Retinitis Pigmentosa

 

Cataracte

Definition

Retinitis pigmentosa (RP) is a group of genetic disorders that affect the retina’s ability to respond to light. This inherited disease causes a slow loss of vision, beginning with decreased night vision and loss of peripheral (side) vision. Eventually, blindness results. Unfortunately, there is no cure for RP.

The retina is the layer of light-sensing cells lining the back of your eye that converts light rays into nerve impulses. The impulses are sent through the optic nerve to your brain, where they are recognized as images.

With RP, cells in the retina called rods and cones die. With most forms of RP, rods — which are mainly in the outer regions of the retina and are responsible for our peripheral and night vision — degenerate first. When the retina’s more centrally-located cones are affected, the result is loss of color perception and central (reading) vision. 

Source : AAO

 

Organ

The organ affected by retinitis pigmentosa is the retina.

 

Symptoms

Symptoms often first appear in childhood. However, severe vision problems do not often develop before early adulthood.

  • Decreased vision at night or in low light. Early signs may include having a harder time moving around in the dark.
  • Loss of side (peripheral) vision, causing "tunnel vision."
  • Loss of central vision (in advanced cases). This will affect the ability to read.

Source : Medline Plus 

 

Frequency

Prevalence in all ages is approximately 1 in 4,000 and, in the age group 45 to 64 years, 1 in 3,195. 

There are no geographical or sex predilections. However, because of X-linked varieties, men may be affected slightly more than women.

Source : Patient 

 

Causes

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. 

Source : Medicinenet

 

Evolution

The disorder will continue to progress slowly. Complete blindness is uncommon.

Peripheral and central loss of vision will occur over time.

People with retinitis pigmentosa often develop cataracts at an early age. They may also develop swelling of the retina (macular edema). Cataracts can be removed if they contribute to vision loss.

Source : Medline Plus 

 

Prevention

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.

 

What research is being done for retinitis pigmentosa?

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. 

Source : Medicinenet

 

Diagnosis

If you have poor night vision or a loss of side vision, or if there is a history of retinitis pigmentosa in your family, your ophthalmologist will conduct a comprehensive eye exam to determine if you have retinitis pigmentosa. Your ophthalmologist will dilate your eyes to look at the back of them for signs of disease.

Your ophthalmologist may use an electroretinogram to help diagnose retinitis pigmentosa. This is where electrodes are painlessly placed on the cornea (the clear front window of the eye) and around the eye to measure how retinal cells respond to flashes of light. The results will show if the cells are responding properly.

Another test your ophthalmologist may use in diagnosing RP is a visual field test (see photo). In this procedure, you look at a fixed point and then signal when an object appears in your side vision.

Source : AAO 

 

Treatment

There is no effective treatment for this condition. Wearing sunglasses to protect the retina from ultraviolet light may help preserve vision.

Some studies suggest that treatment with antioxidants (such as high doses of vitamin A palmitate) may slow the disease. However, taking high doses of vitamin A can cause serious liver problems. The benefit of treatment has to be weighed against risks to the liver.

Clinical trials are in progress to assess new treatments for retinitis pigmentosa, including the use of DHA, which is an omega-3 fatty acid.

Other treatments, such as microchip implants into the retina that act like a microscopic video camera, are in the early stages of development. These treatments may be useful for treating blindness associated with RP and other serious eye conditions.

A vision specialist can help you adapt to vision loss. Make regular visits to an eye care specialist, who can detect cataracts or retinal swelling. Both of these problems can be treated.

Source : Medline Plus

 

Images

  Fundus of patient with retinitis pigmentosa, mid stage

Fundus of patient with retinitis pigmentosa, mid stage

SourceBy Christian Hamel (Retinitis pigmentosa by Christian Hamel) [CC BY 2.0], via Wikimedia Commons

 

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