Retinitis pigmentosa is a slowly progressive, bilateral degeneration of the retina and retinal pigment epithelium caused by various genetic mutations. Symptoms include night blindness and loss of peripheral vision. Diagnosis is by funduscopy, which shows pigmentation in a bone-spicule configuration in the equatorial retina, narrowing of the retinal arterioles, a waxy pallor of the optic disk, posterior subcapsular cataracts, and cells in the vitreous. Electroretinography helps confirm the diagnosis. Vitamin A palmitate, omega-3 fatty acids, and lutein plus zeaxanthin may help slow progression of vision loss.
Abnormal gene coding for retinal proteins appears to be the cause of retinitis pigmentosa; several genes have been identified. Transmission may be autosomal recessive, autosomal dominant, or, infrequently, X-linked. It may occur as part of a syndrome (eg, Bassen-Kornzweig, Laurence-Moon). One of these syndromes includes congenital hearing loss as well (Usher syndrome).
Retinal rods are affected, causing defective night vision that becomes symptomatic at varying ages, sometimes in early childhood. Night vision may eventually be lost. A peripheral ring scotoma (detectable by visual field testing) widens gradually, and central vision may also be affected in advanced cases.
Hyperpigmentation in a bone-spicule configuration in the midperipheral retina is the most conspicuous funduscopic finding. Other findings include the following:
The diagnosis is suspected in patients with poor night vision or a family history. Diagnosis is by funduscopy, usually supplemented with electroretinography. Other retinopathies that can simulate retinitis pigmentosa should be excluded; they include retinopathies associated with syphilis, rubella, phenothiazine or chloroquine toxicity, and nonocular cancer.
Family members should be examined and tested as necessary or desired to establish the hereditary pattern. Patients with a hereditary syndrome may wish to seek genetic counseling before having children.
There is no way to reverse damage caused by retinitis pigmentosa, but vitamin A palmitate 15,000 IU po once/day may help slow disease progression in some patients. Patients taking vitamin A palmitate should have regular liver function tests. Dietary supplementation with an omega-3 fatty acid (eg, docosahexaenoic acid) and an oral preparation of lutein plus zeaxanthin may also slow the rate of vision loss. Vision decreases as the macula becomes increasingly involved and can evolve to legal blindness. For patients with cystoid macular edema, carbonic anhydrase inhibitors given orally (eg, acetazolamide) or topically (eg, dorzolamide) may yield mild vision improvement. For patients with total or near total vision loss, epiretinal and subretinal computer chip implants can restore some visual sensations.