Glaucoma is the most common cause of irreversible blindness in Singapore (Cataract, which is common, can be treated very effectively with surgery). It results in 34% of all blindness in Singapore. Even though the disease affects 3% of those above 50 years old, many Singaporeans have not had their eyes screened for the disease.
Glaucoma is a group of disorders characterised by optic neuropathy (a problem of the nerve which is responsible for vision-the optic nerve), which is due to inappropriately high/abnormally elevated intra-ocular pressure. Once this threshold is crossed, the high intra-ocular pressure causes damage to the optic nerve, resulting in a loss of visual field (the blackened areas represent areas of visual field loss). The threshold beyond which the pressure is considered inappropriately high varies from individual to individual, to take into account factors such as the variation in thickness of the cornea among different individuals, unlike in the past, where pressures of 21mmHg or more were considered inappropriate. Hence, the subtype known as low tension glaucoma, where even as the pressure is less than 20mmHg, there is visible evidence of optic nerve damage on clinical examination and demonstrable visual field losses on visual field testing.
As such, to rule out glaucoma, patients should have their intra-ocular pressures ascertained, their optic nerves examined by an eye specialist, and when indicated, further tests such as visual field examination and pachymetry (measurement of the thickness of the cornea)
Essentially, there are two main types of glaucoma (other than the rarer, occasional patent with the above mentioned low tension glaucoma) viz. Open Angle and Close Angle Glaucoma (the angle refers to that formed between the cornea and the iris).
The open-angle variety accounts for the bulk of glaucoma sufferers. Yet it is difficult to detect because the condition is often asymptomatic. Affected patients may only start to detect changes when it is too late. Peripheral vision is lost gradually and central vision remains till the end, resulting often in patients seeking consultation only when it is too late.
The closed-angle variety presents more acutely, with a rapid spike in the intra-ocular pressure, resulting in patients experiencing eye pain and a quick deterioration in vision. The closed angle type of glaucoma has been found to be especially common among the Chinese, with the elderly having a higher risk for the condition. Laser treatment has a role in preventing attacks of close-angle glaucoma.
In conclusion, it is important to screen for glaucoma especially since the condition affects 10% of Singaporeans > 70 years old, and the condition may affect more than one member of a family. As such, all first degree relatives of the afflicted (such as brothers, sisters, children etc), should have their eyes examined.
If detected early, further loss of vision can be prevented with eye drops. Only a small proportion of patients would ever need laser treatment and an even smaller group would have to undergo surgery (only when all else has failed). This makes it very worthwhile to screen early for the disease.