delicate lines or striae which are most frequently noted at the posterior pole (Fig. 3.4D). Choroidal folds may occur in a wide variety of orbital lesions including tumours, thyroid eye disease, inflammatory conditions and mucoceles. The folds are usually asymptomatic and do not cause visual loss. Although choroidal folds tend to be more common with greater amounts of proptosis and anteriorly located tumours, in some cases their presence can precede the onset of proptosis.

Fig. 3.4 Fundus changes in orbital disease. (A) Disc swelling; (B) optic atrophy; (C) opticociliary vessels; (D) choroidal folds

(Courtesy of J Donald M Gass, from Stereoscopic Atlas of Macular Diseases, Mosby 1997 – fig. D)

Special investigations

Introduction

Thyrotoxicosis

Thyrotoxicosis (hyperthyroidism) is a condition involving excessive secretion of thyroid hormones. Graves disease, the most common subtype of hyperthyroidism, is an autoimmune disorder in which IgG antibodies bind to thyroid stimulating hormone (TSH) receptors in the thyroid gland and stimulate secretion of thyroid hormones. It is more common in females and may be associated with other autoimmune disorders.

1 Presentation is in the 3–4th decades with weight loss despite good appetite, increased bowel frequency, sweating, heat intolerance, nervousness, irritability, palpitations, weakness and fatigue.

2 Signs

a External

• Diffuse thyroid enlargement (Fig. 3.5A), fine hand tremor, palmar erythema, and warm and sweaty skin.

• Finger clubbing (thyroid acropachy – Fig. 3.5B) and onycholysis (Plummer nails).

• Pretibial myxoedema is an infiltrative dermopathy characterized by raised plaques on the anterior aspect of the legs, extending on to the dorsum of the foot (Fig. 3.5C).

• Alopecia and vitiligo (Fig. 3.5D).

• Myopathic proximal muscle weakness but brisk tendon reflexes.

b Cardiovascular

• Sinus tachycardia, atrial fibrillation and premature ventricular beats.

• High output heart failure.

3 Investigations. Thyroid function tests include serum T3, T4, TSH, thyroxine binding globulin (TBG) and thyroid-stimulating immunoglobulin (TSI).

4 Treatment options include carbimazole, propylthiouracil, propranolol, radioactive iodine and partial thyroidectomy.

Fig. 3.5 Systemic signs in thyrotoxicosis. (A) Goitre; (B) acropachy; (C) very severe pretibial myxoedema; (D) vitiligo

(Courtesy of M Zatouroff, from Physical Signs in General Medicine, Mosby-Wolfe 1996 – fig. C)

Pathogenesis of ophthalmopathy

Thyroid ophthalmopathy involves an organ-specific autoimmune reaction in which a humoral agent (IgG antibody) produces the following changes:

1 Inflammation of extraocular muscles characterized by pleomorphic cellular infiltration (Fig. 3.6), associated with increased secretion of glycosaminoglycans and osmotic imbibition of water. The muscles become enlarged, sometimes up to eight times their normal size, and may compress the optic nerve. Subsequent degeneration of muscle fibres eventually leads to fibrosis, which exerts a tethering effect on the involved muscle, resulting in restrictive myopathy and diplopia.

2 Inflammatory cellular infiltration with lymphocytes, plasma cells, macrophages and mast cells of interstitial tissues, orbital fat and lacrimal glands with accumulation of glycosaminoglycans and retention of fluid. This causes an increase in the volume of orbital contents and secondary elevation of intraorbital pressure, which may itself cause further fluid retention within the orbit.

Fig. 3.6 Cellular infiltration of an extraocular muscle in thyroid eye disease

Soft tissue involvement

Fig. 3.7 Soft tissue involvement in thyroid eye disease. (A) Epibulbar hyperaemia overlying a horizontal rectus muscle; (B) periorbital oedema, chemosis and prolapse of fat into the eyelids; (C) superior limbic keratoconjunctivitis

Lid retraction

Signs

The upper lid margin normally rests 2 mm below the limbus (Fig. 3.8A, right eye). Lid retraction is suspected when the margin is either level with or above the superior limbus, allowing sclera to be visible (’scleral show’; Fig. 3.8A, left eye). Likewise, the lower eyelid normally rests at the inferior limbus; retraction is suspected when sclera shows below the limbus. Lid retraction may occur in isolation or in association with proptosis which exaggerates its severity.

1 Dalrymple sign is lid retraction in primary gaze (Fig. 3.8B).

2 Kocher sign describes a staring and frightened appearance of the eyes which is particularly marked on attentive fixation (Fig. 3.8C).

3 Von Graefe sign signifies retarded descent of the upper lid on downgaze (lid lag – Fig. 3.8D).

Fig. 3.8 Lid signs in thyroid eye disease. (A) Mild left lid retraction; (B) moderate bilateral symmetrical lid retraction; (C) severe bilateral lid retraction; (D) right lid lag on downgaze

(Courtesy of G Rose – fig. B)

Proptosis

Signs

Proptosis is axial, unilateral or bilateral, symmetrical (Fig. 3.9A) or asymmetrical (Fig. 3.9B), and frequently permanent. Severe proptosis may compromise lid closure with resultant exposure keratopathy, corneal ulceration and infection (Fig. 3.9C).

