Age-related macular degeneration (AMD) is a deterioration or breakdown of the eye's macula. The macula is a small area in the retina — the light-sensitive tissue lining the back of the eye. The macula is the part of the retina that is responsible for central vision, allowing you to see fine details clearly.
There are two types of macula degeneration:
There is a break down of tissue and build up of deposits called drusen in the macula region. This happens slowly and there is a gradual deterioration with vision becoming blurry. Distortion can be present but is usually mild.
This is usually more sudden and often results in the affected eye seeing straight lines and objects as markedly distorted. It occurs due to a leakage of fluid from abnormal blood vessels in the macula region.
Excellent information on macular degeneration is available from the American Academy of Opthalmology website here