Sorsby fundus dystrophy causes similar symptoms to age-related macular degeneration (AMD), although it generally affects people at a younger age.
How is it inherited?
Sorsby fundus dystrophy is inherited in an autosomal dominant fashion. That means that someone who inherits the faulty gene from either of their parents will develop the condition. There is a 50 per cent chance of an affected parent passing the condition on to each of their children. It affects equal numbers of men and women.
What are the symptoms?
One early symptom is night-blindness. Some research suggests that difficulty distinguishing blue from green, and yellow from red can be an early sign of Sorsby fundus dystrophy too. Later (usually when people are in their 40s) macular cells start to die off, and new blood vessels may grow into the retina, causing loss of central vision.
There is currently no proven treatment for Sorsby fundus dystrophy. Anti-VEGF injections such as Avastin® or Lucentis® have both been shown to be effective in controlling the growth of new blood vessels in Sorsby fundus dystrophy.
It’s important for Sorsby fundus dystrophy to be diagnosed early and confirmed by genetic testing. That means we can give people a better idea of how their sight loss is likely to develop, and look out for the symptoms of new blood vessels growing in the retina.
Symptoms are caused by one of several mutations in a gene called TIMP3, on chromosome 22q. We think the mutation causes cells to make a harmful version of the TIMP3 protein.
Studies have found that treatment with high doses of vitamin A can reverse night-blindness in people with Sorsby fundus dystrophy. This suggests that the first symptoms are caused by Bruch’s membrane becoming thicker and less permeable. The thickened membrane stops vitamin A and other nutrients getting to the light-sensing cells, which gradually stop working and eventually die.