Age-related macular degeneration
Age-related macular degeneration is a common eye disease that causes central vision loss in older adults by damaging the macula, the part of the eye responsible for detailed vision.
Overview
Age-related macular degeneration (AMD) is a leading cause of vision loss in older people. While subtle abnormalities may appear in a person's forties or fifties, distorted vision and vision loss typically become noticeable in the sixties or seventies and worsen over time.
Types of AMD
- Dry form: Accounts for 85 to 90 percent of cases. It is characterized by the buildup of yellowish deposits called drusen beneath the retina. The most advanced stage is geographic atrophy, where areas of the macula waste away.
- Wet form: Occurs in 10 to 15 percent of cases. It involves the growth of abnormal, fragile blood vessels underneath the macula that leak blood and fluid, causing rapid and severe vision loss.
Causes and Risk Factors
AMD results from a combination of genetic and environmental factors:
- Genetic factors: Many genes involved in the complement system (part of the immune response), such as the CFH gene, contribute to risk. Variations in the 10q26 region of chromosome 10, including the ARMS2 and HTRA1 genes, are also associated with increased risk.
- Environmental factors: Age is the most significant risk factor. Other factors include smoking, high blood pressure, heart disease, obesity, exposure to ultraviolet (UV) rays, and diets high in fat or low in antioxidants and zinc.
Inheritance
AMD does not have a clear-cut pattern of inheritance, though it often runs in families. Approximately 15 to 20 percent of affected individuals have at least one first-degree relative with the condition.