What is retinitis pigmentosa (RP)?
Retinitis pigmentosa is a group of many genetic retinal disorders that are generally lumped together under the one term of RP. It can appear in a person with no other affected family members, as a dominant trait (an affected individual has a 50% chance for each child getting the disease), as a recessive trait (each parent carries the gene but does not show any signs of RP themselves), or as sex-linked trait (passed from a usually unaffected mother to half of her sons who are usually affected and to half of her daughters who are usually unaffected carriers).
RP primarily affects the rods and cones, the retinal cells responsible for capturing the light images in our eyes. The genetic defect in these cells causes the outer retinal layers to atrophy, with the pigmented layer of cells below the retina (the retinal pigment epithelium, or RPE) typically migrating into the retina in a bone-spicule pattern. There is an increased risk for cataracts and cystoid macular edema. Most patients have variable symptoms of night blindness, difficulty adjusting to a dark environment, side vision loss, and central vision loss.
How is a RP diagnosed?
RP is usually diagnosed during a dilated ocular examination. Most affected patients will have a typical appearance of bone spicules, a pale optic nerve, and narrowed retinal vessels, OCT scanning, fluorescein angiography, and electroretinogram (ERG) are often used to confirm the diagnosis. Visual field testing typically shows mild to severe side vision loss that can result in ‘tunnel vision.’
How is RP treated?
There are no specific treatments for the underlying genetic changes. Although a great deal of research is underway, we still don’t know in most cases what actually causes the rods and cones to malfunction and degenerate. However, patients still need to be examined regularly since both cataracts and macular edema are often treatable. Vitamin A palmitate (15,000 international units) has been shown to possibly slow the disease progression, and may be recommended for some.
Many patients are able to maintain a normal active life, although some will develop legal blindness due to peripheral or central vision loss. Low vision services or referral to the Department for the Blind can help severely affected individuals maintain their independence. Exciting new technologies, such as the Argus 2 device, offer much potential promise in restoring lost vision in those severely blind from this disease.