The eye is similar to a camera. Light is focussed by a lens on to a light sensor. If the camera lens is dirty, the picture will be blurred. A cataract is a clouding of the lens inside the eye. There are a number of types of cataracts - each of which causes different changes to vision. Posterior subscapsular cataracts occur centrally and cause a significant reduction in vision. Cortical cataracts occur in the periphery of the crystalline lens. Vision is therefore affected later as the cataract progresses. Nuclear cataracts cause the lens to become a yellow, murky brown colour. Vision is usually blurred and colours less vibrant. Factors such as U.V. light exposure, smoking, prolonged use of steroids and diabetes increase the risk of cataracts. Protect your eyes with quality sunglasses. Certain eye supplements or a balanced diet of fruits and leafy green vegetables can delay the onset of cataracts.