Fig. 3.9 Proptosis in thyroid eye disease. (A) Symmetrical; (B) asymmetrical; (C) bacterial keratitis due to exposure

(Courtesy of A Pearson figs A and B; S Kumar Puri – fig. C)

Management

Management is controversial. Some favour early surgical decompression whereas others consider surgery only when non-invasive methods have failed or are inappropriate.

1 Systemic steroids may be used in rapidly progressive and painful proptosis during the congestive phase, unless contraindicated (e.g. tuberculosis or peptic ulceration).

a Oral prednisolone 60–80 mg/day is given initially. Reduction in discomfort, chemosis and periorbital oedema usually occurs within 48 hours, at which point, the dose should be tapered. Maximal response is usually achieved within 2–8 weeks. Ideally steroid therapy should be discontinued after about 3 months, although long-term low-dose maintenance may be necessary.

b Intravenous methylprednisolone (e.g. 0.5 g in 200–500 mL isotonic saline given over 30 minutes), which may be repeated after 48 hours, is usually reserved for acute compressive optic neuropathy, because of potential cardiovascular risks which mandate careful supervision by a physician.

2 Radiotherapy may be used in addition to steroids or when steroids are contraindicated or ineffective. A positive response is usually evident within 6 weeks, with maximal improvement by 4 months.

3 Combined therapy with irradiation, azathioprine and low-dose prednisolone may be more effective than steroids or radiotherapy alone. Monoclonal antibody treatment with rituximab also shows very good results.

4 Surgical decompression may be considered either as the primary treatment or when non-invasive methods are ineffective, such as for cosmetically unacceptable proptosis in the quiescent phase. Decompression aims to increase the volume of the orbit by removing the bony walls and may be combined with removal of orbital fat to increase the retroplacement of the globe.

• One-wall (deep lateral) decompression (Fig. 3.10) is effective (approximately 4–5 mm reduction in proptosis) and may reduce the risk of postoperative diplopia.

• Two-wall (balanced medial and lateral) decompression provides a greater effect but with a significant risk of inducing diplopia.

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• Three-wall decompression includes the floor with a reduction in proptosis of 6–10 mm but may lead to hypoglobus and has a higher risk of infraorbital nerve damage and diplopia.

• Very severe proptosis may require additional removal of part of the orbital roof (four-wall decompression).

• Most surgery is undertaken via an external approach though the medial wall and the medial part of the floor can be reached endoscopically.

Fig. 3.10 Axial CT following bilateral, lateral and medial wall decompression

(Courtesy of A Pearson)

Restrictive myopathy

Diagnosis

Between 30% and 50% of patients with TED develop ophthalmoplegia and this may be permanent. Ocular motility is restricted initially by inflammatory oedema and later by fibrosis. Intraocular pressure may increase in upgaze due to ocular compression by a fibrotic inferior rectus. In order of frequency the four ocular motility defects are:

1 Elevation defect (Fig. 3.11A) caused by fibrotic contracture of the inferior rectus, which may mimic superior rectus palsy.

2 Abduction defect due to fibrosis of the medial rectus, which may simulate 6th nerve palsy.

3 Depression defect (Fig. 3.11B) secondary to fibrosis of the superior rectus.

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4 Adduction defect caused by fibrosis of the lateral rectus.

Fig. 3.11 Restrictive thyroid myopathy. (A) Defective elevation of the left eye; (B) defective depression of the right eye

Optic neuropathy

Optic neuropathy is an uncommon but serious complication caused by compression of the optic nerve or its blood supply at the orbital apex by the congested and enlarged recti (Fig. 3.12). Such compression, which may occur in the absence of significant proptosis, may lead to severe but preventable visual impairment.

Fig. 3.12 CT shows muscle enlargement in thyroid eye disease. (A) Axial view; (B) coronal view – note sparing of the right lateral rectus muscle; (C) coronal view shows crowding at the orbital apex

(Courtesy of N Sibtain – figs A and B; J Nerad, K Carter and M Alford, from Oculoplastic and Reconstructive Surgery, in Rapid Diagnosis in Ophthalmology, Mosby 2008 – fig. C)

Preseptal cellulitis

Preseptal cellulitis is an infection of the subcutaneous tissues anterior to the orbital septum. Although not strictly an orbital disease, it is included here because it must be differentiated from the much less common but potentially more serious orbital cellulitis. Occasionally rapid progression to orbital cellulitis may occur.

Fig. 3.13 (A) Left preseptal cellulitis; (B) axial CT shows opacification anterior to the orbital septum

Bacterial orbital cellulitis

Bacterial orbital cellulitis is a life-threatening infection of the soft tissues behind the orbital septum. It can occur at any age but is more common in children. The most common causative organisms are S. pneumoniae, S. aureus, S. pyogenes and H. influenzae.

Diagnosis

1 Presentation is with the rapid onset of severe malaise, fever, pain and visual impairment.

2 Signs

• Unilateral tender warm and red periorbital and lid oedema.

• Proptosis, often obscured by lid swelling, is most frequently lateral and downwards.

• Painful ophthalmoplegia (Fig. 3.14A).

