Monday, September 28, 2009

Beware of premature cornea ageing

A pair of contact lenses, positioned with the ...Image via Wikipedia


Neo Chai Chin

HERE's one more thing for contact lens wearers to be wary of - your corneas may be prematurely ageing.

Wearing contact lenses with low oxygen permeability for prolonged periods can damage the cornea, a transparent layer covering the eye. And the majority of Asians are using such lenses, said Australian eyecare expert Professor Brien Holden (picture).

This, in turn, may cause conditions like dry eyes, and cause the corneas to look "older" than normal. A sign of the latter is when the cells on the innermost layer of the cornea become varied in size - a condition called polymegethism, which is closely associated with corneal exhaustion syndrome, said Prof Holden of the University of New South Wales.

Cell density decreases with age, but studies have shown that a lack of oxygen accelerates the process. When that happens, a person may then have to cease wearing contact lenses altogether, he said.

Prof Holden, who is also chief executive of the Institute for Eye Research, an Australian company, was in Singapore yesterday.

"The first thing to do is to consult your local optometrist or ophthalmologist and talk to them about whether you are showing signs of excessive redness of the eye associated with low oxygen of your lenses, " he told Channel NewsAsia.

However, the "simplest thing" is to wear high oxygen permeable contact lenses or silicon hydrogel lenses, he said.

Singaporeans, it seems, are already making the switch.

Optometrists told Today of a rapid uptake since silicon hydrogel lenses became readily available four years ago.

President of the Singapore Optometric Association David Chong said over half his customers are using them. For optometrist Dr Koh Liang Hwee, the number is three in 10 monthly disposable lens users, and nine in 10 bi-weekly disposable lens users.

Silicone hydrogel lenses cost about 20 per cent more than regular soft lenses, they said.

To spread awareness, contact lens manufacturer Ciba Vision is launching a premature corneal ageing campaign this month.

A better alternative however, is to avoid wearing contact lenses altogether, said Dr Ray Manotosh of the Department of Opthalmology at the National University Hospital (corrected at 3:15PM, Sep 1).

"Contact lenses have many side effects (including) infection related to hygiene, and bacterial infection where you can lose your eyesight," he said.

Dr Manotosh added that compared with hard lenses (usually worn on doctor's prescription), the incidence of polymegethism among soft lens wearers is low.

But for those who insist on wearing contact lenses, "silicon hydrogels are the better lens, and the preferred lens should be those for daily wear instead of weekly or bi-weekly wear", he said.

From TODAY, Health – Tuesday, 01-Sep-2009