Ординатура / Офтальмология / Английские материалы / Oxford American Handbook of Ophthalmology_Tsai, Denniston, Murray_2011

486 CHAPTER 14 Orbit

Investigation

Orbital imaging: CT shows opacification of frontal or ethmoidal sinus (+loss of ethmoidal septae) with a bony defect allowing intraorbital protrusion. B-scan US shows a well-defined lesion with low internal reflectivity.

Treatment

Refer to an ENT specialist to excise the mucocele, restore sinus drainage, or obliterate the sinus cavity (in recurrent cases).

Cephalocele

These are developmental malformations resulting in herniation into the orbit of brain (encephalocele), meninges (meningocele), or both (meningoencephalocele). They may be anterior (frontoethmoidal bony defects) or posterior (sphenoid dysplasia). Encephaloceles may be associated with other craniofacial or ocular abnormalities; posterior encephaloceles may be associated with neurofibromatosis-1 and morning glory syndrome.

Clinical features

Pulsatile proptosis may increase with Valsalva maneuver but have no bruit (cf. arteriovenous fistulae).

Anterior lesions

The encephalocele may be visible, and proptosis is usually anterotemporal.

Posterior lesions

The encephalocele is not visible and the proptosis is usually anteroinferior.

Investigation

Orbital imaging: CT shows a defect in the orbital wall.

ORBITAL TUMORS: LACRIMAL AND NEURAL 487

Orbital tumors: lacrimal and neural

Lacrimal gland

Pleomorphic adenoma

This is the most common lacrimal neoplasm and accounts for up to 25% of all lacrimal fossa lesions. The tumor derives from epithelial and mesenchymal tissue, hence the term benign mixed cell tumor. It may arise from either lobe, most commonly the orbital.

The neoplasm occurs in middle age with a slight male bias (M:F 1.5:1). Malignant transformation occurs at around 10% in 10 years.

Clinical features

•Gradual painless proptosis (inferonasal), ophthalmoparesis, choroidal folds, palpable mass of the superomedial orbit (orbital lobe tumors may not be palpable).

Investigation

•US shows a round lesion with medium to high reflectivity and regular acoustic structure.

•CT/MRI shows a well-defined round lesion ± bone remodeling.

Treatment

This involves surgical removal of the whole tumor with intact capsule without prior biopsy (risk of seeding). This is usually done with an anterior (palpebral lobe tumors) or lateral (orbital lobe tumors) orbitotomy. Prognosis is excellent with complete excision.

Lacrimal carcinomas

The most common malignant tumor of the lacrimal gland is the adenoid cystic carcinoma, followed by the mucoepidermoid carcinoma and the pleomorphic adenocarcinoma. They occur at a similar age to that of adenomas but cause more rapid proptosis and ophthalmoparesis, and orbital pain from perineural spread is common.

Imaging shows an irregular, poorly defined lesion with bony destruction. Treatment is seldom curative but consists of exenteration ± radiotherapy. Prognosis is very poor.

Neural

Optic nerve glioma

This is an uncommon slow-growing tumor of astrocytes that usually occurs in children and has a strong association with neurofibromatosis-1. It usually presents with gradual dVA (although this often stabilizes), disc swelling or atrophy, and proptosis. Isolated optic nerve involvement occurs in 22%, but most cases involve the chiasm (72%), often with midbrain and hypothalamic involvement.

Imaging shows fusiform enlargement of the optic nerve ± chiasmal mass. Observation is recommended for patients with isolated optic nerve involvement distant from the chiasm, good vision, and nondisfiguring proptosis. Progress is monitored with serial MRI scans.

488 CHAPTER 14 Orbit

Surgical excision is indicated for pain, severe proptosis, or posterior spread threatening the chiasm. Chiasmal or midbrain involvement may be an indication for chemotherapy or radiotherapy.

Prognosis for life is good for optic nerve–restricted tumors but worsens with more posterior involvement.