• Optic nerve dysfunction.

3 CT shows opacification posterior to the orbital septum (Fig. 3.14B).

Fig. 3.14 (A) Right orbital cellulitis with ophthalmoplegia; (B) axial CT shows preseptal and orbital opacification

Rhino-orbital mucormycosis

Mucormycosis is a very rare opportunistic infection caused by fungi of the family Mucoraceae, which typically affects patients with diabetic ketoacidosis or immunosuppression. This aggressive and often fatal infection is acquired by the inhalation of spores, which give rise to an upper respiratory infection. The infection then spreads to the contiguous sinuses and subsequently to the orbit and brain. Invasion of blood vessels by the hyphae results in occlusive vasculitis with ischaemic infarction of orbital tissues.

Fig. 3.15 Necrosis of the eyelid in rhino-orbital mucormycosis

Idiopathic orbital inflammatory disease

Idiopathic orbital inflammatory disease (IOID), previously referred to as orbital pseudotumour, is an uncommon disorder characterized by non-neoplastic, non-infective, space-occupying orbital lesions. The inflammatory process may involve any or all of the orbital soft tissues, resulting in, for example, myositis, dacryoadenitis, optic perineuritis or scleritis. Histopathological analysis reveals pleomorphic inflammatory cellular infiltration followed by reactive fibrosis, but has thus far shown no correlation between clinicopathological features and the subsequent course of the disease. Unilateral disease is the rule in adults, although in children bilateral involvement may occur. Simultaneous orbital and sinus involvement is a rare distinct entity.

Diagnosis

1 Presentation is with acute periorbital redness, swelling and pain (Fig. 3.16A).

2 Signs

• Congestive proptosis and ophthalmoplegia may occur.

• Optic nerve dysfunction, particularly if the inflammation involves the posterior orbit.

3 CT shows ill-defined orbital opacification and loss of definition of contents (Fig. 3.16B and C).

4 Course. This follows one of the following patterns:

• Spontaneous remission after a few weeks without sequelae.

• Intermittent episodes of activity with eventual remission.

• Severe prolonged inflammation eventually leading to progressive fibrosis of orbital tissues, resulting in a ‘frozen orbit’ characterized by ophthalmoplegia, which may be associated with ptosis and visual impairment caused by optic nerve involvement.

Fig. 3.16 (A) Left idiopathic orbital inflammatory disease. (B) CT axial view shows ill-defined orbital opacification; (C) coronal view

(Courtesy of R Bates – fig. A; A Pearson – figs B and C)

Orbital myositis

Orbital myositis is an idiopathic, non-specific inflammation of one or more extraocular muscles and is considered a subtype of IOID.

Fig. 3.17 Orbital myositis. (A) Histology shows a chronic inflammatory cellular infiltrate in relation to muscle fibres; (B) vascular injection over the insertion of the right medial rectus; (C) coronal CT shows enlargement of the right medial rectus

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – fig. A; J Nerad, K Carter and M Alford, from Oculoplastic and Reconstructive Surgery, in Rapid Diagnosis in Ophthalmology – Mosby 2008 – figs B and C)

Acute dacryoadenitis

Lacrimal gland involvement occurs in about 25% of patients with IOID. More commonly, dacryoadenitis occurs in isolation, resolves spontaneously and does not require treatment. Occasionally it may be caused by mumps, mononucleosis, and rarely bacteria.

Fig. 3.18 Left acute dacryoadenitis. (A) Swelling on the lateral aspect of the eyelid and an S-shaped ptosis; (B) injection of the palpebral portion of the lacrimal gland and adjacent conjunctiva; (C) axial CT shows enlargement of the gland and opacification of adjacent tissues

(Courtesy of R Bates – fig. B; A Pearson – fig. C)

Tolosa–Hunt syndrome

Tolosa–Hunt syndrome is a diagnosis of exclusion. It is a rare idiopathic condition caused by non-specific granulomatous inflammation of the cavernous sinus, superior orbital fissure and/or orbital apex. The clinical course is characterized by remissions and recurrences.

Wegener granulomatosis

Wegener granulomatosis may involve the orbit, often bilaterally, usually by contiguous spread from the paranasal sinuses or nasopharynx. Primary orbital involvement is less common. The possibility of Wegener granulomatosis should be considered in any patient with bilateral orbital inflammation, particularly if associated with sinus pathology. The antineutrophilic cytoplasmic antibody (cANCA) is a useful serological test.

Varices

Varices consist of weakened segments of the orbital venous system of variable length and complexity. Intrinsic to the circulation, they enlarge with increased venous pressure, their distensability varying with the residual thickness and strength of their walls. Most cases are unilateral and the most frequent site is upper nasal. Phleboliths are present in about 20% of cases.

Fig. 3.19 (A) Orbital varices before Valsalva; (B) with Valsalva; (C) eyelid varices; (D) conjunctival varices; (E) axial CT shows medial opacification and phleboliths; (F) left fat atrophy resulting in enophthalmos and deep superior sulcus

(Courtesy of G Rose – fig. A; A Pearson – figs E and F)

Lymphangioma

Lymphangiomas are not neoplasms but abortive, non-functional, benign, vascular malformations. Although haemodynamically isolated from the circulation, bleeding into the lumen may occur with resultant blood-filled ‘chocolate’ cysts. Lymphangiomas may be confused with orbital venous anomalies and haemangiomas.

