Junior Blind of America

 

Definition:
Retinitis Pigmentosa (RP) is a degeneration of the retina, resulting in decreased night vision, a gradual loss of peripheral (side) vision, and in come cases, loss of central vision. The degeneration progresses over time and can lead to total blindness. RP is a rare, inherited disease for which there is as yet no treatment or cure. It is a genetic condition that can be inherited in various forms of transmittance but there are also many spontaneous cases of RP where there are no family members with this progressive disease. The retina is the light sensing tissue that lines the internal surface of the eye. It consists of millions of rod cells and cone cells. The cone cells are located in the central region of the retina and are responsible for detailed sight, color vision, and vision during the daylight. In contrast, the rod cells are lined on the periphery (side) of the retina and provide peripheral (side) vision, night vision, and visual clues for walking. RP affects a region of the rod and cone cells called the outer segments. The outer segments tend to accumulate too much metabolic waste, which is normally disposed of. Consequently, the retina appears pigmented with clumps of pigment. As the debris accumulates, the function of the rod and cone cells deteriorates.

Cause:
Retinitis pigmentosa is an inherited disorder, and therefore not caused by injury, infection or any other external or environmental factors. People suffering from RP are born with the disorder already programmed into their cells. Doctors can see the first signs of retinitis pigmentosa in affected children as early as age 10. Research suggests that several different types of gene mutations (changes in genes) can send faulty messages to the retinal cells which leads to their progressive degeneration. In most cases, the disorder is linked to a recessive gene, a gene that must be inherited from both parents in order to cause the disease. But dominant genes and genes on the X chromosome also have been linked to retinitis pigmentosa. In these cases, only one parent has passed the disease gene. In some cases, a new mutation causes the disease to occur in a person who does not have a family history of the disease. The disorder also can show up as part of other syndromes, such as Bassen-Kornzweig disease or Kearns-Sayre syndrome.

Characteristics:
As the disease progresses and more rod cells breakdown, patients lose their peripheral vision (tunnel vision). Individuals with RP often experience a ring of vision loss in their periphery, but retain clear central vision. Others report the sensation of tunnel vision, as though they see the world through a straw. Many patients with retinitis pigmentosa retain a small degree of central vision throughout their life. Other forms of RP, sometimes called cone-rod dystrophy, first affect central vision. Patients first experience a loss of central vision that cannot be corrected with glasses or contact lenses. With the loss of cone cells also comes disturbances in color perception. As the disease progresses, rod cells degenerate causing night blindness and peripheral vision. Symptoms of RP are most often recognized in children, adolescents and young adults, with progression of the disease. The following are the most common symptoms. However, each individual may experience symptoms differently, especially with severity and progression as the most obvious variables. Some persons with RP experience a slow, very progressive loss of vision, while others lose their visual ability much more quickly and severely. Other common symptoms may include:

• difficulty seeing in poor light (i.e., at dusk or in a dimly lit area) or in the dark
• a diminished visual field, either central vision (a condition called macular dystrophy) or peripheral vision (sometimes referred to as tunnel vision)
• difficulty reading print (with a loss of central vision)
• difficulty deciphering detailed images (with a loss of central vision)
• difficulty with stumbling or tripping over objects not seen; clumsiness (with a loss of peripheral vision)
• glare

 

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