Glaucoma

Description

A group of conditions in which there is a characteristic appearance of damage to the optic nerve as it leaves the eye (cupping) and corresponding defects in peripheral vision. In most cases the pressure within the eye (intra-ocular pressure: IOP) is sufficiently elevated to cause damage to the nerve either directly or by causing impairment of its blood supply. However damage may occur even with a normal pressure in some patients (normal tension glaucoma).

Glaucoma is generally a slowly progressive condition (chronic glaucoma) though sudden rises in IOP occasionally occur (acute glaucoma). Glaucoma is further divided as to whether the tissues that drain fluid from the eye are open (open angle) or closed (closed angle). Glaucoma may also occur as a result of other diseases either within the eye or beyond (secondary glaucoma) and very rarely is congenital (at birth or shortly afterwards). The majority of patients with glaucoma in the UK have chronic open angle glaucoma, also called primary open angle glaucoma or chronic simple glaucoma.

The cause of the primary glaucomas is not clear. There is a strong genetic tendency. The risk of glaucoma increases progressively with age with 1.6% of those >40 years but 4% of those >80 years affected. It is also more common in patients with severe myopia, diabetes and hypertension.

Clinical Features

Chronic glaucoma is usually without symptoms until it has caused a significant loss of the visual field. Very high pressures occasionally cause discomfort, headache or blurring of vision with haloes, but these features are normally seen as a result of a sudden rise in intra-ocular pressure from acute glaucoma when there may be associated feelings of being unwell, nausea and vomiting. The eye also becomes inflamed and the pupil enlarged and unreactive to light.

Secondary glaucomas may be associated with previous trauma, inflammation (eg uveitis), retinal vein occlusion (rubeotic glaucoma), steroid eye drop treatment, abnormalities of the tissues within the eye (eg Pseudo-exfoliation, or pigment dispersion syndrome, tumours, displaced or dislocated lens), or pressure on the eye from outside as in thyroid eye disease or carotid-cavernous fistula.

Congenital glaucomas are very rare. The initially normal eye may enlarge and the cornea become cloudy or there may be visible structural abnormalities in the cornea or iris that lead on to glaucoma (eg aniridia).

Management

Screening by an optometrist is recommended every other year from age 40 or younger if there is a first degree relative with glaucoma.

Acute glaucoma requires immediate transfer to an eye department for treatment.