Understanding Cataract Surgery

What is a cataract?
What causes cataract?
How does cataract affect your sight?
When should you have cataract surgery?


What is a cataract?

Cataract is a clouding or opacity of the eye’s natural lens.

It is helpful to know a little about the eye and how it works in order to understand the effect cataract has on your vision, and how it can be treated.

Anatomy of a normal eye

The cornea forms the clear window into the eye. The iris, which is the coloured part of the eye with the black pupil in the middle, is behind the cornea. The lens lies behind the iris. In a healthy eye the lens is clear and able to focus light on to the retina, the light-sensitive nerve layer that lines the inside of the eye.

The wall of the eye is formed of three layers, the retina, the choroid and sclera. The choroid is the underlying vascular (blood vessel) layer of the eye from which the retina receives oxygen and nutrients. The sclera or “white of the eye” forms a tough protective coat.

The retina sends signals via the optic nerve to the brain, where sight is interpreted. This process can be likened to the lens in a camera focusing light on to photographic film, from which images can be developed.

In a normally-sighted eye, a healthy young lens has the ability to adjust the eye’s focus, letting us see things clearly both near and far away. Many people begin to lose this ability when they reach middle age, finding for the first time that they need a spectacle correction for reading; this is called presbyopia.

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What causes cataract?

Cataracts are generally associated with the normal ageing process. Surprisingly this may cause a temporary improvement in your near vision, but this effect is short-lived and disappears as the cataract worsens.

Cataract may develop prematurely in certain situations, for example;

  • following direct injury to the eye;

  • in medical conditions such as diabetes;

  • in patients taking steroid therapy;

  • following previous eye surgery or inflammation;

  • presenting at birth - congenital cataract.

Many people consider poor vision to be inevitable as they get older, but for the vast majority of patients with lens opacity, cataract surgery is an extremely successful procedure to restore vision.

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How does cataract affect your sight?

Symptoms of cataract:

  • blurred vision especially for distance;

  • glare from bright lights, especially headlights at night;

  • spectacles seeming dirty or scratched;

  • frequently changing spectacle prescription;

  • colours appearing washed out or faded;

  • double vision in the affected eye.

There are different types of cataract and the visual effect you experience may depend on the type you have. Cataracts do not cause pain or redness. If you have either of these symptoms you should report this.

Cataract begins slowly and at first may have little effect on your vision. Your local optometrist may be able to improve your vision with a change in spectacle prescription during the early stages. As the lens becomes cloudier however, it interferes with light rays passing to the retina, with sight becoming increasingly blurred. You will reach a stage at which a change in spectacle prescription no longer improves your vision.

Comparison of a healthy eye with a clear lens and an eye with lens opacity

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When should you have cataract surgery?

There is no specific level of vision at which surgery is indicated, but as soon as your impaired vision interferes with your daily life the procedure is worth considering. You may notice your impaired vision when reading, working, watching TV, driving, playing sport or caring for others.

If you are a driver you must be able to achieve the visual standard required by the DVLA and it may be necessary to have cataract surgery to keep your licence.

Leaving a cataract untreated does not damage the eye, but as the lens opacity worsens your vision will deteriorate until little sight remains. Surgery at this stage may be more difficult.

Complications can arise if the thickened lens causes eye pressure to increase, but this is unusual and we will inform you if you are at risk of this happening.

In the past, eye specialists delayed surgery until a cataract was “ripe” or “mature”. Surgery involved a large incision in the eye which required sutures (stitches) at the end of the procedure, and the outcome of surgery was less predictable.

Cataract surgery is now performed earlier due to major developments in the surgical technique itself, the very low risk of complications and visual benefit of modern intra-ocular lenses (IOLs).

Surgery involves removing your cloudy lens and replacing it with a clear, plastic implant lens which you cannot feel and which remains permanently in your eye.

If you require cataract surgery to both eyes, we will decide with you which eye should be dealt with first. Surgery will be carried out on only one eye at a time, usually with an interval of one or two weeks between the two procedures.

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