By Dr Y.L.M.

MY father has diabetes. Recently, the doctor discovered something in his eye and told him he might soon be experiencing difficulty in seeing. I am worried he might go blind. Does blindness mean not being to be able to see anything at all? Or would he be able to make out some shapes?

Your father is likely to be suffering from diabetic retinopathy, one of the complications of diabetes mellitus. And yes, one of the consequences of diabetic retinopathy is blindness.

The most advanced stage of diabetic retinopathy is the advanced proliferative stage, when new blood vessels rupture, causing further scar formation. The scar tissue can then pull the retina away from its normal position at the back of the eye.

Unlike what most people expect, blindness does not denote "complete" blindness only, which means the total absence of visual perception. Only 10 per cent of people who are legally classified as "blind" are fully blind.

The term "blindness" also applies to partial visual impairment. Legal blindness is categorised as having a visual acuity of 20/200 or less in your better eye (the eye which can see better between the two) when you are having the best correction (eyeglasses or contacts) possible.

Normal vision is 20/20, by the way. Many short-sighted people can achieve this or almost achieve this by wearing glasses, or wearing contact lenses.

A visual acuity of 20/200 means that you will have to stand at 20 feet from an object to see with the same degree of sharpness as a normal person standing 200 feet away.

Before you raise your hand and say, "That's me!", remember, this has to be AFTER best visual correction, or in other words, the thickest glasses money can buy.

Just below the level of blindness is the term "low visual acuity".

My aunt used to tell me blindness is a disease of old age. She says the more we use our eyes to do close work, such as reading and sewing, the faster we can become blind. For a long while, she made me frightened to read!

Myopia or short-sightedness has a strong genetic component to it, though close reading, doing too much computer work and other close work often exacerbates it.

It would not be exactly accurate to say that blindness is a disease of old age because old age per se does not cause it.

This means that when you grow old, you will not automatically get blind. But with old age comes many disorders like cataract, macular degeneration and diabetic retinopathy.

It is true to say that blindness occurs most often with old age because of these disorders.

Half of all blind people are over the age of 65.

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