Compensatory Lenses

Glasses can sometimes be prescribed for other reasons apart from correcting eyesight.

Sometimes schoolchildren who have normal eyesight still get eyestrain at school or when reading.

Sometimes in these cases they will benefit from glasses to take the strain off their eyes. Such glasses help compensate for focussing or eye coordination issues which are contributing towards their eyestrain. Wearing such glasses can therefore improve reading and school performance.

The focussing problems can be related to the ability to maintain focus at near otherwise known as ‘amplitude of accommodation’ or ‘accommodative lag’.

A reduced ‘amplitude of accommodation’ results in what is called an ‘accommodative insufficiency’, literally not having enough focussing power and glasses can be prescribed to compensate for this.

Similarly, not being able to sustain focus at near can lead to what is called ‘accommodative lag’ and again glasses can be prescribed to compensate.

Another aspect of focussing is ‘accommodative facility’ which is the ability to alter focus from one distance to another. Commonly, when this ability is reduced the eyes take a while to focus from the board to your work and back again. Copying from the board becomes a challenge and can also be slow.

Glasses can be prescribed in all of these cases as long as reading ability or focussing ability improves when the glasses are worn. If the glasses do not make a perceivable difference the child is not necessarily going to wear them.

Please note that in all the above cases, that the eyesight is normal. However, the child will not be functioning to the best of their ability because of this subtle focussing problem.

Wearing the glasses will result in faster focussing to and from the board at school so improving the ability to copy. The glasses may also make focussing at near more comfortable so making reading and close work easier.

Why has the focussing and eye coordination altered from normal? Usually because the child has started reading or using hand held electronic devices for too long without taking breaks. The muscles that control the focussing could be said to have started to ‘cramp’ so using the glasses allows these muscles to relax and allow the child’s eyes to function better.

The good news is that the use of compensatory glasses is usually temporary as long as they are worn as suggested and measures are followed to take appropriate breaks to relax the eyes with close work (see ‘visual hygiene’ advice sheet in ‘downloads section’).