Fig. 3.20 Anterior orbital lymphangioma with typical bluish discoloration

Fig. 3.21 (A) Severe proptosis due to bleeding from a posterior lymphangioma; (B) axial CT shows proptosis and orbital opacification; (C) oral involvement by lymphangioma

(Courtesy of A Pearson – figs A and B)

Direct carotid-cavernous fistula

Diagnosis

1 Presentation may be days or weeks after head injury with the classic triad of pulsatile proptosis, conjunctival chemosis and a whooshing noise in the head.

2 Signs are usually ipsilateral to the fistula but may be bilateral or even contralateral because of the vascular connections across the midline between the two cavernous sinuses.

• Severe epibulbar injection (Fig. 3.22A).

• Ptosis (due to 3rd nerve involvement) and haemorrhagic chemosis (Fig. 3.22B). The presence of ptosis may be helpful in differentiating this condition from acute TED.

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• Pulsatile proptosis associated with a bruit and a thrill, both of which can be abolished by ipsilateral carotid compression in the neck. A cephalic bruit may also be present.

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• Increased intraocular pressure from elevated episcleral venous pressure and orbital congestion.

• Anterior segment ischaemia, characterized by corneal epithelial oedema, aqueous cells and flare, and in severe cases iris atrophy, cataract and rubeosis iridis.

• Ophthalmoplegia occurs in 60–70% of cases due to the ocular motor nerve damage by initial trauma or an intracavernous aneurysm or by the fistula itself. The 6th nerve is most frequently affected because of its free-floating location within the cavernous sinus. The 3rd and 4th nerves, situated in the lateral wall of the sinus, are less frequently involved. Engorgement and swelling of extraocular muscles may also contribute to defective ocular motility.

• Fundus examination may show optic disc swelling, venous dilatation and intraretinal haemorrhages from venous stasis and impaired retinal blood flow. Preretinal or vitreous haemorrhages are rare.

2 Vision. Immediate visual loss may be due to ocular or optic nerve damage at the time of head trauma. Delayed visual loss may occur as a result of exposure keratopathy, secondary glaucoma, central retinal vein occlusion, anterior segment ischaemia or ischaemic optic neuropathy.

3 Special investigations. CT and MR may demonstrate prominence of the superior ophthalmic vein (Fig. 3.22C) and diffuse enlargement of extraocular muscles (Fig. 3.22D). Definitive diagnosis involves CT and MR angiography.

Fig. 3.22 Direct carotid-cavernous fistula. (A) Severe epibulbar injection; (B) haemorrhagic chemosis; (C) axial CT shows enlargement of the right superior ophthalmic vein; (D) coronal CT shows enlargement of extraocular muscles on the right

Treatment

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Most carotid-cavernous fistulae are not life-threatening; the organ at major risk is the eye. Surgery is indicated if spontaneous closure does not occur. A post-traumatic fistula is much less likely to close on its own than a spontaneous fistula because of higher blood flow. The current treatment of choice involves endovascular embolization with coils (Fig. 3.23) or balloons which may be transvenous or transarterial.

Fig. 3.23 Coil embolization of a direct carotid-cavernous fistula. (A) Early arterial phase catheter angiogram shows filling of the cavernous sinus (arrow) and superior ophthalmic vein (arrow head); (B) following deposition of coils in the cavernous sinus the fistula is closed and there is lack of retrograde flow in the superior ophthalmic vein

(Courtesy of J Trobe, from Neuro-ophthalmology, in Rapid Diagnosis in Ophthalmology, Mosby 2008)

Indirect carotid-cavernous fistula

In an indirect carotid-cavernous fistula (‘dural shunt’), the intracavernous portion of the internal carotid artery remains intact. Arterial blood flows through the meningeal branches of the external or internal carotid arteries indirectly into the cavernous sinus. Due to slow blood flow, the clinical features are more subtle than in a direct fistula. The condition may therefore be misdiagnosed or missed altogether.

Fig. 3.24 Left indirect carotid-cavernous fistula. (A) Mild epibulbar injection and chemosis; (B) 6th nerve palsy

(Courtesy of J Yanguela)

Dacryops

A dacryops is a ductal cyst of the lacrimal gland. It is a relatively uncommon orbital cystic lesion that is frequently bilateral.

Fig. 3.25 Dacryops

Dermoid cyst

An orbital dermoid cyst is a choristoma derived from displacement of ectoderm to a subcutaneous location along embryonic lines of closure. Dermoids are lined by keratinized stratified squamous epithelium (like skin), have a fibrous wall and contain dermal appendages such as sweat glands, sebaceous glands and hair follicles. Epidermoid cysts do not contain such adnexal structures. Dermoids may be (a) superficial or (b) deep, located anterior or posterior to the orbital septum respectively.

Superficial dermoid cyst

1 Presentation is in infancy with a painless nodule most commonly located in the superotemporal and occasionally the superonasal part of the orbit.

