Retinitis pigmentosa (RP) encompasses a heterogeneous group of inherited disorders that result in loss of retinal cell function (starting with photoreceptors) preferentially in the peripheral retina. Eventually, the macula can be involved in late stages. The prevalence is approximately 1 in 5000. RP can be categorized several different ways: cone–rod versus rod–cone dystrophies, via the inheritence patterns, or by the actual genetic defect, if it is known.
Nyctalopia is a hallmark feature of the disease. Peripheral vision is impaired early, especially in rod–cone dystrophies, and is slowly progressive. Central vision can also be lost, but typically occurs later in the disease course, although central vision can be impaired at any point by cystoid macular edema. Examination findings include characteristic bone spicule intraretinal deposits, vascular attenuation, and optic nerve pallor (Fig. 16.1.1).