presbyopia

The lens in the eye is built up in layers, like an onion. New layers are constantly being added to the outside, compressing and hardening those in the centre. This results in a gradual stiffening of the lens over time. The ciliary muscle grows stronger to compensate for this, doubling in size between the ages of 20 and 40. Unfortunately, as we do our close work in relatively poor light with enlarged pupils, the eye is unable to focus as well as it might and the ciliary muscle does not get as much exercise as it needs. The growth of the ciliary muscle falls behind what is required for the closest focusing. This ‘near point’ gradually moves further away until by the mid-40s it starts to interfere with reading small print. This is called presbyopia. The conventional treatment for presbyopia is to place a lens in front of the eye to add the extra focusing power that the eye is unable to provide. This immediately brings print into focus but also leaves the ciliary muscle less work to do. With habitual use of reading glasses the ciliary muscle gets less exercise and starts to get weaker, further reducing the ability to focus close up.

What to do about Presbyopia

The ciliary muscle needs more exercise rather than less. It is not under conscious control so we have to find a way of encouraging the eye to focus itself more fully. The answer is to provide an artificially small pupil (a pinhole) in front of the eye, to help the focusing system work more fully. This is the principle behind Trayner pinhole glasses. These have an array of small holes through black screens that replace the lenses in a pair of glasses. By reading with the aid of Trayner pinhole glasses for fifteen minutes or so every day, the ciliary muscle is exercised and grows stronger. Vision is clearer while using Trayner pinhole glasses because the ciliary muscle and lens are focusing beyond their habitual range. The unaided vision improves gradually over a few weeks as the muscle gets stronger with the extra use.©Peter Duthie 1998/2000