Macular degeneration leading to the impairment or loss of vision occurs under different conditions. The age related macular degeneration (AMD) is one of the most common cause of visual impairment in the elderly. In the US alone, it is estimated that at least 11 million individuals are afflicted by this condition. AMD occurs in nearly 30% of individuals who are older than 75 years of age. The advanced form of the disease occurs in about 7% of this population. Two types of macular degeneration are identified called dry and wet macular degeneration (table 1).

The wet type of macular degeneration may be treated with laser photocoagulation. However, there is no effective treatment for the dry type. The cause of the disease is unclear, however, environmental factors such as smoking, diet and the serum level of cholesterol are associated with increased risk of the disease. In addition, it is thought that genetic factors may also contribute to the development of the disease. Such genetic predisposition is now validated by the findings of Allikmets et al. These authors, in the September 19^th issue of Science, describe that the age related macular degeneration is associated with the mutation in the Stargardt Disease Gene (STGD1 or ABCR). This gene encodes a protein of the retinal rod photoreceptor which is mutated in the Stargardt Disease. This disease is the most common hereditary form of macular degeneration with an estimated incidence of 1:10,000. The ABCR protein is a member of the adenosine triphosphate-binding cassette (ABC) transporter superfamily and is involved in the transport of lipids, hydrophobic drugs and peptides. In 26 of the 167 patients that were studied, mutations in the ABCR gene was identified. The mutation consisted of both deletions as well as substitution of amino acids. Detection of these mutations would allow early identification of patients at risk for developing the disease.

REFERENCE: