Retinitis pigmentosa (RP) consists of a large group of disorders resulting from a progressive loss of the rods and cones in the retina. These are the cells that respond to light and send signals to the brain that enable us to see. More than 100 mutant genes have been identified as responsible for these hereditary disorders and there is considerable variation in onset and progression of symptoms. The disease usually is present as an isolated eye disease but syndromal forms also occur in which there is a similar disease of the retina in association with other disease elsewhere in the body.
The first symptoms consist of difficulty seeing at night followed by constriction of side vision and these typically appear in young adults. Later, sensitivity to light appears together with color vision difficulties. About this time fine vision is lost as well and some patients are legally blind by the 6thdecade. Eye examinations usually show clumps of black pigment in the retina and the optic nerve that connects the retina to the brain shows damage as well. Cataracts occur in up to 50% of adult patients.
A considerable number of individuals with retinitis pigmentosa have n family history of this disease but in others there is a pattern of inheritance called autosomal recessive. In this case both males and females can have RP when they inherit two mutated copies of certain genes. More than 30 genes have been implicated and each one may have multiple different mutations. Both parents must carry one copy of the gene change (though they do not have the disease), and transmit it to their children before the disease manifests itself. Such parents can expect on average that 25% of their offspring will have this form of RP.
The disease is usually diagnosed by an ophthalmologist based on the symptoms and the appearance of the retina. An electrical test called an ERG is often used to confirm the diagnosis. There are no signs of disease outside of the eye in most cases. Lifespan is not impacted.
Low vision aids and mobility training can be great benefit. High doses of vitamin A palmitate have been shown to slow the progress of the disease but this requires careful monitoring to avoid complications of liver damage. Several new therapies are under investigation but these are not yet clinically useful.
Cataract surgery is indicated in patients when the lens opacities interfere with vision.