Retinitis pigmentosa is a group of hereditary, progressive retinal degenerations or dystrophies. There are a lot of variations between the different forms of retinitis pigmentosa, but what they all have in common is progressive degeneration of light receptors, also known as the rods and cones as a part of the retina. By nature, RP is progressive degeneration of the retina (photoreceptor cells detecting light), which leads to the constriction of peripheral vision. RP is considered a rare disease: It affects roughly 1 in 4,000 men and women of all ages, races, cultures and ethnic backgrounds worldwide.
Retinitis Pigmentosa cannot be caused by injury, infection or any other external or environmental factors. It is an inherited disorder caused by pathological changes in one of more than 50 genes. Different kinds of gene mutations lead to damage of the photoreceptors. The first signs of RP can be observed by the doctor in affected children as early as age 10 or even at birth. If RP is diagnosed later in life, it is milder and may progress more slowly.
Most cases are inherited and fall into three main categories: autosomal recessive, autosomal dominant, and X-linked recessive. The main difference is how high the risk is of passing the gene to the child. Some RP cases have no previous family history. The cause of such cases cannot be explained.
Retinitis Pigmentosa can be diagnosed during routine eye examination if there are abnormal, dark pigment deposits in the retina. Also the following examinations are important: a) Typical and progressive complaints of night blindness and peripheral visual field defects; b) Visual field testing finds defects in the peripheral (side vision) with the degree of loss related to defects in relation to the damage occurring in this disease; c) Optical Coherence Tomography (OCT), which shows the loss of photoreceptors on the retina.
RP suspicion must be confirmed with:
Electroretinogram (ERG) measures the electrical activity of photoreceptor cells, which is decreased (rather than absent) if a person suffers RP.
Genetic subtyping: Definitive test for diagnosis to identify the particular defect. With help of genetic testing, a patient can learn about the progression of his particular form of the disorder.
There are many other mostly genetic retinal degenerations with their own distinct characteristics similar to RP. More known syndromes are:
1. Bardet-Biedl Syndrome. The most common are RP, extra fingers and/or toes, obesity, mental retardation and kidney disease.
2. Usher Syndrome. The combination of RP with congenital hearing deficit and problems with balance (Type II)
3. Bassen-Kornzweig Syndrome. RP combines with severe and progressive neurologic problems.
4. Choroideremia has symptoms similar to RP, including night blindness followed by loss of peripheral vision. It is characterized by degeneration of the retina and of the choroid.
5. Gyrate Atrophy. This retinal degenerative disease is associated with myopia, night blindness, reduction in peripheral vision and cataracts
6. Retinoschisis. Juvenile retinoschisis is characterized by vision loss that is usually diagnosed in childhood.
7. Refsum’s Syndrome. RP with peripheral neuropathy, cerebellar ataxia
8. Alstrom Syndrome. RP with Obesity, Deafness, Diabetes and cardiac complaints
9. NARP Synrome. RP with Neuropathy and Ataxia
10. Kearns Sayre Syndrome. RP with external ophthalmoplegia and complete heart block
A common feature of almost all forms of Retinitis Pigmentos is gradual loss of vision, but to predict the rate of loss is not possible, even for relatives. Vision sometimes appears to remain stable between annual eye examinations. The disease is incurable. However, a lot of progress in the research has been made. Nowadays, vision deterioration can be slowed down significantly, which gives hope that RP may be stabilized or prevented in the near future.
A number of drugs have been proposed for the management, but the evidence supporting their effectiveness is variable and generally limited.
Referral to a low-vision specialist is very helpful.
1. Patients should regularly visit an eye care specialist for examinations and treatment of any ocular complications such as cataracts, glaucoma and cystoid macular edema.
2. Patients should use sunglasses to protect the retina from ultraviolet light. Bright light can damage the epithelium.
3. It is important to receive genetic consulting and have all the family members (siblings and offspring) examined for evidence of RP.