2 Signs

• A firm round smooth non-tender mass 1–2 cm in diameter (Fig. 3.26A), mobile under the skin but usually tethered to the adjacent periosteum.

• The posterior margins are easily palpable, denoting lack of deeper origin or extension.

3 CT shows a heterogeneous well-circumscribed lesion (Fig. 3.26B).

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4 Treatment is by excision in toto (Fig. 3.26C), taking care not to rupture the lesion, since leaking of keratin into the surrounding tissue results in severe granulomatous inflammation.

Fig. 3.26 (A) Superficial dermoid cyst; (B) axial CT shows a well-circumscribed heterogeneous lesion; (C) appearance at surgery

(Courtesy of K Nischal – fig. B; A Pearson – fig. C)

Deep dermoid cyst

1 Presentation is in adolescence or adult life.

2 Signs

• Proptosis, dystopia or a mass lesion with indistinct posterior margins (Fig. 3.27A).

• Rupture may incite an inflammatory reaction.

• Some deep dermoids, associated with bony defects, may extend into the inferotemporal fossa or intracranially.

3 CT shows a well-circumscribed cystic lesion (Fig. 3.27B).

4 Treatment by excision in toto is advisable because deep dermoids enlarge and may leak their contents into adjacent tissues inducing a painful granulomatous inflammation, often followed by fibrosis. If incompletely excised, dermoids may recur and cause persistent low-grade inflammation.

Fig. 3.27 (A) Left deep orbital dermoid cyst causing mild dystopia; (B) axial CT shows a well-circumscribed cystic lesion and bone remodelling

(Courtesy of A Pearson)

Sinus mucocele

A mucocele develops when the drainage of normal para-nasal sinus secretions is obstructed due to infection, allergy, trauma, tumour or congenital narrowing. A slowly expanding cystic accumulation of mucoid secretions and epithelial debris develops and gradually erodes the bony walls of the sinuses, causing symptoms by encroaching upon surrounding tissues. Orbital invasion occurs usually from frontal or ethmoidal mucoceles, and rarely from those arising in the maxillary sinus.

Fig. 3.28 (A) Left ethmoidal sinus mucocele causing dystopia; (B) coronal CT shows orbital involvement and indentation of the medial rectus

Encephalocele

An encephalocele is formed by herniation of intracranial contents through a congenital defect of the base of the skull. A meningocele contains only dura whilst a meningoencephalocele also contains brain tissue. Orbital encephalocele may be (a) anterior (fronto-ethmoidal) or (b) posterior, which is associated with dysplasia of the sphenoid bone.

Fig. 3.29 (A) Anterior superomedial encephalocele causing proptosis and down and out dystopia; (B) posterior encephalocele causing proptosis and inferior dystopia; (C) coronal CT of posterior encephalocele showing a large bony defect

(Courtesy of A Pearson – fig. C)

Fig.3.30 Associations of encephalocele (A) Hypertelorism; (B) cleft palate; (C) morning glory anomaly

(Courtesy of K Nischal – fig A; Moorfields Eye Hospital – figs B and C)

Capillary haemangioma

Capillary haemangioma is the most common tumour of the orbit and periorbital areas in childhood. Girls are affected more commonly than boys. It may present as a small isolated lesion of minimal clinical significance, or as a large disfiguring mass that can cause visual impairment and systemic complications. The tumour is composed of anastomosing small vascular channels without true encapsulation (Fig. 3.31A).

Fig. 3.31 Capillary haemangioma. (A) Histology shows irregular capillary channels of varying size; (B) large preseptal tumour causing ptosis and purple cutaneous discoloration; (C) inferior preseptal tumour; (D) involvement of forniceal conjunctiva

(Courtesy of J Harry – fig. A; K Nischal – figs C and D)

Diagnosis

The tumour is classified according to its location with respect to the skin and orbital septum as follows: (a) cutaneous, (b) purely preseptal, (c) preseptal with an extraconal element and (d) combination of preseptal, extraconal and intraconal.

1 Presentation is usually in the first few weeks of life (approximately 30% are present at birth).

2 Signs

• Superficial cutaneous lesions are bright red.

• Preseptal tumours appear dark blue or purple through the overlying skin (Fig. 3.31B and C) and are most frequently located superiorly.

• A large tumour may enlarge and change in colour to a deep blue during crying or straining, but both pulsation and a bruit are absent.

• Deep orbital tumours give rise to unilateral proptosis without skin discoloration.

• Haemangiomatous involvement of the palpebral or forniceal conjunctiva is common and may be an important diagnostic clue (Fig. 3.31D).

• Additional haemangiomas on the eyelids or elsewhere are common.

3 CT may be required for deep involvement when the diagnosis is not apparent on inspection. The lesion appears as a homogeneous enhancing soft tissue mass in the anterior orbit or as an extraconal mass with ‘finger-like’ posterior expansions (Fig. 3.32A). The orbital cavity may show enlargement but there is no bony erosion.

4 Ultrasound is used to demonstrate the anatomical relations and extent of the tumour (Fig. 3.32B).

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5 The course is characterized by rapid growth 3–6 months after diagnosis (Fig. 3.33), followed by a slower phase of natural resolution in which 30% of lesions resolve by the age of 3 years and 70% by the age of 7 years.