Optic nerve sheath meningioma

This is a rare benign tumor of meningothelial cells of the meninges that usually occurs in middle age and has a slight female bias (F:M 1.5:1). There is an association with neurofibromatosis-2. It usually presents with gradual dVA, disc swelling or atrophy, optociliary shunt vessels (30%), proptosis, and ophthalmoparesis.

Imaging shows tubular enlargement of the nerve with “tram-track” enhancement of the sheath ± calcification. Observation is recommended if VA is good.

Surgical excision is indicated for blind eyes, severe proptosis, or threat to the chiasm. Prognosis for life is good.

Neurofibroma

Neurofibromas are uncommon benign tumors of peripheral nerves. Plexiform neurofibroma presents in childhood and is strongly associ-

ated with neurofibromatosis-1. Anterior involvement results in a “bag- of-worms” mass causing an S-shaped lid deformity. The tumor is poorly defined and not encapsulated. Surgical excision is difficult and may require repeated debulking.

Isolated neurofibroma presents in adulthood with gradual proptosis. The tumor is well circumscribed, and surgical excision is usually straightforward.

Schwannoma

This is an uncommon slow-growing tumor of peripheral or cranial nerves that is usually benign but may be malignant. The tumor usually presents in adulthood. There is an association with neurofibromatosis.

It is usually located in the superior orbit and presents as a gradually enlarging nontender mass (often cystic) with proptosis, dVA, and restricted motility.

Treatment is with complete surgical excision, which has a good prognosis.

ORBITAL TUMORS: VASCULAR 489

Orbital tumors: vascular

Cavernous hemangioma

This is the most common benign orbital neoplasm of adults. It is a hamartoma but does not usually present until young adulthood, most notably during pregnancy (accelerated growth). It is usually intraconal.

Clinical features

•Proptosis (usually axial due to intraconal location); later restricted motility, choroidal folds, and dVA.

Investigation

•US: well-circumscribed intraconal lesion with high internal reflectivity.

•CT/MRI: well-circumscribed intraconal lesion with mild to moderate enhancement.

Treatment

Most may be observed, but symptomatic lesions should be completely excised, if possible. For apical lesions, decompression may be indicated to preserve vision.

Capillary hemangioma

This is a type of hamartoma (congenital tumors of tissues normal to that location). Very large tumors may be consumptive (Kasabach–Merritt syndrome: dplatelets, dHb, dclotting factors) or cause high-output cardiac failure.

Superficial lesions (strawberry nevus)

These are bright red tumors that usually appear before 2 months of age, reach full size by 1 year, and involute by 6 years. They may be disfiguring and/or may cause amblyopia by obscuration of the visual axis or, more commonly, associated astigmatism. In these cases, treatment (usually with systemic propranolol or corticosteroids) may be indicated.

Deep lesions

These may not be visible but cause variable proptosis (worsens with Valsalva maneuver or crying). With time, partial involution occurs in most of these lesions, but large tumors may be treated (with corticosteroids or radiotherapy).

Lymphangioma

This is a rare hamartoma of lymph vessels that usually presents in childhood. They increase in size with head-down posture, Valsalva maneuver, and viral illness. Superficial lesions are visible as cystic spaces of the lid or conjunctiva that may also contain blood. Deep lesions may cause gradual proptosis or present acutely with orbital pain and dVA due to hemorrhage (“chocolate cyst”).

Most lesions are observed. If a sight-threatening bleed occurs, the lesion may be drained, but surgery is difficult. Injection of cyanoacrylate glue or fibrin glue may aid in surgical debulking.

490 CHAPTER 14 Orbit

Orbital tumors: lymphoproliferative

Benign reactive lymphoid hyperplasia

This is an uncommon polyclonal proliferation of lymphoid tissue that usually occurs in the superoanterior orbit, often involving the lacrimal gland. It may present with gradual proptosis and/or a palpable firm rubbery mass. It usually responds to corticosteroids or radiotherapy, although some cases require cytotoxics. Progression to lymphoma occurs in up to 25% by 5 years.

Atypical lymphoid hyperplasia is intermediate between benign reactive hyperplasia and lymphoma and is characterized by a very homogeneous pattern with larger nuclei.

