About retinitis pigmentosa

What is retinitis pigmentosa?

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.



What are the symptoms for retinitis pigmentosa?

Retinitis pigmentosa usually starts in childhood. But exactly when it starts and how quickly it gets worse varies from person to person. Most people with RP lose much of their sight by early adulthood. Then by age 40, they are often legally blind.

Because rods are usually affected first, the first symptom you may notice is that it takes longer to adjust to darkness (called “night blindness). For example, you may notice it when you walk from bright sunshine into a dimly lit theater. You may trip over objects in the dark or not be able to drive at night.

You may lose your peripheral vision at the same time or soon after your night vision declines. You may get "tunnel vision," which means you can’t see things to the side without turning your head.

In later stages, your cones may be affected. That will make it harder for you to do detail work, and you may have Trouble seeing colors. It’s rare, but sometimes the cones die first.

You might find bright lights uncomfortable -- a symptom your doctor may call photophobia. You also may start to see flashes of light that shimmer or blink. This is called photopsia.



What are the causes for retinitis pigmentosa?

More than 60 different genes can cause the different types of retinitis pigmentosa. Parents can pass the problem genes on to their children in three different ways:

Autosomal recessive RP: Each parent has one problem copy and one normal copy of the gene that's responsible, but they don’t have any symptoms. A child that inherits two problem copies of the gene (one from each parent) will develop this type of retinitis pigmentosa. Since two copies of the problem gene are needed, each child in the family has a 25% chance of being affected.

Autosomal dominant RP: This type of retinitis pigmentosa requires only one copy of the problem gene to develop. A parent with that gene has a 50% chance of passing it to each child.

X-linked RP: A mother who carries the problem gene can pass it down to their children. Each one of them has a 50% chance of getting it. Most women who carry the gene won’t have any symptoms. But about 1 out of every 5 will have mild symptoms. Most men who get it will have more severe cases.



What are the treatments for retinitis pigmentosa?

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.



What are the risk factors for retinitis pigmentosa?

Retinitis pigmentosa (RP), also called hereditary retinal dystrophy, is the most common form of retinopathy. 70 to 80 % of the cases are non-syndromic, in which the patient only loses vision. On the other hand, syndromic patients suffer from systemic involvement in addition to visual impairment. Generally, the initial symptom is loss of night vision. As the disease progresses, the visual field narrows gradually. Eventually, it leads to total loss of vision. Other impairments include loss of accurate color discrimination and visual acuity.

Risk factors
1. RP is a hereditary disease caused by mutations in the genes involved in the biochemical mechanisms of rod photoreceptors in the retina. They initially cause dysfunction of rods and then apoptosis. As the disease progresses, the cone cells also die.
2. The causative mutations have been identified on more than 100 loci in 50 different genes. They follow multiple patterns of inheritance, namely autosomal recessive, X-linked, and autosomal dominant manner.
3. Genetic predisposition: Familial history of the condition is the major risk factor. Among the autosomal mutations, dominant is more deadly than recessive. Whereas males are prone to X-linked inheritance due to the lack of counter alleles against a single X-chromosome.
4. Gender: Males are more likely to suffer sporadic RP compared to females.

Symptoms
Loss of night vision, progressive narrowing of visual field,Loss of accurate color discrimination and visual acuity
Conditions
Retinopathy
Drugs
Vitamin A supplementation



Is there a cure/medications for retinitis pigmentosa?

Retinitis pigmentosa, also called hereditary retinal dystrophy, is a group of retinopathies that produces progressive loss of vision. Worldwide, it is the most common disease of the retina with an incidence rate of one in 5000 individuals. It presents a wide variety of clinical manifestations. Generally, the first symptom is nyctalopia, loss of night vision. The disease that causes vision loss alone is called non-syndromic RP. Other features include loss of accurate color discrimination and loss of visual acuity. Followed by loss of night vision, the visual field narrows down over time. Most patients may perceive light even in the late stages.

Treatment
1. For many years, vitamin A supplementation has been the most recommended treatment. Studies have shown that vitamin A slows down the deterioration of the retina. Precautionary monitoring of the liver during high-dose supplementation is necessary.
2. Many electronic retinal implants are available. They promise to restore partial vision in patients with end-stage RP. The method has challenges, such as complicated issues for rehabilitation management of the patients and functional longevity.
3. Gene augmentation therapy that targets restoration of normal gene expression in photoreceptors is under development. Another prospective treatment is cell replacement therapy which involves transplanting retinal progenitor cells into the eye.

Symptoms
Loss of night vision, progressive narrowing of visual field,Loss of accurate color discrimination and visual acuity
Conditions
Retinopathy
Drugs
Vitamin A supplementation



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