Retinitis Pigmentosa

Excerpt

The name retinitis pigmentosa (RP), described initially as a clinical entity in 1853, was not attached to the disease until 1857. Considered by most to be a misnomer, the term retinitis persists today, even though inflammation plays only a small role in the natural progression of the disease. RP is not a single entity but rather a group of disorders that produce a gradual loss of vision. Also known as hereditary retinal dystrophy, it affects 1 in every 4000 people in the United States and approximately one in 5000 worldwide, making RP the most common inherited disease of the retina. RP is usually bilateral; however, there have been reports of unilateral eye involvement with this condition. While it may present and progress with a variety of clinical manifestations, the first symptom of RP is generally nyctalopia, or loss of night vision, followed by a gradual narrowing of the visual fields. Over time, depending on the severity and rate of progression of the disease, tunnel vision or complete vision loss can result. As the disease progresses, other features may also develop, including loss of accurate color discrimination and eventual loss of visual acuity. Most patients will maintain some light perception even with late-stage RP as the macula continues functioning. Perhaps the most unsettling late effect of RP is the development of photopsia (perceived flashes of light), likely due to sensory deprivation that can progress to the point of visual hallucinations.

The disease may involve vision loss alone, referred to as "nonsyndromic" RP. About 70% to 80% of RP cases fall into the nonsyndromic category. When RP occurs in conjunction with systemic disease, it is termed "syndromic" RP. The most common form of syndromic RP is Usher syndrome, which involves neurosensory hearing loss associated with vision loss.