Retinitis Pigmentosa

• Retinitis pigmentosa is a bilateral inherited condition that involves both eyes.
• It usually starts later in life and progresses to blindness.
• Low-vision rehabilitation provides some help in coping with the condition, but there is no treatment or cure at this time.

Retinitis pigmentosa is the most common of a group of hereditary progressive retinal degenerations or dystrophies. There is considerable variation and overlap among the various forms of retinitis pigmentosa. Common to all of them is progressive degeneration of the retina, specifically of the light receptors, known as the rods and cones. The rods of the retina are involved earlier in the course of the disease, and cone deterioration occurs later. In this progressive degeneration of the retina, the peripheral vision slowly constricts and central vision is usually retained until late in the disease.

Retinitis pigmentosa is an inherited condition which involves both eyes. If it starts in one eye, the other eye usually develops the same condition in a number of years. Most cases are familial, inherited in a variety of ways, including dominant, recessive, and sex-linked recessive. Some cases are sporadic and lack a family history of the disease. A thorough genetic pedigree, often with the aid of a genetic counselor, is essential in determining risk of future generations acquiring the disease.

Retinitis pigmentosa is usually diagnosed during the teenage years but may be present at birth. The latter congenital type is usually fairly stable and nonprogressive. Cases that are diagnosed later in life are often milder and may progress more slowly.

RP is sometimes associated with other systemic illnesses. Usher syndrome, characterized by retinitis pigmentosa and neural hearing loss, is the most common cause of deaf-blindness in the United States. The hearing loss usually is diagnosed earlier than the eye changes.

Since retinitis pigmentosa begins as rod degeneration, the patient first notices increasing difficulty in night vision, followed by difficulty seeing in the periphery. Slowly progressive constriction of the visual field leads to tunnel vision. A small area of central vision in both eyes usually persists for years. Generally night blindness precedes tunnel vision by years or even decades. Total blindness eventually ensues in most cases. The age of appearance of legal blindness ranges from as early as childhood to as late as the 40s.

• Decreased vision at night or in low light
• Loss of side (peripheral) vision
• Loss of central vision (in advanced cases)

Although the history (especially the possibility of retinitis pigmentosa appearing in other family members) and complaints of the patient may make one suspect RP, it is primarily diagnosed by examination. The patient may complain of difficulty seeing at night or in low light condition. At some point, the ophthalmologist observes relatively characteristic clumping of pigment in the retina in a pattern described as resembling bone spicules. Fundus examination (looking at the back layers of the eye with the ophthalmoscope, an instrument allowing the visualization of the back of the eye by looking through the pupil) affords the view of the retina. A similar pattern may appear in congenital syphilis which is unrelated and must be distinguished.

Two tests are essential in the diagnosis and the follow-up exams.

Visual field testing will find defects in the peripheral (side vision) with the degree of loss related to defects in relation to the damage occurring in this disease. Over time, the visual field may reduce to a small central island of vision causing "tunnel vision." The final progression may be the complete loss of the remaining central vision.

Electrophysiological testing by the ophthalmologist (often by referral to a university ophthalmology department, since very few private offices would have this equipment) is often diagnostic. Responses to flashes of light are measured via electrodes placed on the surface of the eye. It is a painless test. The electroretinogram (ERG), in conjunction with the visual field exam, will usually make the diagnosis. This will also determine if there is any cone involvement.

Recently, gene testing for defects is being done to clarify the basic cause for RP and assist in ultimately finding a treatment.

As of now there is no specific cure for retinitis pigmentosa. For years, vitamin A therapy has been recommended for many RP patients, based on research dating back to the early 1990s. A randomized, controlled trial of vitamins A and E found that 15,000 IU a day of vitamin A palmitate could slow the course of the condition among adults with typical forms of RP. Vitamin E, however, at a 400 IU a day dose appeared to have an adverse effect on the course of RP in the same study.

Another study among adult patients with RP has shown that an omega-3-rich diet containing docosahexaenoic acid can further slow disease progression. Such a diet includes one to two 3-ounce servings per week of oily fish such as salmon, tuna, herring, mackerel, or sardines. Researchers estimated that the combination of vitamin A plus this diet could provide almost 20 additional years of useful vision for adults who start the regimen in their 30s.

Serious research is being carried out with some progress being made in experiments in rats. (An international research team led by Columbia University Medical Center successfully used mouse embryonic stem cells to replace diseased retinal cells and restore sight in a mouse model of retinitis pigmentosa.)

