A group of disorders of the eye characterised by the intraocular pressure being so high as to damage the nerve fibres in the retina and the optic nerve (see EYE) as it leaves the eye en route to the brain. The affected person suffers limitation of the field of vision and on examination the optic disc can be seen to be cupped. The clinical signs depend on the rate and extent of rise in pressure.
Individuals most at risk have a family history of GLAUCOMA (especially among siblings), are myopic (short-sighted), or have diabetic or thyroid eye disease. People with a strong family history of the disease should have regular eye checks, including tonometry, from the age of 35 years.
Glaucoma is usually classified as being either open-angle glaucoma or narrow-angle glaucoma.
is a chronic, slowly progressive, usually bilateral disorder. It occurs in one in 200 people over 40 and accounts for 20 per cent of those registered blind in Great Britain. Symptoms are virtually non-existent until well into the disease, when the patient may experience visual problems. It is not painful. The characteristic findings are that the intraocular pressure is raised (normal pressure is up to 21 mm Hg) causing cupping of the optic disc and a glaucomatous visual-field loss. The angle between the iris and the cornea remains open. Treatment is aimed at decreasing the intraocular pressure initially by drops, tablets and intravenous drug administration. Surgery may be required later. A trabeculectomy is an operation to create a channel through which fluid can drain from the eye in a controlled fashion in order to bring the pressure down.
affects one in 1,000 people over 40 years of age and is more common in women. Symptoms may start with coloured haloes around street lights at night. These may then be followed by rapid onset of severe pain in and around the eye accompanied by a rapid fall in vision. One eye is usually affected first; this alerts the surgeon so that action can be taken to prevent a similar attack in the other eye. Acute narrow-angle glaucoma occurs because the peripheral iris is pushed against the back of the cornea. This closes off the angle between iris and cornea through which aqueous humour drains out of the eye. Since the aqueous humour cannot drain away, it builds up inside the eye causing a rapid increase in pressure.
Treatment consists of regularly using eye drops as variously tailored combinations of prostaglandin analogues, a BETA BLOCKER, alpha agonists or a carbonic anhydrase inhibitor.
Various types of LASER treatment – trabeculoplasty (‘burning’ the trabecular network); iridotomy (cutting holes to relieve pressure); and ciliary-body ablation by ‘burning’ – are sometimes used in preference to surgery.