What is Astigmatism?

Astigmatism is an error in the eye that prevents rays of light from focusing together on the retina. This happens when the cornea is unequally curved in different directions. Instead of being globular, the curvature of the eye becomes egg shaped, longer in one axis than the other. This condition means that objects seem distorted and out of place. A ball for instance would look like an egg. Spectacles can correct astigmatism. You will know if you have this condition if there is a figure in the cylinder box on your prescription. (See 'what does my prescription mean?')

What is Myopia?

Myopia means short sightedness. If your eyes are myopic, objects that are far away appear blurred and only near objects can be seen clearly. The worse the myopia, the closer the object has to be placed for clarity. Myopia is inherited, and is usually due to the eyeball being longer than normal. Spectacles or contact lenses are needed to alter the focus and allow distance vision. Short sightedness can also be linked with old age.

What is Hypermetropia?

Hypermetropia means long sightedness. Young people with hypermetropia can see clearly without spectacles both in the distance and for reading, but with increasing age, the long-sighted person may need spectacles for both distances. The muscles in the eye become less active, and it becomes more difficult to alter the focus. When this happens, it can be a shock to middle-aged long-sighted people who have always had excellent distance vision and are abruptly faced with needing glasses for both distance and reading.

What is Presbyopia?

This condition occurs with increasing age as the ciliary muscle weakens and the lens hardens. To understand presbyopia, you need to know about your eye's near point. This is the closest position that you can hold a book and still see it clearly. In children or short-sighted (myopic) people, this can be a little as 3-4 inches (8-10 cm). If you have presbyopia, you will notice that your near point moves further away and you have to push books further and further away to read properly, while your head is held back. Eventually, when the near point reaches beyond arms length, spectacles are needed. This condition happens gradually and at first you might only need to hold a book in a brighter light to see clearly. Usually by the age of forty, however, glasses are needed.

Has anyone invented a pill that can help eyesight?

Scientists have begun development and testing of a drug that they hope will keep children's vision from deteriorating. An anti-myopia pill could be just a few years away! Further Reading: The many facets of the myopic eye; a review of genetic and environmental factors. By Jane Gwiazda and Lynn Marran. Look for this on www.amazon.co.uk

Want to know more about eyes?

How the eye works
Eye diseases
Optical illusions
Myths about eyes and vision