It is important to make a diagnosis so that the patient and family may be counseled as to the status of the disease, what the patient may do, and what low-vision treatments (in more advanced disease) might be available to allow maximization of the patient's visual potential.

Low-vision services will be very helpful in coping with the disease. This low-vision therapy may be provided in the eye specialists' offices or by referral to a low-vision center.

As the visual field constricts, efforts are being explored for the use of visual field expanding glasses.

If cataracts occur, they may be removed as in other patients with cataracts, usually with the use of an intraocular lens.

It lasts a lifetime, with blindness often occurring if one lives long enough.

Cataracts occur at a higher incidence in RP patients. If the cataracts are significant, cataract removal can be performed surgically. When cataracts occur, patients respond well to cataract removal with implantation of an intraocular lens. However, this does not improve retinal function.

The ultimate complication of RP is blindness from loss of retinal function.

The prognosis is poor since there is no cure for the disease. However, there are researchers working hard on this disease. Significant progress is being made, and there is reason for optimism that the near future will bring treatment which may stabilize the disease, prevent it, or both.

There is a large amount of research currently being performed both in the United States and internationally. As we acquire more knowledge about influencing gene function, treatment for hereditary diseases, including RP, will become available. If as few as 5% of cones can be kept alive, a person with RP can continue to function independently.

A promising treatment aimed at preserving cones, the retinal cells that provide central and daytime vision, is in a phase I clinical trial. This involves a protein known as rod-derived cone viability factor (RdCVF). It has preserved vision in several preclinical studies.

Other promising research involves synthetic nucleic acid nanoparticles, growth factors such as ciliary neurotrophic factor, gene therapy with recombinant adeno-associated virus, and stem cell therapy. Scientists and ophthalmologists are also investigating retinal transplants and artificial retinal implants.

The American Academy of Ophthalmology

National Association for Visually Handicapped
22 West 21st Street
New York, NY 10010
Tel: 212-889-3141
Fax: 212-727-2931
Email: staff@navh.org

NIH/National Eye Institute
Building 31 Rm 6A32
31 Center Dr MSC 2510
Bethesda, MD 20892-2510
Tel: 301-496-5248
Fax: 301-402-1065
Email: 2020@nei.nih.gov

"Retinitis Pigmentosa," National Institutes of Health, Office of Rare Diseases Research

Retinitis Pigmentosa International
PO Box 900
Woodland Hills, CA 91365
Tel: 818-992-0500
Fax: 818-992-3265
Tel: 800-344-4877
Email: info@international.org

Foundation Fighting Blindness
11435 Cronhill Drive
Owings Mills, MD 21117-2220
Tel: 410-568-0150
Fax: 410-363-2393
Tel: 800-683-5555
TDD: 800-683-5551
Email: info@blindness.org

National Association for Parents of Children With Visual Impairments (NAPVI)
PO Box 317
Watertown, MA 02472
Tel: 617-972-7441
Fax: 617-972-7444
Tel: 800-562-6265
Email: napvi@perkins.org

American Foundation for the Blind
11 Penn Plaza Suite 300
New York, NY 10001
Tel: 212-502-7600
Fax: 212-502-7777
Tel: 800-232-5463
TDD: 212-502-7662
Email: afbinfo@afb.org

Council of Families Wth Visual Impairment
1155 15th St. NW, Suite 1004
Washington, DC 20005
Tel: 202-465-5081
Fax: 202-465-5085
Email: info@acb.org

American Printing House for the Blind
1839 Frankfort Avenue
PO Box 6085
Louisville, KY 40206-0085
Tel: 502-895-2405
Fax: 502-899-2274
Tel: 800-223-1839
Email: info@aph.org

Recording for the Blind, Inc.
545 Fifth Avenue Suite 1005
New York, NY 10017
Tel: 800-221-4792

MUMS (Mothers United for Moral Support, Inc.) National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
Tel: 920-336-5333
Fax: 920-339-0995
Tel: 877-336-5333
Email: mums@netnet.net

Foundation Fighting Blindness (Canada)
60 St. Clair Ave East Suite 703
Toronto, Ontario, M4T 1N5
Canada
Tel: 416-360-4200
Fax: 416-360-0060
Tel: 800-461-3331
Email: info@ffb.ca

Retina International
Ausstellungsstrasse 36
CH-8005
Zürich, Switzerland
Tel: 0-44-444-10-77
Fax: 0-44-444-10-70
Email: c.fasser@e-link.ch