What is a cataract?

A cataract is a clouding which develops in the lens of the eye. This cloudiness obstructs the passage of light through the eye to the retina and results in a blurry, unfocussed image.

A medical illustration showing a cross-section of an eye with a cataract. The natural lens is shown as cloudy and grey. Because the lens is not clear, the letter ‘A’ becomes a blurry, unfocussed image on the back of the eye.

Symptoms

Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both eyes, although it can, and often does, affect one eye more than the other.

Cataracts are usually age-related and are more common over the age of 65. Most people will have developed some degree of cataract by the age of 90. Other causes of cataract include diabetes, steroid (or cortisone) use, previous ocular surgery, trauma and in some cases may be hereditary.