Sept 22 - IF you're a baby boomer who has been getting excited over news of presbyopic lasik, don't chuck away your reading glasses yet.

That's because trying to perform lasik to correct presbyopia in the ageing eye is like chasing a moving target, as the degree of presbyopia will increase as one grows older.

'I call presbyopia the 'mid-life crisis' of sight. It is as inevitable as your income tax, and will start hitting you when you turn 40-45 years of age,' says Dr Lee Hung Ming, senior consultant ophthalmologist and medical director of Parkway Eye Centre at Gleneagles Hospital, about presbyopic lasik.

Presybopia, or 'old sight', is the age-related difficulty in accommodating the eye to near-vision. Doctors do not really recommend lasik surgery for it because the effects might last only for a few years before the old-sightedness goes up again. 'Presbyopic lasik attempts to correct old-sightedness on aged eyes, but it's not completely possible yet,' says associate professor Heng Wee Jin (above), head of Cornea and Refractive Surgery of The Eye Institute, National Healthcare Group and senior consultant at Tan Tock Seng Hospital.

For now, there are two ways of treating presbyopia with lasik. One is with presbyopic lasik and the other is monovision lasik, explains Dr Lee. What presbyopic lasik does is that instead of simply flattening the cornea, the laser creates a multi-focal cornea giving only fair vision for far and for near. In addition, patients may have to put up with glares and haloes after operation.

For someone who wants to cheat nature, monovision lasik sees the degree of shortsightedness fully treated by lasik on the dominant eye, while leaving the weaker eye off by about 100 degrees, to compensate for near vision.

'But the problem is that not everyone can get used to it. Only about 40 to 50 per cent of the people get used to correction like this,' says Dr Lee. 'We call it the plasticity of the brain. Women can apparently adapt better,' he adds.

The best thing for a baby boomer to do is probably to try out monovision spectacles first to see if they can get used to it, before asking for monovision lasik for their eyes.

Assoc Prof Heng warns: 'Some people may not be able to get used to the imbalance in vision. For professionals or technical people who depend a great deal on sight, they may not be able to function well with monovision. Again, it's a compromise, and reading glasses is probably a more optimal solution'.