Cataract is a cloudiness in the lens of the eye.

Normally, this tissue is completely clear and acts to adjust the focus of light rays entering the eye onto the retina to form a clear image.

The proteins which form the lens are normally very precisely layered and arranged and it is this feature which allows the proteins to be completely transparent. If this internal structure deteriorates and the proteins become damaged or disorganised, the lens itself starts to become cloudy or brownish and this interferes with the transmission of light back onto the retina.

There are several patterns of cataract formation but the end result is the same. The greater the cloudiness, the worse the vision becomes until finally only light and dark can be distinguished.

The early stages of cataract may have no symptoms at all but early symptoms include glare sensitivity, reduced perception of fine detail and reading difficulties. Work and domestic activities become affected, and activities such as driving become impossible.

Finally, the person becomes visually disabled if both eyes are affected, as they usually are. People who are blind generally have a severe reduction in their personal and economic quality of life and even die prematurely because of their blindness.

What causes cataract?

Cataract should be regarded as a 'risk factor' disease. The main risk factor by far is age. The incidence of cataract rises rapidly from the sixth decade (from the age of 50-60) and keeps rising until the end of life.

Other significant risk factors include family history, trauma, diabetes and a history of severe diarrhoeal infection.

This latter risk factor may help to explain the apparent higher age-specific incidence of cataract in countries like India.

Lesser risk factors include the use of some drugs, the presence of other eye conditions, particularly inflammation in the eye and sunlight exposure.

Children and babies can have cataract and sometimes be born blind from it. This is called congenital cataract and is uncommon. When it occurs however, it is very important because its early treatment can prevent a life of blindness.

Can cataract be prevented?

Because of the way the risk factors determine the likelihood of getting cataract, it can safely be said that it is not generally possible to prevent cataract.

Obviously however, the prevention of diabetes, the avoidance of eye trauma, the treatment of inflammatory diseases, the reduction of the burden of diarrhoeal diseases in communities and the avoidance of unnecessary use of certain drugs will result in some reduction of the load of cataract blindness.

There is some theoretical benefit in reducing direct exposure to sunlight, particularly in the early years of life.

General measures such as good nutrition, particularly having a diet rich in antioxidants, and avoidance of tobacco and excessive alcohol are sensible measures to take as well.

There is no known effective medical treatment which can prevent cataract from developing or slow its progress once it appears.

Access to screening and good quality specialist eye services is crucial for people with cataract to get appropriate and timely advice about management and the need for surgery. The prevention of cataract presents one of the great public health challenges.

Can cataract be treated?

The treatment of cataract is surgical. Basically, two things need to occur: firstly, the cloudy tissue has to be removed surgically and secondly, the lens power of the eye needs to be restored.

There are a number of ways to do these things and there have been different techniques used over the centuries.

Modern cataract surgery however has a number of specific features:

• It is one of the most successful and cost-effective surgical procedures of all time
• It is done by microsurgical techniques, using an operating microscope and specialised instruments
• It is done using local anaesthetic in most instances. Most people do not experience pain or distress from the surgery
• The cloudy tissue is removed from the internal part of the lens, leaving part of the lens capsule behind to act as a support for a lens implant called an intraocular lens (IOL).
• This IOL replaces the lens power of the eye and allows it to see more or less normally after the surgery. If an IOL is not used, the lens power has to be restored using either a thick spectacle lens or a contact lens. Both of these latter methods and the types of surgery used with them are fraught with problems and have largely been abandoned.

There is nothing mysterious about the process of removing the cloudy lens tissue. Because the central part of the lens is usually quite tough, to remove it requires an incision in the eye which is big enough to slide it out in one piece (Manual Extracapsular Cataract Surgery, or ECCE) or the use of a device to break it up inside the eye so that it can be flushed out through a very small incision. This device is called a phacoemulsifier (‘Phaco') and the surgery is called Phaco surgery.

A small incision is desirable because it is safer, the tecnique is faster and it heals rapidly without stitches (sutures), allowing a rapid return of good vision and normal activities.

If the incision is larger, then it usually needs to be sutured to seal the eye and hold tissues in a stable position while they heal. This adds time to the procedure and leads to a longer time to full recovery.

There is a technique of surgery, Small Incision Sutureless Cataract Surgery (SICS) which combines features of the small incision of Phaco surgery with the technological simplicity of ECCE. In most cases no sutures are used with this technique and the results are comparable to those of Phaco surgery.

Phaco surgery is now the standard of care for cataract surgery in developed countries but its high cost and the complexity of the equipment mean that ECCE and SICS are the main means used in low-resource countries. SICS is rapidly gaining in popularity because of its speed, low cost and rapid recovery time compared to ECCE.

People do not have to wait until they are blind to have cataract surgery. The time to have cataract surgery is when the benefit to the patient outweighs the small risk, cost and inconvenience to them and when the resources of the community can provide the service.

At the moment, in developing parts of the world, because of the lack of services, only people who are blind or severely disabled by cataract get the surgery and many people in desperate need never get it at all.

It is this situation which led to the formation of The Fred Hollows Foundation and is the main driver of its overseas work today.

The Foundation is working for a world in which no-one is needlessly blind from cataract or any other condition and, ultimately, for a world in which people can have access to cataract surgery when they need it, well before they go blind.

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Note: This information is general in nature and is not a substitute for specialist medical advice. Have your eyes checked regularly every two years, even if you have not noticed any symptoms or changes.