Glaucoma is a group of conditions but broadly speaking can be divided into chronic open angle glaucoma (COAG) and closed angle or acute glaucoma.
COAG is the commonest form of glaucoma and affects 1-2% of the population over 40 years of age. Fluid produced inside the eye gradually builds up as its drainage route slowly blocks up. Slowly, over months and years, the intra-ocular pressure (IOP) rises and gradually damages the optic nerve. Because the peripheral vision is affected first sufferers are unlikely to be aware until the condition is quite advanced, and as the damage is permanent, it is important to detect COAG early.
Who is at risk?
Anyone over 40 should have a routine eye examination every 2 years or so; the optometrist is well trained to spot the signs of glaucoma. However, people in the following groups are at a slightly higher risk of developing COAG:
• People, especially those over 40 years, with an immediate relative suffering from COAG.
• Afro-Caribbeans over 25 years
• People with diabetes
• Short-sighted people (myopes) over -6.00 dioptres
• Persons over 80 years of age
How is COAG detected?
Most cases are picked up at a routine eye examination, although the diagnosis of early glaucoma is not always easy. It is usually made on the basis of optic nerve appearance (see OCT below), measurement of the intra-ocular pressure, and assessment of the peripheral vision (a visual field test). Results are not always conclusive and the optometrist may follow glaucoma suspects up at 6 or 12 monthly intervals before referring for specialist advice.
The situation can be complicated because many people have high intra-ocular pressure but don’t go on to develop glaucoma. These people are known as ocular hypertensive and need to be followed up carefully as about one third of them will develop glaucoma.
Equally, a significant number of people develop glaucoma without the pressure ever rising above normal limits which can make detection more difficult. This condition is known as normal pressure glaucoma.
How is COAG treated?
Treatment is generally with eyedrops, which are usually very effective and have minimal side-effects. COAG cannot be ‘cured’ so the treatment is for life, and patients are followed up at intervals in hospital outpatients. In a small number of cases where drops are not effective a minor eye operation may be necessary.
Optical Coherence Tomography (OCT) and Digital Retinal Imaging
Glaucoma will cause visible damage to the optic nerve head over time, although these changes can be very subtle making them difficult to detect. A useful tool in the detection of glaucoma is a digital retinal camera allowing us to photo-document the optic nerve and make comparisons over time. More recently OCT allows us to scan the optic nerve and retina in remarkable detail, providing objective information about the health of the eye; this might allow diagnosis of glaucoma up to 5-7 years earlier than conventional tests. We would strongly recommend OCT analysis to all patients at risk of glaucoma.
These procedures are not available on the NHS and therefore a charge will be made. Please ask about our full glaucoma assessment.