ST GRAPHICS: MIKE M DIZON

Implant being tried out here does not damage cornea or affect distant vision

A TINY doughnut – less than a tenth the thickness of a sheet of paper – is promising new hope to old eyes.

With age, adults often develop near-vision problems – or what is known in the medical word as presbyopia.

But in a new procedure being tried out by doctors here, a small doughnut-shaped piece of black polymer – less than 4mm wide and very thin – is placed directly in one of the patients’ pupils.

This does not reduce the actual degree of presbyopia. Instead it uses the pinhole principle to increase the eye’s depth of the field – so that near objects that were previously blurred now appear sharper. Think of it in terms of a camera – by making the aperture smaller, images can be brought into sharper focus.

The Singapore National Eye Centre (SNEC) is trying out the new implants on 50 patients here as part of global clinical trials.

The worldwide trials will involve about 400 patients in total, and the SNEC is the only centre in Asia selected to take part.

Preliminary results of tests on some 100 patients in the United States and Europe have shown that patients could see an average of three to four lines lower on a 13-line eye chart after getting the implant.

Currently, besides glasses or contact lenses to help them see near objects, patients can also opt for several surgical procedures, mostly offered by specialists in private practice.

There is conductive keratoplasty, where the shape of the cornea is changed with controlled heat waves, generated by radio frequencies.

Alternatively, patients can opt for a type of Lasik surgery where a laser is used to sculpt the cornea, effectively creating a multi-focal lens on the eye itself.

Then, there is another procedure for patients who have both presbyopia and cataracts. Doctors remove the cloudy eye lens and replace it with a multi-focal lens.

While these methods correct the degree of presbyopia at the time of the operation, they will not work if the patient’s presbyopia worsens, explained Dr Chan Wing Kwong, who heads SNEC’s refractive service. These procedures also tend to worsen a patient’s distant vision and are irreversible.

But the new implant is expected to remain effective even if the patient’s presbyopia worsens, and does not appear to affect the patient’s ability to see faraway images.

It is so tiny that it does not damage the cornea, and can easily be removed, said Professor Donald Tan, deputy director at the SNEC. This means that the patient can “upgrade” to a better implant or other operations in future, if necessary.

Mr Adrian Raj Angappan, 46, who is in between jobs, got his implant last week.

He said he could read newspapers without glasses as early as four days after his operation, and all the lines on the eye chart.

People aged between 45 and 65 who have no other eye conditions apart from presbyopia, or who have perfect vision except for presbyopia after a Lasik or cataract operation, are eligible for the trial.

Those who are interested can call 6322-4500 or 6322-4501.

huichieh@sph.com.sg