The historical development of the idea that light deprivation could have therapeutic benefit for patients with retinitis pigmentosa is reviewed. A patient with autosomal recessive and a patient with autosomal dominant retinitis pigmentosa participated in a trial of light deprivation of one eye with an opaque scleral contact lens for 5 yr for about 6–8 hr per day. Each showed comparable progression in both eyes as monitored by changes in visual acuity, visual fields, fundus appearance, and electroretinograms (ERGs).

In addition to the well known abnormality in dark adaptation with consequent night blindness, studies of cone ERG b-wave implicit times have shown that patients with early retinitis pigmentosa can have a defect in the mechanism by which their cone system adapts to light. Until more is known about this defect and the pathogenesis of retinitis pigmentosa, we recommend that patients wear dark sunglasses for outdoor use although we have no evidence at this time to substantiate that light deprivation with any type of sunglass or use of an opaque lens will modify the rates of progression of these diseases.