Malignant orbital lymphoma

This is an uncommon low-grade proliferation of B cells (non-Hodgkin’s type) usually arising in the elderly. It usually presents with gradual proptosis and/or a palpable firm rubbery mass. It is usually unilateral, but bilateral involvement occurs in 25%; systemic involvement is present in 40% at diagnosis and in 60% within 5 years.

Treatment (radiotherapy or chemotherapy) depends on the grade and spread of tumor; a systemic workup is necessary in all cases.

Langerhans cell histiocytosis (LCH)

This is a rare proliferative disorder of childhood. It comprises a spectrum of disease from the unifocal, relatively benign eosinophilic granuloma to the disseminated Letterer–Siwe form. In eosinophilic granuloma, orbital involvement is common and presents as rapid proptosis with a superotemporal swelling.

Surgical curretage with injection of intralesional corticosteroids is usually curative. Bilateral proptosis may occur in disseminated LCH.

ORBITAL TUMORS: OTHER 491

Orbital tumors: other

Rhabdomyosarcoma

This is the most common primary orbital malignancy in children. It usually arises in the first decade and has a slight male bias (M:F 1.6:1). The tumor arises from pluripotent mesenchymal tissue.

Histologically, it may be differentiated into embryonal (most common), alveolar, and pleomorphic types. It is usually intraconal (50%) or within the superior orbit (25%).

Clinical features

•Acute/subacute proptosis, ptosis and orbital inflammation; it may therefore mimic inflammatory conditions such as orbital cellulitis.

Investigation

•B-scan US: irregular but well-defined edges, low to medium reflectivity.

•CT/MRI: irregular but well-defined mass ± bony erosion.

Treatment

A biopsy (to confirm diagnosis) and systemic workup (to establish spread) are necessary in all cases. Surgical excision is possible for well-circum- scribed localized tumors. Combined radiotherapy and chemotherapy is given for more extensive tumors.

Fibrous histiocytoma

This is an uncommon tumor that may affect middle-aged adults or children who have had orbital radiotherapy. It may be benign or malignant. The tumor is usually located superonasally and presents with gradual proptosis, dVA, and restricted motility. Treatment is by surgical excision, but recurrences are common.

Metastases

Orbital metastases are uncommon. In around half of all cases, they precede the diagnosis of the underlying tumor (Table 14.10). They usually present aggressively with fairly rapid proptosis, restricted motility, cranial nerve involvement, and orbital inflammation. Scirrhous tumors (e.g., some breast, prostate, and gastric tumors) may cause enophthalmos.

Table 14.10 Primary tumors metastasizing to the orbit

492 CHAPTER 14 Orbit

Vascular lesions

Orbital varices

These are congenital venous enlargements that may present from childhood on. They are usually unilateral and located in the medial orbit.

Clinical features

•Intermittent proptosis and/or visible varix (worse with increased venous pressure, i.e., Valsalva maneuver and in head-down position); occasional thrombosis or hemorrhage.

Treatment

Surgery is difficult but is indicated if the condition is severe or sight threatening. Incomplete excision is common.

Arteriovenous fistula

These are abnormal anastamoses between the arterial and venous circulation. The carotid–cavernous fistula is a high-flow system arising from direct communication between the intracavernous internal carotid artery and the cavernous sinus.

The dural shunt (also known as indirect carotid–cavernous fistula) is a low-flow system arising from dural arteries (branches of the internal and external carotid arteries) communicating with the cavernous sinus.

Arteriovenous fistulae may be congenital (e.g., Wyburn–Mason syndrome), secondary to trauma (particularly in young adults), or occur spontaneously (most cases in older people).

Clinical features

Carotid–cavernous fistula (direct)

•dVA, diplopia, audible bruit.

•Pulsatile proptosis with a bruit, orbital edema, injected chemotic conjunctiva, iIOP, variable ophthalmoplegia (usually involving CN III and CN VI), retinal vein engorgement, RAPD, disc swelling.

Dural shunt (indirect carotid–cavernous fistula)

•May be asymptomatic; pain, cosmesis.

•Chemosis, episcleral venous engorgement, iIOP.

