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Cataracts

This factsheet is for adults who have cataracts.

A cataract is a painless clouding of the lens of the eye. Cataracts generally develop over a long period of time, gradually worsening the eyesight. They can eventually lead to blindness.

Cataracts are common in older people. About a third of people over 65 have cataracts in one or both eyes. They can usually be treated with surgery, but not all people need to have them removed, provided that they don't significantly reduce vision.

The eye

Your eye is a spherical structure that contains fluid.

Near the front of your eye is the lens, which sits behind the iris - the coloured part of your eye. The lens helps you to see things in focus. It focuses light rays onto the back of the eyeball (retina), to form an image, which is then transmitted to your brain.

Illustration showing the structure of the eye

The lens is normally a clear structure, made mainly from water, which can change its shape to allow you to focus on near and distant objects.

What are cataracts?

A cataract is a clouding of the lens in the eye that may reduce your vision. The lens becomes more opaque and is therefore less able to transmit light rays onto the retina. The image on the back of the eye is then blurred.

The structure of the lens also changes as the lens becomes less transparent.

Often both eyes are affected.

Different types of cataract

There are different types of cataract, some of which are due to rare diseases or as a result of local eye injuries or inflammation (see What causes cataracts? below). However, the two main types are:

• senile (age-related) cataracts - the most common type
• congenital (present at birth) cataracts which are relatively rare but important to diagnose early since vision and 'seeing' have to be learnt very early in infancy (cataracts present at birth stop the eye from learning to see and can cause blindness even if removed later in life)

This factsheet is about adult cataracts.

Symptoms

You may get one or more of the following symptoms:

• a worsening of your vision which may make you feel like your vision is cloudy, fuzzy or filmy
• spots in your vision
• glare and halos from lights or the sun - this may be severe, and you may also have difficulty driving at night
• double vision
• difficulty in telling the difference between colours, especially shades of blue
• frequent changes in glasses prescription as eyesight deteriorates
• second sight - your close-up vision and reading may improve temporarily as the lens changes shape

What causes cataracts?

In the UK, most cataracts develop as people get older, and usually they are first noticed around the age of 50-60. The reason why is not yet known. One theory is that it is caused by a disturbance in the fluids and nutrients in the lens.

In younger people there are certain factors that can increase your risk of getting cataracts. These include:

• diabetes - this can cause a secondary cataract to develop
• an injury to the eye
• exposure to ultraviolet light from sunlight
• medication use such as long-term use of steroid tablets
• smoking
• heavy drinking
• a family history of cataracts

Diagnosis

A GP, an optician or an ophthalmologist (eye specialist) can diagnose cataracts by looking into your eyes with a special viewing instrument called an ophthalmoscope.

Testing your vision by using standard charts may show deterioration in your eyesight. It's quite common to be diagnosed with a cataract during a routine eye test.

Treatment

For some people, their loss in vision is mild enough to get along fine with glasses or contact lenses and to delay surgery. The time to consider treatment is if your vision has become noticeably worse and this is interfering with your everyday activities such as work and hobbies.

So far, no medication or diet has been found to slow down the growth of cataracts, and there is no medication that can clear a clouded lens.

Wearing glasses may improve vision for those in the early stages of cataract development, but your cataract will probably get worse over time so this will provide only a temporary solution.

Left untreated, the lens will eventually become so clouded that it is impossible to see any detail at all, although some light will always be distinguishable.

Surgical removal of your cataract is the only way to restore or maintain your vision. This involves replacing your damaged lens with an artificial one. The most common technique is called phacoemulsification. For more information, please see the separate BUPA factsheet:
Cataract surgery

Prevention

You can wear sunglasses that block out UVA and UVB rays to help reduce your chances of getting cataracts as a result of damage from ultraviolet light in sunlight.

There is no way to prevent cataracts that develop as a result of getting older.

Further information

• Royal National Institute of the Blind
  0845 766 9999
  www.rnib.org.uk
• Royal College of Ophthalmologists
  www.rcophth.ac.uk

References

• Cataracts. UK Department of Health. PRODIGY patient information leaflet.
  www.prodigy.nhs.uk
  accessed 15 July 2005
• Cataract surgery guidelines 2004. The Royal College of Ophthalmologists.
  www.rcophth.ac.uk
• Understanding cataracts. Royal College of Ophthalmologists.
  www.rcophth.ac.uk
  accessed 15 July 2005
• Simon C, Everitt H, Birtwistle J, Stevenson B. Oxford Handbook of General Practice. Oxford: Oxford University Press, 2002:800.
• Effects of ultraviolet radiation on human health: report of an advisory group on non-ionising radiation. Health Protection Agency. Documents of the NRPB: Volume 6, No 2.
  www.hpa.org.uk

Published by BUPA's health information team, healthinfo@bupa.com, September 2005

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