Eye Focus Problems

In myopia light is focused in front of the retina.

Usually this is because the eye is too long. For myopic people (myopes) the distance vision is blurred, but the near vision is often good.

The other common cause of myopia is cataract. With the common type of age-related cataract (nuclear sclerosis) the centre of the lens becomes more dense, and this makes the lens more powerful. Then the light is focussed too quickly, and it comes to a focus in front of the retina.

This is why some people with cataract find that they can read without their reading glasses. Of course, as the cataract (clouding of the lens) becomes more dense, this ability to read without spectacles is lost.

This is the opposite of myopia. Instead of light focussing in front of the retina, the light hits the retina before it has come to a focus. This is because the focussing system of the eye is too weak, or the eye is too short. Hypermetropic people cannot see clearly for near or for distance without some sort of optical correction.

Most short-sight and long-sight can be corrected with spectacles or contact lenses, but many people choose to have it corrected surgically. Broadly-speaking, there are two types of surgery for this: Laser surgery on the cornea (front of the eye), and surgery to replace the lens with a new lens (an implant).

The best option for you depends on a number of factors such as your age, your spectacle prescription, and your visual requirements. If you are starting to develop cataract (clouding of the lens coming with age), then almost certainly lens replacement surgery will be the best option.

At Midland Eye the full range of surgical treatment is available, from customised excimer laser corneal treatment to state-of-the-art femto-second laser-assisted lens surgery with multifocal implants.

Your eye focuses light using two structures: The cornea, which is the clear ‘window’ at the front of the eye; and the lens, which is inside the eye. The cornea actually does most of the focusing.

If the cornea has a regular curved shape, like a football, then the light is focussed well. But if the cornea has an irregular curve, like a rugby ball, then the light is focussed unevenly, which makes the vision less good. This is astigmatism.

Most people have astigmatism but it varies from one person to another. The more your cornea is shaped like a rugby ball, the more astigmatism you will have and the worse your vision. Occasionally, astigmatism can be caused by other factors, such as abnormalities of the lens, or problems from a lens implant.

Astigmatism is often more difficult to treat than myopia or hypermetropia. At Midland Eye we have the full range of possible treatments, from excimer laser or surgical keratotomy to change the shape of the cornea (i.e. to make it less ‘rugby-ball’ shaped), to toric implants (lens implants with an astigmatic correction).

Should you have cataract surgery carried out at Midland Eye, we will usually try to reduce your astigmatism as much as possible to give a better visual outcome.

Throughout your life the lens inside your eye continues to grow (just as your hair and nails do!). This causes the lens to become more and more stiff. The lens has to change its shape for you to change the focus of your eye. As the lens becomes more stiff, it becomes more difficult to focus for near (e.g. reading).

Usually, if you are not myopic (short-sighted), you will find that by your mid 40s you can no longer focus at normal reading-distance. You will find yourself holding the reading matter at arm-length to try to read it. But the lens continues to grow and become stiffer, so eventually reading vision is lost. This loss of reading vision with age is called presbyopia.

It is corrected with reading spectacles, and over time the strength of the reading spectacles must be increased. Myopia delays the onset of presbyopia, but brings with it its own problem of blurred distance vision.

There are a number of different approaches to treating presbyopia surgically. Perhaps the most successful technique for a lasting ‘cure’ is that of replacing the natural lens with a multifocal lens implant.

This can be made even more accurate if combined with the use of the state-of-the-art femto-second laser to carry out part of the surgery. Midland Eye is one of the few centres in the country able to offer this treatment option.