Fig. 3.32 Imaging of capillary haemangioma. (A) Axial enhanced CT shows a homogeneous intraconal orbital soft tissue mass; (B) ultrasound of a preseptal lesion with an intraorbital component

(Courtesy of A Pearson – fig. A; K Nischal – fig. B)

Fig. 3.33 Growth of capillary haemangioma. (A) At presentation; (B) several months later

Cavernous haemangioma

Cavernous haemangioma is a vascular malformation that occurs in adults, with a female preponderance of 70%. Although it may develop anywhere in the orbit, it most frequently occurs within the lateral part of the muscle cone just behind the globe, and behaves like a low-flow arteriovenous malformation.

Fig. 3.34 Cavernous haemangioma. (A) Histology shows congested varying-sized endothelial-lined vascular channels separated by fibrous septae; (B) right axial proptosis; (C) axial CT shows a well-circumscribed retrobulbar oval lesion and proptosis; (D) the tumour is encapsulated and relatively easy to remove

(Courtesy of A Pearson – figs B, C and D)

Pleomorphic lacrimal gland adenoma

Pleomorphic adenoma (benign mixed-cell tumour) is the most common epithelial tumour of the lacrimal gland and is derived from the ducts and secretory elements including myoepithelial cells.

Fig. 3.35 Pleomorphic lacrimal gland adenoma. (A) Histology shows glandular tissue and squamous differentiation with keratin formation; (B) inferonasal dystopia due to a tumour arising from the orbital lobe; (C) coronal CT shows an oval mass

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth and Heinemann 2001 – fig. A; A Pearson – figs B and C)

Fig. 3.36 Pleomorphic lacrimal gland adenoma arising from the palpebral lobe. (A) Eyelid swelling without dystopia; (B) eversion of the upper eyelid reveals the tumour

Fig. 3.37 Lateral orbitotomy. (A) Incision of temporalis muscle; (B) drilling of underlying bone for subsequent wiring; (C) removal of the lateral orbital wall and the tumour; (D) repair of the lateral orbital wall and temporalis muscle

Lacrimal gland carcinoma

Lacrimal gland carcinoma is a rare tumour which carries a high morbidity and mortality. In order of frequency the main histological types are: (a) adenoid cystic, (b) pleomorphic adenocarcinoma, (c) mucoepidermoid and (d) squamous cell.

Fig. 3.38 Lacrimal gland carcinoma. (A) Histology of adenoid cystic carcinoma shows nests of basaloid cells with solid and cribriform areas; (B) dystopia, proptosis, periorbital oedema and epibulbar congestion due to extension involving the superior orbital fissure; (C) coronal CT shows contiguous erosion of bone and spotty calcification in the tumour

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001; A Pearson – fig. C)

Optic nerve glioma

Optic nerve glioma is a slow-growing, pilocytic astrocytoma which typically affects children. Approximately 30% of patients have associated NF1 (see Ch. 19) and in these patients the prognosis is better. Malignant gliomas are rare and almost always occur in adults. They have a very poor prognosis with almost certain death within 1 year of diagnosis.

Fig. 3.39 Optic nerve glioma. (A) Histology shows spindle-shaped pilocytic astrocytes and glial filaments; (B) proptosis with inferior dystopia; (C) axial CT shows fusiform optic nerve enlargement

(Courtesy of J Harry – fig. A; A Pearson – fig. C)

Fig. 3.40 Optic nerve meningioma. (A) Histology of meningothelial type; (B) histology of psammomatous type; (C) defective elevation of the right eye; (D) axial CT of a small tumour shows slight thickening and calcification; (E) post-contrast T1-weighted MR shows involvement of the orbital and intracanalicular segments of the optic nerve (arrow)

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001 – figs A and B; A Pearson – fig. D; J Trobe, from Neuro-ophthalmology, in Rapid Diagnosis in Ophthalmology, Mosby 2006 – fig. E)

Optic nerve sheath meningioma

Optic nerve sheath meningiomas arise from meningothelial cells of the arachnoid villi surrounding the intraorbital or, less commonly, the intracanalicular portion of the optic nerve. In some cases the tumour merely encircles the optic nerve whilst in others it invades the nerve by growing along the fibrovascular pial septa. Primary optic nerve sheath meningiomas are less common than optic nerve gliomas and, as with other meningiomas, typically affect middle-aged women.

Plexiform neurofibroma

Plexiform neurofibroma is the most common peripheral neural tumour of the orbit and occurs almost exclusively in association with NF1.

Fig. 3.41 (A) Plexiform neurofibroma causing periorbital involvement and facial disfigurement; (B) CT shows orbital involvement and inferior dystopia

(Courtesy of A Pearson)

Isolated neurofibroma

Isolated (localized) neurofibroma is less common and is associated with NF1 in about 10% of cases.

Lymphoma

Lymphomas of the ocular adnexa constitute approximately 8% of all extranodal lymphomas. They represent one end of the spectrum of lymphoproliferative lesions, at the other end of which lies benign reactive lymphoid hyperplasia. Accurate diagnosis of the type of lymphoma has improved considerably with the introduction of immunological staining methods. The vast majority of orbital lymphomas are of B-cell origin and most are composed of ‘small’ B cells (Fig. 3.42A).

