Vision Disorders

SHORT-SIGHTEDNESS - MYOPIA :: FAR-SIGHTEDNESS - HYPEROPIA
ASTIGMATISM :: PRESBYOPIA :: MONOVISION

People with visual errors often aren't aware of the type of condition they have. Many terms can be quite confusing and we would like to explain the differences when vision is not normal.

An estimated 9.7 million Australians have a visual error that means glasses, contact lenses or surgical treatment. Many are not aware of the type of condition they have. Medical terminology can be quite confusing so it is important that we explain the reasons for the differences.

SHORT-SIGHTEDNESS - MYOPIA

This means you have trouble seeing in the distance but usually you can see things close up. With myopia the cornea and the lens of the eye are too strong for the length of the eye, causing light rays to focus in front of the retina making, images blurred once they reach the retina at the back of the eye when looking at things at a distance.

FAR-SIGHTEDNESS - HYPEROPIA

This means you can see things in the distance better but have more trouble focusing clearly on things up close, particularly as you get older. In far sightedness, the lens is often too weak, making the eye muscles compensate by putting extra focus to the natural eye lens.

ASTIGMATISM

Astigmatism occurs when your cornea is shaped like an oval football rather than a round soccer ball. Whilst no-one has a perfectly-shaped cornea, astigmatism can range from slight to significant. If the curvature is strong, the light is not focused at two different locations, therefore blurred. It is possible to have this condition by itself, or combined with short-sightedness and far-sightedness.

PRESBYOPIA - (Natural ageing)

Presbyopia is a gradual loss of the ability to focus on near objects. It usually begins around the age of 45. The natural lens in younger eyes is soft and can change shape when focusing on near images. As we age, the natural lens becomes harder and looses its ability to focus. Most people will notice the onset of presbyopia by moving images further away from their normal position of reading. It is at this time that we start to wear reading glasses. Problems related to natural ageing of the eye can be treated with a process called monovision (see next section).

MONOVISION

A technique called monovision - or blended vision - can be offered to people undergoing refractive correction. Monovision is where one eye is focused for up-close vision and one for distant vision. Although most people adapt very well to monovision, sometimes it is not suitable. This particular treatment is only required for those who are presbyopic. Monovision is an unusual concept and does take a little getting used to. We will determine if it is a suitable option for you, with a contact lens (or lenses), to demonstrate your probable outcome. A point to remember is that even if you have a monovision procedure, you may still need to wear reading glasses for small and fine print.

Monovision can affect your depth perception slightly. The alternative to monovision is bilateral (both eyes) normally sighted for distance (emmetropia), but if you are presbyopic you will most certainly need a pair of reading glasses for close reading work such as computers or newspapers.