Investigation

Orbital imaging: B-scan US, CT, and MRI show a dilated superior ophthalmic vein and mild thickening of the extraocular muscles.

Treatment

•High-flow carotid–cavernous fistulae may cause visual loss in up to 50% of cases and require closure by catheter embolization.

•Low-flow dural shunts spontaneously close by thrombosis in up to 40% cases. Intervention is reserved for cases with glaucoma, dVA, diplopia, or severe pain.

Intraocular tumors

Iris tumors 494

Ciliary body tumors 496

Choroidal melanoma 497

Choroidal nevus 500

Choroidal hemangiomas 501

Other choroidal tumors 503

Retinoblastoma (Rb) 505

Retinal hemangiomas 507

Other retinal tumors 509

RPE tumors 510

Lymphoma 512

494 CHAPTER 15 Intraocular tumors

Iris tumors

Uveal melanoma

Uveal melanoma is the most common primary malignant intraocular tumor of Caucasian adults, with a lifetime incidence of around 0.05%. Risk factors include race (light >> dark pigmentation), age (old > young), and underlying disorders such as ocular melanocytosis and dysplastic nevus syndrome. It is slightly more common in men than women.

Tumors arise from neuroectodermal melanocytes of the choroid, ciliary body, or iris.

Iris melanoma

Compared to the other uveal melanomas, iris tumors are less common (8% of uveal tumors), present at a younger age (40–50 years), and have a better prognosis. Histologically, they usually comprise spindle cells alone or spindle cells with benign nevus cells. See Table 15.1 for differential diagnosis.

Clinical features

•Usually asymptomatic; patient may note a spot or diffuse color change.

•Iris nodule is most commonly light to dark brown, well-circumscribed, usually inferior iris. It may be associated with hyphema, increase

of intraocular pressure (IOP) (tumor or pigment cell blockage of trabecular meshwork), or cataract. Transcleral illumination may help demarcate posterior extension.

Risk factors for malignancy

These include size (>3 mm diameter, >1 mm thickness), rapid growth, prominent intrinsic vascularity, pigment dispersion, increased IOP, and iris splinting (uneven dilation).

Investigations

•B-scan ultrasound: size, extension, composition.

•Biopsy: consider fine needle aspiration (simple, safe, but scanty sample with no architecture) or incisional biopsy (corneal/limbal wound, risk of hyphema, and potential for monocular diplopia).

Treatment

Specialist consultation and advice should be obtained. Options include the following:

•Observation: small, asymptomatic tumors with no evidence of growth; intervention may not be necessary.

•Excision: consider iridectomy/iridocyclectomy.

•Radiotherapy: proton beam radiotherapy or brachytherapy.

•Enucleation: rarely indicated (nonresectable, extensive aqueous seeding or painful, blind eye).

Prognosis

Most patients do well and never develop metastatic disease. Poor prognostic features include large tumor size, ciliary body or extrascleral extension, and diffuse or annular growth pattern.

IRIS TUMORS 495

Table 15.1 Differential diagnosis of iris melanoma

Box 15.1 Suspicious features in an iris nevus

•Size (>3 mm diameter, >1 mm thickness)

•Rapid growth

•Prominent intrinsic vascularity

•Pigment dispersion

•iIOP

•Iris splinting (uneven dilation)

•Pupillary peaking

•Uveal ectropion

Iris nevus

These common lesions require yearly ophthalmic observation unless there are suspicious features (Box 15.1), which require closer observation and photography.

Clinical features

•Usually asymptomatic; patient may note a spot on the iris.

•Small (<3 mm diameter, <0.5 mm thick), defined, pigmented stromal lesion; pupillary peaking or uveal ectropion occasionally occur in nevi.

Iris metastasis

These are typically amelanotic solid tumors, which may cause complications such as secondary open-angle glaucoma (clogging or infiltration of trabecular meshwork with tumor cells), hyphema, and pseudohypopyon. In most cases patients are already known to have a malignancy elsewhere, but in some patients the iris lesion is the presenting feature and requires extensive workup with an oncologist.