Retinitis pigmentosa is a term used to describe a group of eye diseases that damage the retina. The retina is the layer of tissue located in the back of the inner eye that converts light images to nerve signals and transmits them to the brain. Also known as RP, retinitis pigmentosa is a slow and progressive disease that causes the photoreceptor cells (the rods and cones) to die, which leads to a loss of vision.
Although complete blindness is uncommon, it can occur. Some people are deemed legally blind by their forties or fifties, while others retain some of their vision throughout their lives. There are different forms of RP, including rod-cone disease, Usher syndrome, Leber’s congenital amaurosis, and Bardet-Biedl syndrome. It is estimated that one in every 3,700 Americans suffers from retinitis pigmentosa. Worldwide, it’s reported in one person in every 5,000. Ethnically, Navajo Indians show the highest predisposition, with one in every 1,878 developing RP. Many experts believe it is caused by genetics; although, in 45–50 percent of cases only one family member is affected.
Symptoms of Retinitis Pigmentosa
Symptoms may or may not depend on whether rods or cones are involved initially. In most cases, the rods are affected first since they are in the outer portion of the retina and are easily triggered by things such as dimmed light. Mild symptoms of RP sometimes appear during childhood, usually at around age 10. Typically, severe vision problems do not develop until early adulthood. Symptoms of RP can include:
- Decreased vision at night or in low light (this symptom usually occurs first)
- Loss of peripheral vision, causing ‘tunnel vision’
- Loss of central vision (usually found in severe cases)
What Causes Retinitis Pigmentosa?
Unfortunately, not all cases can be linked to heredity, leaving a big question mark around the actual cause of retinitis pigmentosa. However, most cases are linked to genetic mutations inherited from one or both parents. Genetic mutations can be passed from parent to child one of three ways: autosomal recessive, autosomal dominant, or X-linked. In autosomal recessive RP, parents who carry the gene but have no symptoms may affect one or more of their children. Autosomal dominant RP is similar, in that an affected parent could have affected and unaffected children. In families with X-linked RP, only males are found to be affected, even though females can carry the gene.
Diagnosing Retinitis Pigmentosa
If a family member of yours has RP, it is highly recommended that you and your entire family get regular eye exams. If RP is suspected, diagnostic testing may include:
- Color vision
- Examination of your retina (pupils are dilated by special eye drops)
- Intraocular pressure is measured
- Side vision test (visual field test)
- Visual acuity test
- Slit lamp examination
- Retinal photography
- Pupil reflex response
- Fluorescein angiography
- Measurement of the electrical activity in retina (electroretinogram)
- Refraction test
Retinitis Pigmentosa Treatment
Unfortunately, there is no effective treatment for this progressive disease, although studies are being conducted to try to find new treatment options. Antioxidants such as Vitamin A palmitate are known to slow down RP, but taking large doses of Vitamin A can potentially damage one’s liver, so the risks and benefits of vitamin A should be weighed carefully with your eye care professional. Other clinical studies are being done with omega-3 fatty acid DHA. Many eye care professionals recommend wearing U.V. protection sunglasses to help protect the retina from ultraviolet light. This may also help preserve your vision.
An implantable microchip is also being studied and developed to help enhance the retina’s functionality. Although treatment for RP is limited, there are low-vision aids that can help you maintain your independence. Optical, electronic, mechanical, and computer-based low-vision products are available. Talk with your eye care professional or a low-vision specialist about what products may work for you. Again, this eye disease is a slow, progressive one that rarely causes complete blindness with early detection, a proper diagnosis, and effective low vision aids.
Complications of Retinitis Pigmentosa
Some people with RP are known to develop cataracts at an early age, while others experience a swelling of the retina (macular edema). Fortunately, cataracts can be removed to preserve vision. The progression of the disease varies from person to person. Complications may include:
- Loss of central or peripheral vision
- The gene can be passed on to children
- Trouble driving at night
- May need visual aid for the remainder of life
- Visual aids may not be effective
Preventing Retinitis Pigmentosa
Currently, there is no way to effectively prevent this disease. If you are a parent with the disease, you should have your children’s eyes examined often so the disease can be detected early and serious complications can be prevented.
Talking to Your Eye Doctor
Here are some questions to ask your eye care professional about retinitis pigmentosa:
- Do you know of a low vision specialist in the area?
- What are the chances I will lose my vision in the future?
- If initial treatment options do not work, what steps will we take?
- How often will I need to schedule follow-up visits with you?
- What should I expect during my follow-up visits?
- What else can I do to prevent this condition from worsening?
- How much vitamin A and zinc should I include in my daily diet?
- RP International – Serving the Visually Impaired, 2011 http://rpinternational.org
- J. Weizer, MD, J. Stein, MD, MS “Reader’s Digest Guide to Eye Care” (Quantum Publishing Ltd 2009)13-14; 122
- J. Anshel “Smart Medicine for Your Eyes” (SquareOne Publishers, 2011) 305-307; 400