Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visual field). As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.Retinitis pigmentosa is generally inherited from one or both parents or rarely it can be newly evolved from a miscoding during DNA division. It is caused by genetic miscoding of proteins in one of more than 300 genes involved. The underlying mechanism involves the progressive loss of rod photoreceptor cells that line the retina of the eyeball. The rod cells secrete a neuroprotective substance (Rod-derived cone viability factor, RdCVF) that protects the cone cells from apoptosis (cell death). However, when the rod cells die, this substance is no longer provided. This is generally followed by the loss of cone photoreceptor cells. Diagnosis is by eye examination of the retina finding dark pigment deposits caused by the rupture of the underlying retinal pigmented epithelial cells, given that these cells contain a pigment known as melanin. Other supportive testing may include the electroretinogram (ERG), visual field testing (VFT), ocular coherence tomography (OCT) and DNA testing to determine the gene responsible for a persons particular type of RP (now called Inherited Retinal Dystrophy (IRD).There is currently no cure for retinitis pigmentosa. Efforts to manage the problem may include the use of low vision aids, portable lighting, or orientation and mobility training.
Combined with cross-sectional imagery of optical coherence tomography, which provides clues into photoreceptor thickness, retinal layer morphology, and retinal pigment epithelium physiology, fundus imagery can help determine the state of RP progression.While visual field and acuity test results combined with retinal imagery support the diagnosis of retinitis pigmentosa, additional testing is necessary to confirm other pathological features of this disease. Electroretinography (ERG) confirms the RP diagnosis by evaluating functional aspects associated with photoreceptor degeneration, and can detect physiological abnormalities before the initial manifestation of symptoms. An electrode lens is applied to the eye as photoreceptor response to varying degrees of quick light pulses is measured. Patients exhibiting the retinitis pigmentosa phenotype would show decreased or delayed electrical response in the rod photoreceptors, as well as possibly compromised cone photoreceptor cell response. The patients family history is also considered when determining a diagnosis due to the genetic mode of inheritance of retinitis pigmentosa. At least 35 different genes or loci are known to cause "nonsyndromic RP" (RP that is not the result of another disease or part of a wider syndrome). Indications of the RP mutation type can be determine through DNA testing, which is available on a clinical basis for:

RLBP1 (autosomal recessive, Bothnia type RP)
RP1 (autosomal dominant, RP1)
RHO (autosomal dominant, RP4)
RDS (autosomal dominant, RP7)
PRPF8 (autosomal dominant, RP13)
PRPF3 (autosomal dominant, RP18)
CRB1 (autosomal recessive, RP12)
ABCA4 (autosomal recessive, RP19)
RPE65 (autosomal recessive, RP20)For all other genes (e.g. DHDDS), molecular genetic testing is available on a research basis only.