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. Vision decreases as the macula becomes increasingly involved and can evolve to legal blindness.
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 orally once a day may help slow disease progression in some patients. Patients taking vitamin A palmitate should have regular liver 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.
For patients with cystoid macular edema, carbonic anhydrase inhibitors given orally (eg, acetazolamide) or topically (eg, dorzolamide) may yield mild vision improvement. Voretigene neparvovec-rzyl has recently become available for the treatment of confirmed biallelic RPE65 mutation-associated retinal dystrophy. This is an adenovirus vector-based gene therapy that is injected surgically into the subretinal space in patients who have viable retinal cells and this specific mutation (1). This treatment can restore ambulatory vision in these patients. For patients with total or near total vision loss, epiretinal and subretinal computer chip implants can restore some visual sensations.
Maguire AM, Russell S, Wellman JA, et al: Efficacy, safety, and durability of voretigene neparvovec-rzyl in RPE65 mutation-associated inherited retinal dystrophy: Results of phase 1 and 3 trials. Ophthalmology 126(9):1273-1285, 2019. doi: 10.1016/j.ophtha.2019.06.017.
Early symptoms of retinitis pigmentosa include defective night vision and peripheral vision.
Diagnose by hyperpigmentation in a bone-spicule configuration on funduscopy and confirm with electroretinography.
Prescribe vitamin A, omega 3 fatty acids, and lutein and zeaxanthin supplements to decrease rate of vision loss.
Treat patients with cystoid macular edema with carbonic anhydrase inhibitors.
Gene therapy with voretigene neparvovec-rzyl can restore ambulatory vision in patients with confirmed biallelic RPE65 mutation-associated retinal dystrophy.