Short sight, long sight and astigmatism

Short sight, also known as myopia, occurs when your eyes cannot focus clearly on objects in the distance. You can be short-sighted if your cornea is too curved, or if your eyeball is too long. When this happens, light rays coming into the eye focus slightly in front of your retina rather than directly on it as they should.

Otherwise, your eye is perfectly normal but when you try to focus on objects in the distance, they appear blurred. Several factors increase your chances of developing short sight:

• Family history: it is common for several family members to be short-sighted.
• Premature birth: premature babies who are underweight at birth are more likely to be short-sighted when they reach early childhood.
• Ethnic background: researchers have found that certain ethnic groups are more susceptible to short sight than others. For example, more people of Asian origin are short-sighted than those of European origin.

Also known as hypermetropia, long sight affects the way you see objects in close range. People who suffer from long sight are usually able to see objects in the distance clearly, but not those nearby. You can be long-sighted if your eyeball is too short or your cornea too flat in curvature.

These defects cause light rays to focus just behind the retina, so it is fairly easy to see objects quite some distance away, but objects at less than arms’ length are blurred. This is usually a result of genetics. If others in your family have it, you are more likely to develop long-sightedness.

It is possible for anyone to be long-sighted at any age, but it is almost inevitable that you become more long-sighted as you get older. Age related long-sightedness is called presbyopia and it develops in most people in their mid to late 40s. It is not a disease but a result of natural ageing in which the lens inside the eye becomes less flexible.

With age, the eye lens becomes less flexible and loses its ability to focus properly. This normally happens in people as they reach their mid 40s, when they develop long-sightedness.

One of the earliest signs is only being able to read things by holding them at arms’ length. Everybody experiences loss of near focusing power as they age although some people will notice it more than others. Presbyopia develops whether or not you have had laser eye surgery before your 40s for short or long-sightedness.

As the effects of presbyopia continue to affect your lens, you will need regular eye tests to make sure that your glasses or lens provide presbyopic correction to allow you to see objects near to you clearly.