Fig. 3.42 Orbital lymphoma. (A) Histology shows neoplastic lymphoid cells; (B) involvement of the superior orbit causing proptosis and inferior dystopia; (C) axial T1-weighted MR of the same patient shows a large orbital soft tissue mass and proptosis; (D) anterior lesion

(Courtesy of J Harry – fig. A; A Pearson – figs B and C)

Embryonal sarcoma

Embryonal sarcoma (traditionally designated ‘rhabdomyosarcoma’) is the most common primary orbital malignancy of childhood. The tumour is derived from undifferentiated mesenchymal cell rests, which have the potential to differentiate into striated muscle. They do not arise from striated muscle, and the term rhabdomyosarcoma is appropriate only if there is evidence of differentiation into muscle. The main role of the ophthalmologist is diagnosis by incisional biopsy, followed by prompt referral to a paediatric oncologist.

Fig. 3.43 Histology of embryonal sarcoma. (A) Undifferentiated tumour with loosely-arranged proliferation of mesenchymal cells; (B) differentiated tumour shows many elongated strap-like cells with eosinophilic cytoplasm (rhabdomyoblasts); (C) differentiated tumour in which the rhabdomyoblast in the centre of the field has cross-striations; Masson trichrome stain

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann 2001)

Fig. 3.44 Embryonal sarcoma. (A) Involvement of the anterior inferior orbit; (B) swelling and erythema of eyelid skin; (C) coronal CT shows a poorly defined mass in the superotemporal orbit; (D) axial T2-weighted MR of an advanced retrobulbar tumour shows a large mass with indentation of the globe and proptosis

(Courtesy of M Szreter – fig. B; A Pearson – figs B and C)

Adult metastatic tumours

Orbital metastases are an infrequent cause of proptosis and are much less common than metastases to the choroid. If the orbit is the initial manifestation of the tumour, the ophthalmologist may be the first person to see the patient. In order of frequency the most common primary sites are breast, bronchus, prostate, skin (melanoma), gastrointestinal tract and kidney.

Fig. 3.45 Metastatic renal carcinoma. (A) Proptosis; (B) axial CT shows a non-encapsulated retrobulbar mass

(Courtesy of A Pearson – fig. B)

Childhood metastatic tumours

Neuroblastoma

1 Systemic features. Neuroblastoma is one of the most common childhood malignancies. It arises from primitive neuroblasts of the sympathetic chain, most commonly in the abdomen (Fig. 3.46A), followed by the thorax and pelvis. Presentation is usually in early childhood; in almost half of all cases the tumour is disseminated at diagnosis with an appalling prognosis.

2 Orbital metastases may be bilateral and typically present with an abrupt onset of proptosis accompanied by a superior orbital mass and lid ecchymosis (Fig. 3.46B).

Fig. 3.46 Neuroblastoma. (A) Axial CT shows a tumour adjacent to the kidney; (B) bilateral orbital metastases

(Courtesy of B Zitelli and H Davis, from Atlas of Pediatric Physical Diagnosis, Mosby 2002)

Langerhans cell histiocytosis

1 Systemic features. Langerhans cell histiocytosis is a rare group of disorders due to clonal proliferations of histiocytes. Presentation ranges from localized disease usually causing bone destruction (eosinophilic granuloma), through multifocal bone involvement to a fulminant systemic disease. Soft tissues are less commonly involved, but cutaneous and visceral involvement may occur.

2 Orbital involvement consists of unilateral or bilateral osteolytic lesions and soft tissue involvement, typically in the superotemporal quadrant (Fig. 3.47). Patients with solitary lesions tend to have a more benign course and respond well to treatment with local curettage and intralesional steroid injection or radiotherapy. Systemic disease responds poorly and has a high mortality.

Fig 3.47 Langerhans cell histiocytosis

(Courtesy of D Taylor)

Orbital invasion from adjacent structures

Sinus tumours

Malignant tumours of the paranasal sinuses, although rare, may invade the orbit and carry a poor prognosis unless diagnosed early. It is therefore important to be aware of both their otorhinolaryngological and ophthalmic features.

1 Maxillary carcinoma is by far the most common sinus tumour to invade the orbit (Fig. 3.48).

• Otorhinolaryngological manifestations include facial pain and swelling, epistaxis and nasal discharge.

• Ophthalmic features include upward dystopia, diplopia and epiphora.

2 Ethmoidal carcinoma may cause lateral dystopia.

3 Nasopharyngeal carcinoma may spread to the orbit through the inferior orbital fissure; proptosis is a late finding.

Fig. 3.48 Advanced maxillary carcinoma showing facial swelling and upward dystopia

Bony invasion

1 Intracranial meningioma arising from the sphenoidal ridge may invade the orbit by direct spread and cause proptosis (see Fig. 19.56). Occasionally tumours arising from the tuberculum sellae or olfactory groove may invade the orbital through the superior orbital fissure or optic canal.

