Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

■Casualty : if visual loss is progressing rapidly arrange admission for investigations; otherwise, arrange an early clinic appointment.

■Clinic : review results of imaging. Treatment depends on the diagnosis. If a suprasellar tumour is present, involve an endocrinologist.

Follow–up Long-term management of the underlying aetiology by a neuro-ophthalmologist and appropriate multidisciplinary team is usually required.

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Nutritional and toxic optic neuropathy

Nutritional and Toxic

Optic Neuropathy

Background In developed nations this condition typically affects male alcoholic smokers but also those with poor diet, B12 deficiency, or on certain drugs, e.g. ethambutol, isoniazid.

Symptoms Painless, bilateral, central scotoma or reduced vision occurring over days to weeks.

Signs Sluggish pupil reactions (but usually no RAPD because eyes are affected equally), decreased colour vision and VA, and field defects. Optic discs usually appear normal but are occasionally mildly swollen and may appear atrophic later.

History and examination Ask about alcohol intake, smoking, abuse of methanol, dietary intake (vegan?), medications, any overdoses (quinine), pernicious anaemia, stomach resection or other causes of malabsorption. Record VA, colour vision, confrontation visual fields, and dilated fundal appearance. Exclude proptosis and dysmotility.

Differential diagnosis Consider other optic neuropathies (compressive, demyelinating, traumatic, infiltrative, inflammatory, radiation) and quinine overdose.

Investigations Arrange an MRI scan to exclude a compressive lesion. Check serum B12, folate, syphilis serology, FBC and film, and LFTs to detect undeclared alcohol abuse. Investigate for infiltrative, inflammatory, or inherited optic neuropathy if indicated (p. 662 and p. 666). Request Humphrey 24–2 visual field test (colour perimetry may reveal larger central scotomas).

Treatment

■Casualty : advise to stop smoking and drinking alcohol and improve diet, if appropriate, and offer referral to alcohol or smokers’ support services. Prescribe multivitamins. Refer to neuro-ophthalmology clinic within 1 month.

■Clinic : confirm the diagnosis, check results, and repeat VA, colour vision, visual fields, and dilated fundoscopy. In tobacco

weekly until no further improvement then 1 mg every 2 months for 6 months. Do not use cyanocobalamin.

Follow–up Review initially in a few weeks to confirm the diagnosis then 3–6 monthly. A slow recovery is expected if smoking stops. The role of vitamins is uncertain but advisable.

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Hereditary optic neuropathy

Hereditary Optic Neuropathy

Background Hereditary optic neuropathies may be autosomal dominant (Kjer or dominant optic atrophy), mitochondrially inherited (Leber’s hereditary optic neuropathy, LHON), or associated with other syndromes (Behr, Wolfram, Friedrich’s Ataxia, Charcot-Marie-Tooth) or neurological problems (deafness, peripheral neuropathy, ataxia).

Clinical features

■Dominant optic atrophy: affects children but usually presents in adult life with reduced vision (>6/18 in 40%; only 17% are <6/60) that tends to be very slowly progressive over years. Optic atrophy may be an incidental finding. Rarely, patients may have nystagmus. Family history is usually positive.

■Leber’s hereditary optic neuropathy : affects any age but typically those 15–35 years. About 60% of males and 10% of females with a mutation will develop subacute sequential optic neuropathy with visual loss to 6/60 or worse. The second eye is affected within 15 months. Telangiectatic disc vessels sometimes occur, causing disc swelling that does not leak significantly on fluorescein angiography. Only 4% of those with 11778 mitochondrial DNA mutation improve, compared to 40% of those with the less common 14484 mutation. Only 50% of cases will have a positive family history; ask about affected male cousins on the maternal side of the family.

Differential diagnosis Consider other causes of bilateral symmetrical optic neuropathy (mostly nutritional or toxic). It is very unlikely for bilateral central scotomas to be compressive in aetiology. MS and normal tension glaucoma may cause progressive bilateral optic atrophy. ERG excludes cone dystrophy.

Investigations Request an MRI of the brain and orbits. Consider investigating other causes of optic neuropathy if in any doubt about the diagnosis. If LHON is suspected, arrange ECG because of the association with cardiac conduction defects, and genetic screen after counselling. For dominant optic atrophy genetic testing will soon be available but if not use VEP/ERG to confirm optic neuropathy.

Treatment

■Casualty : suggest patients stop smoking and avoid alcohol. Refer to clinic soon if LHON is suspected or routinely if

dominant optic neuropathy with clear family history and longstanding visual loss.

■Clinic : draw the family pedigree (p. 412) and establish the inheritance pattern. Arrange genetic counselling, sightimpaired registration, and low-vision aids as appropriate. Refer to a neurologist if other neurological features are present.

Follow–up Annual review once the diagnosis is established.

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Radiation optic neuropathy

Radiation Optic Neuropathy

Background Radiation to the anterior visual pathways can cause an optic neuropathy months or years after the treatment, but usually within 1–3 years. It is bilateral in 75% of patients. The cumulative radiation dose is usually >2400 cGy with 75% receiving >5000 cGy. Chemotherapy and diabetes increase the risk. The mechanism is likely to be microvascular.

