Cataracts

Nerve messages pass from the 'seeing cells' (rods and cones) in the retina down nerve fibres in the optic nerve to the brain. The messages are interpreted by the brain which enables us to see.

 

For us to see clearly and sharply, the lens of the eye has to be clear (transparent) - just like the lens in a camera.

 

 

Cataracts are cloudy (opaque) areas that develop in the lens of an eye. The lens should normally be clear but if you develop cataracts the affected lens becomes like 'frosted glass'. Depending on the severity of the cataract, the effect on your sight can range from vision being slightly blurred to complete blindness in the affected eye.

 

Some people have the wrong idea about cataracts. For example, some people wrongly think that a cataract is like a 'skin' that forms over the eye or lens. This is not true. A cataract is a gradual change in the structure of the lens in an eye which makes it gradually more and more 'cloudy'.

 

 

There are different types of cataracts.

 

 

This is by far the most common type and affects older people. It becomes more common with increasing age. In the UK about 1 in 3 people over the age of 65 have a cataract. Men and women are equally affected. Often both eyes are affected, but one eye may be worse than the other.

 

Typically, an age-related cataract forms gradually over many years. Many people with an early cataract do not realise they have it as the cloudiness caused by an early cataract is not too bad and the vision is only mildly affected. In some people, the cataract does not become too severe. However, in many cases vision becomes gradually worse over the years.

 

 

These are uncommon but important to diagnose early. This is because vision and seeing has to be learnt very early in infancy. A cataract that is present at birth stops the eye from learning to see and can cause blindness which may persist even if the cataract is removed later in life. A congenital cataract must be removed as early as possible after birth. This is why a doctor will examine the eyes of babies as part of routine baby checks.

 

 

There are some uncommon causes of cataract. A cataract may develop after an injury to an eye, or as a result of radiation exposure. Cataracts sometimes develop as a 'secondary' problem if you have another condition. For example, as a complication of some other eye conditions, and some people with diabetes develop cataracts.

 

 

 

The cause is not entirely clear. There seems to be a change to the structure of the proteins in the lens. This may be caused by a disturbance in the way fluids and nutrients get to the lens as you become older. Some of the proteins may then clump together in places within the lens. This causes tiny areas of cloudiness. Each tiny area of cloudiness blocks a bit of light getting past to the retina. The severity of the cataract depends on the number of areas of cloudiness that develop in the affected lens.

 

Most affected people develop cataracts for no apparent reason. Factors that may increase the chance of developing cataracts include: a poor diet, smoking, a lot of exposure to ultraviolet light, diabetes, steroid medicines, a family history of cataracts (a 'genetic predisposition').

 

 

At first you may notice your vision becoming a bit blurred. You may notice 'spots' in your vision. Some people with cataracts notice halos around bright lights, for example, street lights. You may not be able to see as well in brightly lit rooms or in sunshine. You may easily become dazzled by bright lights such as the headlights of an oncoming car. Over the years your vision may gradually becomes worse and cannot be corrected by glasses.

 

 

A cataract can usually be seen easily by a doctor or optometrist (optician) when they examine your eyes. This may be done because you have noticed a problem with vision. Sometimes an early cataract is detected before you have noticed a problem with vision during a routine eye check.

 

 

An early cataract may not cause any noticeable problem with your vision. The rate of decline in vision varies considerably from person to person. If you have an early cataract and your vision is good then treatment is not necessary. But let a doctor know if your vision does get worse and affects your life.

 

Treatment is an option when a cataract becomes bad enough to interfere with your normal life. For example, if vision becomes bad enough to interfere with reading, driving, watching TV, cooking, looking after yourself or others, or stops you doing anything you would normally do. Treatment is normally successful. However, you have to balance the small risk of complications from treatment against how much the cataract is affecting your life and your desire for treatment. Before making a decision about treatment, make sure your glasses are giving you maximum benefit. In later life it is a good idea to have regular eye checks to make sure that your glasses prescription is still the correct one for your eyes.

 

 

Treatment is to remove the cloudy lens and replace it with an artificial plastic lens (an intraocular implant). The common operation in the UK is called Phaco Extracapsular Extraction, sometimes called Phacoemulsification. (This is just a medical way of describing the way the lens is removed.) It is a routine operation that usually takes 10-30 minutes. It is often done as a 'day case'.

 

 

In most cases the operation is done under local anaesthetic. This means that you are awake during the operation but it is not painful because local anaesthetic eye drops are used to numb your eye. (Sometimes local anaesthetic injections are used around the eye.)

 

When the eye is numb, the surgeon makes a tiny hole in the front of the eye at the edge of the cornea. Then, the surgeon pushes a tiny thin instrument into the lens through the front part of the lens capsule. The instrument emits ultrasound waves that breaks up the contents of the lens within the lens capsule.

 

The contents of the lens are then removed by suction through a needle. Once the lens material is removed, a clear plastic lens is placed within the lens capsule through the hole made in the front part of the lens capsule. The back or 'posterior' part of the lens capsule remains intact for the plastic lens to be kept in place. (In some cases, a plastic lens cannot be used. In these cases special contact lenses or glasses are worn to replace the function of the lens.)

 

 

The operation described above is the most common operation in the UK as it involves just a tiny cut and has a low rate of complications. Another technique that is sometimes done is called manual extracapsular extraction. For this the surgeon makes a slightly longer cut on the side of the cornea and removes the center of the lens without first breaking it up with ultrasound waves (as is done in Phaco Extracapsular Extraction.) Again, the posterior capsule is left in place and a plastic lens is put in to replace the removed lens.

 

Another operation option is called Intracapsular Extraction. In this, the whole lens is removed, including the capsule. After it is removed, either a plastic lens is sewn into the eye, or special glasses are worn to replace the function of the lens. Intracapsular Extraction is not done very often in the UK these days as the above operations are thought to be better with less risk of complications. However, it is still often done in developing countries where the equipment needed for the more modern operations is not available.

 

 

In the vast majority of cases, the operation is successful and vision improves immediately. In a small number of cases, complications occur such as bleeding into the eye, infection, inflammation of the eye, and damage to the cornea or other parts of the eye. These are all uncommon, can often be treated, but are sometimes serious enough to cause permanent visual problems.

 

 

This is a complication that sometimes occurs following Phaco Extracapsular Extraction or Manual Extracapsular Extraction. In these procedures, the back (posterior) part of the lens capsule remains after the operation. Sometimes this thickens several months after surgery, becomes cloudy (opacifies), and affects vision. If this occurs it can usually be easily treated with a painless procedure using a laser. The laser can 'burn' a hole in the middle part of the capsule which then allows light through and restores vision. (Note, a laser cannot be used to treat a cataract itself, only this possible complication that sometimes occurs following cataract surgery.)

 

©EMIS and PIP 2005   Updated: May 2006