What is a cataract?

A cataract is a cloudiness or opacity of the lens inside your eye.

The lens begins life clear and flexible, so that it is able to change shape and focus for you to see up close. As we age, the protein structure in the lens changes and crystallises, so that the lens becomes cloudy (as an egg white when it is cooked). In the early stages, the hardening of the lens reduces the ability to focus up close, so that you start to need reading glasses. As the process progresses, you can start to experience glare in bright lights or while driving at night, with trouble reading in dim light. In the early stages glasses may be of help for reading, and then for distance. As the cataract becomes cloudier, you may reach the stage where you cannot see as well as you would like, even with glasses. This is when we start considering cataract surgery as an option.

As the cloudy lens or cataract is inside the eye, surgery involves making cuts in the eye, removing the cloudy lens, and replacing it with a clear plastic lens, so that the eye can see clearly. The lens power is calculated using equipment which measures the length of the eye and the surface curves of the eye. The lens power is usually selected so that the eye is in focus for distance. Sometimes weak glasses are needed to fine tune your distance vision. You will still need reading glasses to see up close.

The only possible way to see clearly without glasses at present is to remove one cataract and replace it with a lens that is in focus for the distance, then remove the other cataract and replace it with a lens which is in focus for near. This means that only one eye is in focus at any point in time and most people prefer to have their eyes working together. Multifocal lens implants are now available. They are more expensive and while many people are happy with them, they can cause problems with reduced vision, glare, haloes and trouble night driving (as can cataracts!).

Before considering cataract surgery

Before deciding whether to have cataract surgery, you will need to discuss with your doctor all the risks and benefits involved to find out what is the right decision for you. Benefits of the surgery involve clearer, brighter vision and the ability to drive without distance glasses. If you were very long-sighted or very short-sighted before the operation, this can be a very happy experience.

The risks of the surgery are small, and the surgery is successful in over 95% of cases. The risks do include haemorrhage and infection, potentially with loss of vision and even loss of the eye, so it is important to understand that surgery should only be considered if you are struggling with your vision, even with the use of glasses.