What Is A Cataract?

The eye is rather like a camera. Like a camera there is a lens inside the eye. This lens sits just behind the pupil and should be transparent. If for any reason the lens of the eye becomes cloudy or hazy the patient is then said to have a cataract, see figure 1.1.

Figure 1.1 - Cortical Cataract (below)

Doctors and opticians tend to use the word "cataract" in a strict medical sense meaning any haziness of the lens even if the patient has normal vision. A better and patient orientated definition of cataract is therefore: "a clouding of the lens within the eye that is reducing vision."

There are different types of cataract and various reasons why cataracts develop. However the main cause of cataract in the developed world is age. In young children the lens of the eye is crystal clear. As we age the lens gradually becomes less clear and yellowed. In the elderly the lens of the eye has a brown hue.

Figure 1:2 - Schematic Picture of Eye (below)

A cataract is not a skin on the eye. This is a false belief that is only slowly being removed from public thinking. There are some other conditions that look like a skin growing over the eye but this is not cataract.

Cataract is another word for waterfall. The name arose because in ancient civilisations the loss of vision was thought to be due to a bad humour falling down from the brain to obscure vision. In a mature cataract the pupil may become white and this does look rather like the white water within a waterfall.

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