Retinitis pigmentosa (RP) is a group of genetic diseases that causes slow, progressive loss of vision. This loss of vision results from the gradual degeneration of cells in the retina, the light-sensitive tissue that lines the back of the eye.
How common is RP?
RP is considered to be a rare disorder. General estimates suggest that this condition affects approximately 1 in 4000 people.
What causes RP?
RP is typically an inherited disorder due to mutations that may be present in any one of over 50 genes. These genes provide instructions for making essential proteins for retinal cells, or photoreceptors. Some of these mutations produce proteins that are toxic to the photoreceptors, some produce proteins that do not function properly, and other mutations are so extensive that the gene cannot make any protein at all. All of these changes damage the photoreceptors and thus limit their function.
What are the Symptoms of RP?
The main symptoms of RP are night blindness (or difficulty adjusting to the dark) and loss of side vision. Loss of peripheral vision makes mobility, and daily activities such as driving, reading and recognizing faces and objects very difficult. At this point, central vision is most of what remains.
The symptoms RP are often first noticed in childhood or young adulthood. An individual affected by RP may have difficulty moving around in the dark, and may take an abnormally long time to adjust to changes in lighting conditions.
As the loss of peripheral vision becomes noticeable, patients often bump into things and appear clumsy. Additionally, people with RP often experience discomfort in bright lights.
Because there are so many different mutations that can result in RP, its progression can vary dramatically between those affected. Unfortunately, most people with RP eventually lose most of their sight.
How is RP diagnosed?
RP can be diagnosed in part by a thorough retinal examination. An eye care professional will want to dilate your pupils to allow for a clearer view of the retina. In RP, dark pigmented deposits in the peripheral retina are often noted. Other tests to aid in the diagnosis include:
- An electroretinogram or ERG – a test that measures the electrical activity of the photoreceptors. RP causes a decrease in the electrical activity of the photoreceptors as their function decreases.
- Visual field testing – a visual field is a way of mapping the extent of an individual’s vision. It is most often used to measure the amount of vision loss.
- Genetic testing – such testing helps an individual to understand the progression of their particular strain of the disease.
How can RP be Treated?
Unfortunately, there is no cure or treatment for RP. Developments, most notably in the area of genetic research, are currently being made.