The macula is at the centre of the retina and is used for detailed activities such as reading and recognising faces, and is used to detect colours. Age-related macular degeneration usually involves both eyes, although they may not be affected at the same time. With the 'dry' form there is a gradual failure of the photosensitive cells of the retina. In general, magnification and high levels of illumination will assist in reading and other near vision tasks. A cataract is an opacity of the crystalline lens.
Cataracts can form at any age, but most often develop as people get older.
In younger people they can be present at birth or result from injury, certain drugs, radiation or conditions such as diabetes. The opacification of the lens may occur in different ways, so that the light rays which reach the retina may be split, causing multiple images. Age related cataracts are often yellow or brown causing loss of sensitivity to blue. The usual treatment is to remove the lens surgically and replace it with a plastic lens. Because there is no accommodation, spectacles are always needed for some purposes.