Glaucoma is one of the commonest causes of blindness and partial sight in the UK.
There are three types of Glaucoma:
- Acute (closed angle) Glaucoma
- Chronic (open angle) Glaucoma
- Congenital Glaucoma.
Acute Closed Angle Glaucoma
Acute Closed Angle Glaucoma may be primary (not caused by another disease) or secondary (caused by another eye disease)
Primary Acute Glaucoma: aqueous humour (liquid in the eye) cannot drain from the eye due to blockage. This can lead to increase in the internal eye pressure to 50mmHg or more. Normal pressure is 21mmHg or less. The symptoms include painful eye, nausea, blurred vision and seeing coloured light (haloes) around a white light source. In addition to high eye pressure, signs include a fixed semi dilated pupil, a swollen cornea and red eye.
This type of glaucoma is an ocular emergency and the patient is normally referred immediately by the optometrist to the hospital for reduction of pressure by medication, eye drops or surgery. If not treated immediately, this glaucoma causes blindness due to damage to the optic nerves.
Secondary Acute Glaucoma: occurs as a result of another eye disease e.g.iritis- inflammation of the iris when sticky cells leak into the anterior chamber. Signs and symptoms are similar to the primary.
Chronic Open Angle Glaucoma
This is more common then acute affecting 1-2% of the population. It is more often detected in people over 40yrs old. However, it can occur in younger people and even children. Unfortunately there are no symptoms until the very late stages of the disease, so without a regular eye examination, sufferers do not know they have it. The increase in pressure is gradual slowly damaging the nerve fibres of the optic nerve. Only in the late stages of disease, when most of the nerve fibres have been damaged would you notice “tunnel vision”. The peripheral field of vision is lost and only a small central area of clear vision remains.
The devastating effects of glaucoma make early detection important. There are various signs the optometrist will look for. They consider the internal eye pressure, look for any damage to the nerves using an ophthalmoscope and test for visual field defects.