Retinitis Pigmentosa and Other Dystrophies

Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal degenerations characterized by progressive degeneration of rod and cone cells that affects predominantly peripheral visual fields. Macular edema may cause additional central visual acuity decrease. Cystoid macular edema (CME) is one of the few treatable causes of visual loss in RP. The prevalence of CME in RP has been found to be between 10 and 20% on fluorescein angiography-based studies, and as high as 49% on reports based on optical coherence tomography. Macular edema can manifest at any stage of the disease and may be unilateral or bilateral. It can be found in any genetic form, but is more often associated with RP caused by CRB1 mutations. The origin of macular edema in RP patients still remains poorly understood. Some mechanisms have been suggested, including antiretinal antibodies (retinal, carbonic anhydrase, and enolase antibodies), vitreous traction, retinal pigment epithelium dysfunction, and Müller cell edema. There is no gold standard therapeutic strategy. Drug therapy is the primary treatment. Systemic carbonic anhydrase inhibitors, such as oral acetazolamide or topical dorzolamide, are still the mainstays of initial therapy. If CME is refractory to acetazolamide, intravitreal corticosteroid injections may be a therapeutic option. However, antivascular endothelium growth factor injections have limited effect and should be avoided. Vitrectomy has also been evaluated, but its exact role remains to be determined. The benefits of these therapies are variable among patients. The establishment of therapeutic approaches is limited by our poor understanding of the pathophysiology of CME in patients with RP. Autoimmune retinopathies (AIRs) are a group of rare diseases characterized by acute or subacute progressive vision loss and are thought to be mediated by autoantibodies specific to retinal antigens. The AIRs encompass paraneoplastic syndromes, such as cancer-associated retinopathy and melanoma-associated retinopathy, and a larger group of AIRs that have similar clinical and immunological findings but without underlying malignancy. These diseases may also be complicated by macular edema. RP is one of the most common forms of inherited retinal degeneration. It displays extensive clinical and genetic variations and leads to progressive blindness with variable onset.