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Age-related macular degeneration

Age-related macular degeneration is a common condition that causes gradual loss of vision among individuals over the age of 50. It is caused by a combination of genetic and environmental risk factors.

Characteristics of Age-related macular degeneration
Age-related macular degeneration (ARMD) slowly destroys the macula, the center part of the back of the eye that makes vision sharper and more detailed. The vision loss that occurs affects the central vision, which is most critical for activities like reading and driving. In some individuals, ARMD can develop so slowly that they may not realize they have it, while in others, the condition progresses quickly, resulting in a rapid loss of central vision in one or both eyes. There are two types of ARMD: dry and wet. Dry ARMD is more common than wet ARMD, and wet ARMD is thought to be a more advanced and severe type of ARMD.
Some signs and symptoms of ARMD are blurry vision, the need for increasingly bright light to see up close, difficulty seeing when going from bright light to dim light, trouble or inability to recognize peoples faces, colors appear less vivid or bright, and blank, hazy or dark spots.

Diagnosis/Testing
ARMD can only be detected by a comprehensive dilated eye exam. Although there are many factors that influence an individuals risk of developing ARMD, changes or variants in certain genes, such as variants in the CFH gene and many others, appear to be responsible for approximately 50% of the reasons for individuals developing ARMD. In addition to genetic factors, age is also a risk factor of ARMD; as individuals get older, the risk of developing ARMD increases. It is thought that individuals in their 50s have a about a 2% chance of developing ARMD, and this risk increases to nearly 30% in those over the age of 75. Other risk factors include smoking, high blood pressure, high cholesterol, and obesity. Women appear to be at greater risk of developing ARMD than men. Additionally, compared to African Americans, European Americans are more likely to develop ARMD.

Management/Surveillance
Treatment for individuals with advanced ARMD includes use of medications, photodynamic therapy (i.e., a treatment that combines a medication with a specific type of light to destroy new eye blood vessels in order to slow the rate of vision loss), and laser surgery. Once vision loss occurs, however, it cannot be reversed. For individuals with ARMD and vision loss, the use of low vision aids (e.g., large-print reading materials, talking watches and clocks, and magnifiers) can be helpful.
Although genetic factors account for approximately 50% of the reason for ARMD developing in an individual, non-genetic factors play a large role as well. Regardless of the presence or absence of genetic factors, it is important for all individuals to have regular comprehensive dilated eye exams.
Research suggests that a healthy diet, especially one rich in green, leafy vegetables and fish, and avoiding smoking may lower the risk of developing ARMD. Additionally, taking prescribed vitamins and minerals may reduce the risk of developing advanced ARMD.

Mode of inheritance
ARMD is a complex condition, which means that it is caused by a combination of many different factors. These factors can be genetic or non-genetic (such as environmental factors and lifestyle choices such as smoking). Complex conditions are inherited in a multifactorial pattern. This means that the chance for an individual to develop ARMD is influenced by the number and type of genetic and non-genetic factors occur together to which an individual is exposed. In other words, no single gene, and no single environmental factor cause ARMD. However, not all of these genetic factors and environmental factors are known.

Risk to family members
It is estimated that approximately 15-20% of individuals with ARMD have a close relative (e.g., parent, sibling or child) who also has ARMD.

Special considerations
None

Resources
National Eye Institute
eyeSmart
AMD Alliance International
BrightFocus Foundation
Genetics Home Reference: Age-related macular degeneration

References
Bergeron-Swaitzke, J. et al. (2009)."Multilocus analysis of age-related macular degeneration." European Journal of Human Genetics 17:1190-1199.
Seddon JM, et al. (2005)."The US twin study of age-related macular degeneration: relative roles of genetic and environmental influences." Archives of Ophthalmology 123(3): 321-327.
Swaroop, A. et al. (2009)."Unraveling a Multifactorial Late-Onset Disease: From Genetic Susceptibility to Disease Mechanisms for Age-Related Macular Degeneration." Annual Review of Genomics Human Genetics. 10:19-43.

Created:01/2013

Updated:mm/yyyy

Created by:Seema Jamal, MSc, LCGC

Edited by:Michael Bamshad, MD



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