Definition:
Retinitis pigmentosa (RP) pertains to a group of genetic eye conditions characterized by progressive night blindness preceded by an extended period of tunnel vision. In retinitis pigmentosa, abnormalities of the photoreceptors or the presence of retinal pigment epithelium (RPE) cause progressive visual loss in affected patients.
Diagnosis:
Retinitis pigmentosa can be diagnosed through visual field testing and electroretinography (ERG), which document progressive loss in photoreceptor function. Family history can be used to determine the mode of inheritance for the disorder. DNA testing is also recommended.
Treatment:
To date, there is no proven medical treatment available to completely cure retinitis pigmentosa. However, the progression of the disorder can be controlled with 15000 IU of vitamin A palmitate medication.
Researchers continue to seek other modes of treatment for RP. Proposed therapies include artificial retinal implants, stem cells, gene therapy, drug therapies, and nutritional supplements.
Symptoms and Signs:
Retinitis pigmentosa initially presents as a defective dark adaptation or night blindness (nyctalopia) preceded by years or decades of tunnel vision. These initial signs are followed by the constriction of the peripheral visual field and eventually, in later stages, loss of central vision.
The progression of retinitis pigmentosa varies in every case. In some cases, affected individuals do not become blind until they reach their 40s or 50s and even retain some of their sight in their lifetimes. However, most patients go completely blind from retinitis pigmentosa. In some cases, blindness occurs as early as childhood.
Causes:
The mutation of the gene rhodopsin, a pigment that plays a central role in the visual transduction cascade, is believed to be the cause of retinitis pigmentosa. A number of varied mutations have been found in rhodopsin, accounting for a percentage of all types of retinal degeneration. Most of these mutations are inherited mostly in a dominant pattern.
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