2 Fibrous dysplasia is a benign developmental disorder leading to slowly-developing irregular expansion of bone with a mass effect on adjacent structures (Fig. 3.49A). Within the orbital region this may cause facial asymmetry, proptosis, dystopia (Fig. 3.49B) and visual loss. Most orbital disease is due to the monostotic form whereas polyostotic disease is associated with endocrine disorders and cutaneous pigmentation (McCune-Albright syndrome).

Fig. 3.49 Bony invasion of the orbit by fibrous dysplasia (A) Coronal CT scan shows involvement of the floor and medial wall of the right orbit; (B) upward dystopia of the right eye

(Courtesy of A Pearson)

Orbital invasion from eyelid, conjunctival and intraocular tumours

Orbital invasion may occur from eyelid malignancies such as basal cell carcinoma, squamous cell carcinoma or sebaceous gland carcinoma, from conjunctival tumours, in particular melanoma (Fig. 3.50A), and from intraocular tumours such as choroidal melanoma or retinoblastoma (Fig. 3.50B).

Fig. 3.50 (A) Orbital invasion by conjunctival melanoma; (B) orbital invasion by retinoblastoma

Surgical procedures

Removal of an eye or the contents of the orbit may be indicated for intraocular or orbital malignancy or where the eye is blind and painful or unsightly. A number of different surgical and rehabilitation techniques are available.

Evisceration

Evisceration involves removal of the entire contents of the globe leaving the sclera and extraocular muscles intact. Generally the cornea is removed (Fig. 3.51) to provide access to the ocular contents. Retention of the sclera and lack of disruption of the extraocular muscles is considered to provide somewhat better motility than is achieved after enucleation. Evisceration provides disrupted and incomplete material for histology and should not be undertaken in the presence of suspected intraocular malignancy.

Fig. 3.51 Appearance following evisceration

Exenteration

Exenteration involves removal of the globe and the soft tissues of the orbit. Indications include the following:

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1 Orbital malignancies that may be primary or where tumours have invaded the orbit from the eyelids, conjunctiva, globe and bony surrounds and where other forms of treatment are unlikely to be effective. Anteriorly sited tumours may allow relative sparing of tissue at the posterior orbit, and posterior tumours may allow sparing of eyelid skin which helps in lining the new socket (Fig. 3.52A and B). Prostheses following exenteration can be temporarily stuck onto the surrounding skin, mounted on glasses (Fig. 3.53), or secured with osseo-integrated magnets mounted on the orbital rim bones. The socket may be lined with skin or a split-skin graft or left to heal by secondary intention.

2 Non-malignant disease such as orbital mucormycosis is a rare indication.

Fig. 3.52 Exenteration. (A) With sparing of the eyelids; (B) with sacrificing the eyelids

(Courtesy of A Pearson)

Fig. 3.53 (A) Healed exenteration; (B) prosthesis attached to glasses

(Courtesy of A Pearson)

Rehabilitation

Orbital implants

Enucleation or evisceration leads to reduction in volume of the orbital contents. A large prosthetic eye is not a satisfactory solution to this due to poor motility and stretching of the lower lid under its weight.

1 Post-enucleation socket syndrome (PESS) is caused by failure to correct the volume deficit. It is characterized by a deep upper lid sulcus, ptosis, enophthalmos (Fig. 3.54) and backwards rotation of the top of the prosthesis.

2 Implants. Ball implants are usually placed at the time of initial eye removal. Secondary placement can also be made after an initial procedure to remove the eye or to replace an existing implant.

3 Materials used for implants may be solid such as silicone, methylmethacrylate and ceramic, or have a porous structure such as polyethylene and hydroxyapatite. The latter allow fibrovascular ingrowth, enabling the implant to be drilled to take a peg to assist movement of the overlying artificial eye. The motility of unpegged implants is usually good.

4 Extrusion (Fig. 3.55) is a significant concern with all implants. Careful placement of the implant ensuring it is sufficiently deep and is well covered with vascularized tissue is more important than the choice of implant material.

Fig. 3.54 Right post-enucleation socket syndrome and poor motility

Fig. 3.55 Extruding orbital implant

Ocular prosthesis

After enucleation or evisceration a conformer (Fig. 3.56) made of silicone or acrylic material is placed to support the conjunctival fornices and remains in place until the socket is fitted with an artificial eye (Fig. 3.57). Initial socket impression moulds can usually be taken at around 6–8 weeks and a temporary artificial eye placed whilst waiting for a prosthesis shaped to fit the individual socket and matched to the fellow eye.

Fig. 3.56 Conformer in place

Fig. 3.57 Artificial eye

Crouzon syndrome

Crouzon syndrome is caused primarily by premature fusion of the coronal and sagittal sutures.

Fig. 3.58 Crouzon syndrome. (A) Proptosis, midfacial hypoplasia and mandibular prognathism; (B) ‘V’ exotropia

Apert syndrome

Apert syndrome (acrocephalosyndactyly) is the most severe of the craniosynostoses and may involve all the cranial sutures.

Fig. 3.59 Apert syndrome. (A) Mild shallow orbits, midfacial hypoplasia and ‘parrot-beak’ nose; (B) syndactyly

Pfeiffer syndrome

Fig. 3.60 Pfeiffer syndrome. (A) Midfacial hypoplasia and down-slanting palpebral fissures; (B) broad great toe

(Courtesy of K Nischal)