Other Eye Diseases

Cataracts

Cataracts are the most common cause of blindness in the world. The condition manifests as gradual, painless loss deterioration of vision. Risk factors include:

• Age: the most important risk factor
• Metabolic: diabetes, galactossaemia, Wilson's disease, hypocalcaemia
• Drugs: steroids
• Traumatic
• Inflammatory: uveitis
• Down's syndrome

Investigation is targeted towards secondary causes. such as those listed above. Treatment is extraction of the cataract with insertion of an intraocular lens, a procedure which is termed phaecoemulsification

Glaucoma

This is increased pressure in the eye causing optic nerve damage. The "cup" of the optic disc is the central region where there are no nerves, hence when damage occurs ("cupping") the cup enlarges, which is seen on ophthalmic inspection as a thin neuroretinal rim.

There are 2 types of glaucoma:

Open Angle (Chronic)

This is the commonest type. It arises due to reduced outflow of aqueous humour through the Canal of Schlemm. Risk factors include: age, family history, myopia, and being black. The condition manifests as gradual painless loss of the peripheral visual field (an arcuate scotoma), whilst the central vision remains intact.

Investigations include aplenation tonometry (which measures intraocular pressure), and visual field testing. The treatment is to reduce the pressure using:

1. Drugs: topical beta blockers, topical prostaglandin analogues (latanoprost), carbonic anhydrase inhibitors (acetazolamide).
2. Surgery

Closed Angle (Acute)

This is an emergency. a sudden increase in pressure arises when reduced drainage of fluid occurs, due to an ageing lens pushing the iris forward against the trabecular meshwork. The clinical features are: a sudden "aching" painful red eye, nausea, vomiting, headache, and severe ocular pain. Patients might see "halos" with a rainbow pattern around lights. The pupil is fixed and dilated. Risk factors include age, hypermetropia, women. Unlike closed angle glaucoma the condition is not familial.

The treatment is:

1. Prompt treatment to preserve sight: acetazolamide and pilocarpine (which constricts the eye, improving drainage).
2. Definitive surgical treatment, which involves making a hole in the periphery of the iris of both eyes.

Temporal Arteritis

This is a systemic vasculitis. Because of its potential to cause irreversible blindness, it is an ophthalmological emergency.

The disease is an inflammatory granulomatous arteritis of large arteries associated with polymyalgia rheumatica. The visual loss occurs due o arterial inflammation and occlusion. Clinical features include a severe headache, tenderness of the scalp, claudication of the jaw which is worse on eating, and "coming and going" vision. Symptoms of the associated polymyalgia rheumatica include sudden onset pain and stiffness of the the shoulders/neck, and hips/lumbar spine.

Investigations revealed raised ESR and CRP. A temporal artery biopsy should be performed, which reveals intimal hypertrophy, giant cells, and inflammatory infiltrate. The biopsy may, however, miss focal lesions and sometimes repeats are required. Treatment is immediate high dose prednisolone on clinical grounds. The dose is reduced after a few months

Macular Degeneration

This causes loss of visual acuity.

Non-exudative

Drusen are seen on ophthalmoscopy. These are variably sized white or yellow spots scattered throughout the macula.

Exudative

This has the worst prognosis. Neovascularisation and leakage of serous fluid or blood occurs. Retinal detachment is a complication.

Retinal Vein Occlusion

This is sudden unilateral painless loss of vision that often occurs on waking. The retinal veins are engorged, flame shaped retinal haemorrhages and cotton wool spots are seen. The optic disc is swollen. Risk factors include diabetes, hypertension and glaucoma.