CataractsA cataract is a painless clouding of the internal lens of the eye. Light enters the eye through the transparent lens, and is focused onto the retina at the back of the eye. The retina transmits the visual signal through the optic nerve to the brain where the image in interpreted. Because they block light from passing through the lens, cataracts make it difficult to see clearly and can even cause blindness over time.

Cataracts are progressive, and are the leading cause of vision loss in people over the age of 40, although sometimes they can be seen in younger people. Congenital cataracts can be present at birth or appear shortly after or at some time during infancy or childhood.

How do cataracts affect vision?

While cataracts are painless and not hazardous to the health of the person or the eye, over time they can interfere with day to day functioning. They develop gradually, often in both eyes but seldom equally. Because they develop slowly, most people are unaware of the vision loss at first, but as the clouding progresses, the person finds difficulty with distance vision, reading in low light or driving, particularly at night.

Symptoms of cataracts

The main symptom of cataracts is blurry or cloudy vision at any distance. Other problems with the eyes can also cause blurry vision, but cataracts produce certain characteristic symptoms, which may include worse vision in dim light, sensitivity to bright light or glare, even indoors, a perception that colours are faded or not clear, double vision when looking through only one eye, and small spots in the field of vision. The phenomenon known as "second sight" may occur, in which the cataract acts as a stronger lens, temporarily improving close vision, but as the cataract worsens, this temporary improvement disappears. Cataracts do not change the appearance of the eye.

Glasses may need to be changed frequently, but eventually reading becomes more difficult and wearing glasses is less effective. As vision deteriorates, and the glare of oncoming headlights and street lights gets worse, driving becomes stressful, and even dangerous. Drivers with cataracts start to experience eyestrain and find themselves blinking more frequently as they try to clear their vision.

If the cataract becomes hypermature, or completely white, there may be inflammation, headache, and some pain. A hypermature cataract that causes pain or inflammation needs to be removed.

Who is at risk?

Because the greatest risk factor is age, anyone can develop a cataract. However, certain factors increase the risk. These include family history, diabetes, previous eye injury or inflammation, smoking, long-term exposure to harmful UV rays from sunlight, and extended use of corticosteroids.

Diagnosis of cataracts

An optometrist can detect a cataract by conducting a thorough eye examination. Tests performed may include a visual acuity test to assess how clearly a person can see; a slit-lamp examination to inspect the cornea, the iris, the lens, and the space between the iris and the cornea; tonometry to measure the pressure inside the eye; and an examination of the retina using eye drops to dilate the pupils, which gives the optometrist a larger view of the back of the eye.

Treatment of cataracts

During the early stages of cataract development, stronger glasses may help improve vision. Other solutions include using a magnifying glass for reading, wearing sunglasses to reduce glare, brighter lighting in the home, and avoiding night driving when possible. However, these are temporary measures, because the cataracts will continue to develop and the eyesight will deteriorate.

Surgery to remove cataracts may be required if the related vision loss cannot be corrected with glasses or contact lenses. There are various types of cataract surgery, all of which involve removing the cloudy natural lens and replacing it with an artificial lens. Different types of replacement lens may be used: a monofocal lens is a fixed-strength lens that is set for one level of vision, usually distance; a multifocal lens may have two or more different strengths, providing for near and distance vision; an accommodating lens is most similar to the natural human lens as it allows the eye to focus on near and distant objects. A discussion with your optometrist or ophthalmologist will help in the choice of the most appropriate lens for your needs.

The operation is usually done on an outpatient basis and is generally safe and effective. For those who need surgery on both eyes, the surgery is usually done on one eye at a time.

After surgery, your eyes may itch and feel sensitive to light for a few days. You may need to wear a shield or glasses for protection, and you may be prescribed eye drops to speed the healing process. For most patients, vision improves almost immediately, although it may take a few weeks for the eye to settle down and vision to stabilise. Glasses may still be necessary for distance vision or reading, after the surgery.

Vigorous activities should be avoided for a while, but most people find they can go about their daily activities straight after the surgery.

Can Cataracts be prevented?

It has been suggested that certain steps can be taken to reduce the risk of developing cataracts. Smoking raises the risk for a number of eye conditions, and there are indications that cataract symptoms appear earlier in smokers than non-smokers. A healthy diet reduces the risk of disease, including eye problems. As part of good nutrition, lutein and zeaxanthin, which are found in green leafy plants and colourful fruits and vegetables, have been described as "promising" in preventing cataracts. Maintaining a healthy weight and keeping diabetes under control will help reduce the risk. Wear sunglasses that block UV radiation when in sunlight.