Vista Eyes - Laser Eye Clinic

If light does not focus directly on the retina, the eye will be either near-sighted, far-sighted or astigmatic depending on the location of that focus. These problems are called refractive errors.

In the normal eye, light is focussed through the cornea and lens onto the retina. Here the light is converted into electrical signals, which are sent to the brain to enable sight.

Short-sightedness occurs when the cornea is too steep or the eyeball is too long. This causes light to be focussed in the front of the retina, making it difficult to focus over longer distances.

Long-sightedness (Hyperopia)

Long-sightedness occurs when the cornea is too flat or the eyeball is too short. Light is focussed behind the retina, which makes it difficult to focus up close. In older age groups, it's difficult to focus on anything at all.

When curvature occurs across the cornea, light is focussed on multiple points away from the retina rather than on a single point. This is known as astigmatism. People with this condition are often described as having corneas shaped more like a football than a soccer ball. Astigmatism can occur in association with short- and long-sightedness, and it can make it difficult to focus on anything at all.

As people age, the lens within the eye becomes harder and rounder. This makes it more difficult to change the focus of the eye from distant to close objects. For most people this means they need to wear reading or multifocal glasses as they proceed into their forties.

Keratoconus is a progressive eye disease, which causes a thinning of the cornea, the clear front surface of the eye. This thinning causes the cornea to lose its natural shape leading to distortion of vision. As the disease progresses, the quality of one's vision deteriorates. Keratoconus affects about 1 in 2000 people and tends to affect people in their late teens and can progress through their 20s and 30s.

The lens within the eye becomes less and less clear as you get older. Because of natural deterioration of the proteins within the lens, what was once clear tissue becomes more like frosted glass or a dirty windscreen. This is part of the aging process. The cloudy lens is called a cataract. Light becomes scattered by the cataract and can no longer reach the back of the eye as effectively.