4. General consulting by experienced staff is essential. It is worth mentioning that most children have enough sight to complete their education in normal schools.
5. It is legally required that the RP patient must inform the services responsible for providing a driver's license about his medical condition and do a specialized visual field test, which is carried out by specially approved optometrists.
6. The patient should register for severe sight impairment or for sight impairment.
The symptoms usually become apparent between the ages of 10 and 30, although some changes may become apparent in early childhood.
Children often have difficulty adjusting to changes in lighting or getting around in the dark (nyctalopia). People with retinitis pigmentosa often suffer from photophobia, finding bright lights uncomfortable.
Progressive loss of peripheral vision is common, although there may be loss of central vision which tends to occur later. This results in impaired sight at a variable rate.
Slow constriction of the visual fields leads to tunnel vision, which significantly lowers patients’ quality of life, and eventually total blindness.
The age of appearance of legal blindness ranges from childhood to the 40s, but symptoms may progress at different rates even in members of the same family.
Other forms of Retinitis Pigmentosa first affect central vision, which cannot be corrected with glasses or contact lenses.
Patients can experience disturbances in color perception. As the disease progresses, rod cells degeneration leads to night blindness and peripheral vision loss.
There are many practical issues visually impaired patients with Retinitis Pigmentosa are looking for. Even though RP is a progressive disease, people wonder what else can negatively affect their vision. Below, you will find answers to the most frequently asked questions regarding RP:
- Does exposure to light lead to loss of vision for people with RP?
- Can people with RP drive?
- Does pregnancy have an effect on RP?
- What is the likelihood that I will pass the RP gene on to my children?
- What should I do if my child is diagnosed with RP?
It has been reported that some women have experienced more rapid progression of retinitis pigmentosa during pregnancy, but it is problematic to study the issue thoroughly because RP is rare. If a woman is pregnant or is planning to get pregnant, she should make sure that her ophthalmologist knows about her pregnancy and her gynecologist is aware of her vision problems.
A lot of people with retinitis pigmentosa drive legally with no problems, but legal vision requirements vary from country to country. That is why an RP patient should discuss the issue with his eye care professional. There are several, main criteria that affect driving, such as visual acuity, extent of visual field loss, binocular field of vision, and diplopia (double vision).
The issue about the inheritance pattern of retinitis pigmentosa in the family should be discussed with a genetic specialist. An eye care professional specializing in hereditary retinal degenerations can help to explain how the RP gene is inherited in a particular family and what the chance is of its further inheritance.
If you child is diagnosed with retinitis pigmentosa, his or her case should be evaluated by a low-vision specialist as soon as possible. School administration and teachers should also be warned of his or her medical condition. Nowadays, there are a lot of low-vision aids that help to maximize existing vision. For example, there are special lenses that magnify central vision to expand the visual field and eliminate glare and to help with computer programs, reading the text, portable lightning devices, and adjusting a dark environment. It is also important to have regular eye examinations.
Nowadays, there are quite a number of services helping people with retinitis pigmentosa to conduct their daily business of living: from transportation to housekeeping. Such services teach how to orient and travel with a white cane or a dog guide and inform about control of illumination and contrast along with special lenses. With advancing technology, many assistive devices appear, becoming more and more sophisticated and helpful for people with RP. They include closed-circuit televisions (CCTV), reading machines, and different computer programs that allow bigger type on screen or provide braille the version of what the screen shows.
Also, there are optical devices that maximize usable vision: eyeglasses, prisms, telescopes and night vision aids, which can be a useful way to scan surroundings and find one's bearings.
With the exception of vitamin A palmitate, there are currently no drugs available to actually treat people with retinitis pigmentosa. Work by scientists around the country is beginning to lay the foundation for the development of pharmaceutical agents that one day might alleviate or prevent the symptoms of RP.
