AMD is the result of damage to the light-detecting nerve cells in the part of the eye called the macula. The process that leads to this damage is different for each type of macular degeneration.

• The dry form is a gradual process. As you age, the cells in the macula start to thin and break down, and waste deposits build up in the back of the eye. Over time, this damages the macula.
• The wet form happens when abnormal blood vessels grow in the back of the eye. These blood vessels break easily and leak blood and fluid under the macula. This can quickly damage the macula and distort your central vision.

Experts are still studying the causes of both forms. The cause of the damage to the nerve cells is unknown. A person's genes and family history may play a role.