Clinical features Rapid, progressive, painless, visual loss that stabilizes after a few months (<6/60 in 85%, 45% become NPL). There is decreased colour vision, field loss, and an RAPD. The disc is initially normal, then becomes atrophic. Cataracts, and radiation retinopathy that mimics diabetic retinopathy are typical and disc swelling may occur if the eye has been irradiated.

Differential diagnosis Consider recurrence of the primary disease, radiation-induced malignancy, raised intracranial pressure, venous sinus thrombosis, postchiasmal radiation damage, and other optic neuropathies (compressive, demyelinating, traumatic, infiltrative, inflammatory, and nutritional).

Investigations T1 and T2 weighted MRI is normal but optic nerves enhance with contrast for the first few weeks. Arrange a Humphrey 24–2 field test.

Treatment

■Casualty : refer to clinic within 1 month.

■Clinic : arrange imaging and exclude other diagnoses. Arrange low-vision aids, partially sighted/blind registration as appropriate. There is no proven treatment although hyperbaric oxygen is sometimes tried.

Follow–up Review every 2–3 months until the vision stabilizes, then annually.

Optic Nerve Tumours

Background Optic nerve glioma typically develops early in life and 90% are diagnosed by age 20 years. Optic nerve sheath meningioma is unilateral in 95% with a peak incidence in the third to sixth decades and a 4 : 1 female preponderance. Rarely, malignant glioma causes visual loss over several weeks in

adults.

Symptoms Gradual painless loss of vision often described as fogging or dimming. Gaze-evoked amaurosis occurs with optic nerve sheath meningiomas. Sudden visual loss occurs rarely when the tumour bleeds into itself. Children may present with strabismus.

Signs Features include loss of colour vision and VA, any type of visual field loss, disc swelling, optic atrophy or optic disc collateral vessels, particularly with meningiomas. Proptosis and limitation of eye movements may occur from a splinting effect of a large tumour. Tumours may compress the eye and induce hyperopia. Signs are usually unilateral, rarely bilateral, but glioma of the chiasm causes bilateral signs

History and examination Record the duration and progression of symptoms, VA, colour vision, confrontation visual fields, RAPD, eye movements, measure proptosis, dilate and examine optic discs and fundi. Exclude vitritis.

Differential diagnosis Consider optic neuropathy (traumatic, compressive, demyelinating, infiltrative, inflammatory, radiation, nutritional, and toxic) and normal pressure

glaucoma.

Investigations Arrange Humphrey 24–2 field test and imaging:

■Glioma : CT or MRI shows enlargement (classically fusiform) of the nerve with minimal contrast enhancement

(Fig. 14.16).

■Meningioma : fat suppression (STIR) MRI characteristically shows bright enhancement with gadolinium (Fig. 14.17). Calcified psammoma bodies may show up on CT. Diffuse optic nerve thickening is typical with a tram-track sign of enlarged nerve sheath.

Treatment

■Casualty : if available, order an MRI scan and arrange early (4–6 weeks) neuro-ophthalmic follow-up.

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Cerebrovascular disease

Cerebrovascular Disease

Background Disease of the carotid artery can cause monocular visual symptoms. Vertebrobasilar insufficiency can result in recurrent episodes of bilateral, simultaneous, transient visual loss. Occlusion may be due to cardiac emboli and typically affects elderly arteriopaths.

History Record the duration of visual loss and speed of onset. Ask about scintillations, coloured circles, hemianopia, halos, postural hypotension, and symptoms of vertebrobasilar ischaemia (especially loss of balance and dizziness). Assess cardiovascular risk factors including smoking and diabetes.

Examination Record VA, colour vision, confrontation visual fields, RAPD, dilate and check fundus for emboli, disc swelling, and hypertensive changes. Listen for a heart murmur, carotid bruit, and examine the peripheral pulse rate and rhythm, BP lying and standing and in both arms, cranial nerves, and cerebellar function.

Clinical features Consider the following manifestations of cerebrovascular disease and whether urgent onward referral is required.

■Carotid territory:

1.Transient monocular visual loss : see page 634.

2.Ocular ischaemic syndrome : see page 483.

3.Carotid dissection : there may be a history of trauma which may be minor. Features include pain in the neck, jaw or throbbing headache, ipsilateral Horner’s syndrome (32%),

transient visual loss, TIAs (30%), or embolic CVAs (46%). Arrange axial MRI of the neck ± MRA. Anticoagulate for 3 months. Associated with Ehlers-Danlos and Marfan’s syndromes, pseudoxanthoma elasticum, and cystoid medial necrosis.

4.Takayasu’s disease : a rare vasculitis which affects large vessels such as the aorta and carotids. Ocular ischaemic syndrome may result and cases may present to eye clinics.

5.Moya Moya : if carotid occlusion occurs early in life (radiotherapy, idiopathic) collateral vessels develop and ischaemic complications of the abnormal vasculature develop in later life.

6.Giant carotid aneurysm in cavernous sinus : may cause retro-orbital pain and compressive optic neuropathy. The