Several drug treatments have been proposed to slow down progression of RP. These following treatments are known as hyperbaric oxygen delivery, topical brimonidine tartrate, vitamins, docosahexaenoic acid, gangliosides, lutein, oral nilvadipine, ciliary neurotrophic factor, and valproic acid. All treatment seems to be safe, but did not show significant benefit on visual function. Although all medical treatments for RP appear safe, evidence of effectiveness is limited.
Important! Please note that:
Some practitioners also consider vitamin A as a possible treatment option to slow down the progression of retinitis pigmentosa. Research suggests taking high doses of vitamin A (15,000 IU/day) may slow progression a little in some people, but the results are not strong enough. Taking too much vitamin A can be toxic, and the effects of vitamin A on the disease are relatively weak. Talk to an eye care professional to determine if taking vitamin A is right for you or your child.
Since retinitis pigmentosa is usually the result of a defective gene, gene therapy has become a widely explored area for future research. The goal of such research would be to discover ways healthy genes can be inserted into the retina.
Gene therapy is based on simple logic: If a gene is defective, replace it with one that is not defective. While this may sound simple, the actual procedure of gene therapy is very complex. There are a number of reasons why RP is a disease particularly suited to the use of gene therapy. First and foremost, some of the defective genes have been identified. Also, there are a number of applicable animal models in which gene therapy can be tested for effectiveness and safety. While all of the above factors make gene therapy a promising future approach for treating RP, there are still many obstacles remaining. One key question is how to actually introduce the healthy gene into diseased cells. In laboratory experiments, researchers have found that a neutralized virus can transport a healthy gene to degenerating photoreceptor cells. This viral delivery method must be made safe and effective before gene therapy can be tested in humans.
Retinal prosthesis is also an important area of exploration because the prosthesis, a man-made device intended to replace a damaged body part, can be designed to take over the function of the lost photoreceptors.
An artificial vision device called the Argus II has also shown promise for restoring some vision to people with late-stage retinitis pigmentosa. The Argus II is a prosthetic device that functions in place of lost photoreceptor cells. It consists of a light-sensitive electrode that is surgically implanted on the retina. A pair of glasses with a camera wirelessly transmits signals to the electrode that are then relayed to the brain. Although it does not restore normal vision, in clinical studies, the Argus II enabled people with RP to read large letters and navigate environments without the use of a cane or guide dog. The Argus II device has not proven effective, but the FDA has determined that its probable benefits outweigh its risks to health.
One should understand that vitamin A palmitate is not a cure for retinitis pigmentosa, that can improve your vision. There has been some evidence that the higher dose of it can possibly make this degenerative process slower.
People with very advanced RP are not recommended to take vitamin A, but in case of non-advanced stages of RP, slowing could mean additional years of useful vision.
However, there are some warnings that accompany this recommendation. Though it occurs rarely, patients should have a pretreatment assessment of fasting serum vitamin A levels and liver function and annually thereafter. High doses of vitamin A (15,000 IU/day) are not recommended for pregnant women or women planning pregnancy. Older adults should consult with their physicians about their bone health due to the fact that long-term vitamin A supplementation affects bone density. Vitamin A is contraindicated for patients with renal failure or renal transplant, because of excessive renal re-absorption, and to patients taking doxycycline, since the combination can cause increased intracranial pressure.
Important! retinitis pigmentosa patients under the age of 18 were not evaluated, and 15,000 IU of supplementary vitamin A palmitate is not recommended for them and must be discussed with an eye care specialist.
Vitamin E has the opposite effect of vitamin A: Clinical studies have shown that people taking 400 IU daily of vitamin E have a faster rate of retinal degeneration than those who do not take any. Thus, it's recommended that people with retinitis pigmentosa should avoid high doses of vitamin E supplements. However, there is no evidence that small supplemental amounts of vitamin E lead to any progression of RP.
Besides vitamin A, there is also an omega-3 rich diet, which has been suggested to slow down the process of vision loss. Omega-3 can be found in oily fish such as tuna, salmon and herring.
Further sources of vitamin A include: carrots, butter, cheese, milk, cod liver oil, apricots and egg yolks.