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The truth about pinhole glasses

A pair of glasses which can permanently improve eyesight rather than just correct it may sound like the stuff of dreams. But this is the promise being made for "pinhole" glasses - they look like sunglasses covered with a grid of tiny holes - by their manufacturer, a company in Somerset. Wearing the glasses for 15-20 minutes a day, it claims, can lead to noticeable improvements in vision.

The glasses can apparently also help relieve VDU eye strain, fatigue and headaches - and all for the price of pounds 25 a pair.

These claims were recently given a splash in one particular tabloid, with the result that the company's lines are constantly engaged by eager potential purchasers. They are, however, strongly disputed by the College of Optometrists which says they are unsubstantiated and should be viewed "with a great deal of caution".

So who is right? There's no doubt that while they are being worn, pinhole glasses make for a clearer image for those with vision defects, similar to the effect of screwing up the eyes. They do this by artificially making the pupils smaller and reducing the amount of light getting through.

The "pinhole effect" has been known about for centuries and pinhole glasses are used by optometrists (who are qualified to examine vision) as a sight aid where conventional glasses cannot help - in the case of a scarred cornea, for example. But they are not normally used where prescription glasses can be used, because they cut down on light, and cannot give as clear an image.

The manufacturer, Trayner Pinhole Glasses, argues that its product has a more permanent effect than this. It says that while normal glasses encourage the eye to become lazy, the pinhole type encourage the ciliary muscles to become stronger, pulling the lens into the correct shape. This is based on the view that the eye can be made to adapt to its environment and can be encouraged to change shape towards normal. Improvements can be made, it is claimed, within a few weeks in the case of those who use reading glasses (where the lens is too stiff rather than the wrong shape), and within a few months in the case of those with distance lenses.

The traditional view, however, is that poor sight is for the most part genetic, and is caused by the eye being too short (in the case of long- sightedness) or too long (in short-sightedness), so that the image is focused either behind or in front of the retina. Optometrists say there is little evidence that muscle exercises of any kind will help poor sight, which can only be put right by prescription glasses.

What is certain is that so far, there have been no published clinical trials of the effect of pinhole glasses on permanent vision. The College of Optometrists points out that the company has been "pressed for scientific validation of its claims" but that clinical trials which were arranged "were not pursued to their conclusion". The company's director, Peter Duthie (whose own background is electronic engineering), admits that all his evidence is so far anecdotal but retorts that optometrists have been reluctant to carry out the trials which under current legislation he cannot conduct himself.

This is not the first time that pinhole glasses have been marketed in Britain. In 1992, Birmingham City Council won a case under the Trade Descriptions Act (1968) against a manufacturer making claims about the health benefits of pinhole glasses. In 1993 the Advertising Standards Authority upheld a complaint about claims that by wearing pinhole glasses, people could give up wearing conventional glasses.

Certainly there is no substitute for having the eye examined to detect problems in eyesight and eye disease; self-diagnosis is inadvisable. The College of Optometrists also says that walking round while wearing pinhole glasses in normal lighting conditions could be dangerous and wearing them while driving even more so.

Cherrill Hicks