|MadSci Network: Medicine|
Hi Tony: Heterochromia iridis is a difference in the color of the iris in the two eyes. The amount of melanin in the iris stroma (deeper layer of this tissue) determines how light or dark an iris looks. The amount of malanin or loss of malanin can be attributed to several things. Heterochromia iridis can be due to a primary developmental defect (born with it) without functional loss. It can also be due to a disease state of the eye known as Horner's syndrome. Long standing Horner's syndrome can cause the affected iris to be lighter in color. Horner's syndrome idicates that there is disruption of the sympathetic nerve supply to the iris muscle, due to some other event elsewhere in the body. Some inflammatory conditions of the iris and/or associated structures can cause Heterochromia iridis, such as chronic uveitis and iritis. This is not a medical diagnosis, and if you want further information, I would suggest a book referenced below. I hope this helps! Kenton L. McWilliams, O.D. General Ophthalmology - 14 th edition Daniel Vaughn, M.D. Taylor Ashbury, M.D. Appleton and Lange 1995
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