SECTION 26: RETINAL DYSTROPHIES
Retinitis Pigmentosa Shilpa Desai | A. Yasin Alibhai
Retinitis pigmentosa (RP) refers to a heterogeneous group of inherited disorders that are characterized by loss of retinal cell function, preferentially in the peripheral retina. RP can have varying severity, age of onset, mode of inheritance, and systemic associations. RP may be inherited in an autosomal dominant, autosomal recessive, or X-linked recessive fashion. The X-linked form of the disease is typically the most severe. The disease is often secondary to mutations in the rhodopsin gene, though some forms have been linked to mutations in the RDS gene (Anasagasti et al., 2012). Generally, RP is characterized by a slowly progressive loss of night vision (nyctalopia) along with contraction of the visual field. In later stages of the disease central acuity is affected, which may cause profound vision loss. Typical fundus abnormalities include waxy pallor of the optic nerve, a tapetal-like reflex resulting from changes in the retinal pigment epithelium (RPE), narrowing of the peripheral retinal vasculature, and bone-spicule changes in the mid-peripheral retina (Fig. 1). Definitive diagnosis requires electrophysiologic testing. Computed tomography is useful to aid in the initial diagnosis and detecting associated macular abnormalities such as cystoid macular edema (Fig. 2). Treatment of RP is limited at this time, although retinal prosthetic implants are available for extremely severe cases (Farrar et al., 2012).
• Symptoms include nyctalopia, constricted visual field, and in some cases profound vision loss.
• Waxy pallor of the optic nerve, attenuation of the retinal vessels,
and bone spicules in the peripheral retina are common clinical findings. OCT findings in early/milder disease include relative preservation of the central retina and RPE with loss of the outer retina and RPE adjacent to the fovea. OCT findings in advanced/severe disease include marked attenuation of all retinal layers, particularly the outer retina and photoreceptors. Associated cystoid macular edema may be identified on OCT.
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BIBLIOGRAPHY Anasagasti A, Irigoyen C, Barandika O, et al. Current mutation discovery approaches in retinitis pigmentosa. Vision Res. 2012;75:117–129. Farrar GJ, Millington-Ward S, Chadderton N, et al. Gene-based therapies for dominantly inherited retinopathies. Gene Ther. 2012;19(2):137–144. Wolfensberger TJ. The role of carbonic anhydrase inhibitors in the management of macular edema. Doc Ophthalmol. 1999;97(3-4):387–397.
FIG. 1. Color fundus photograph of a patient with typical RP. There is peripheral bone spicule deposition encroaching into the macula, optic nerve pallor, and prominent vascular attenuation. The central retina and RPE are preserved (“central island”).
FIG. 2. OCT B-scan corresponding to Fig. 1. There is significant thinning of the outer retinal layers and dropout of the RPE involving the edges of the macula. However, the central fovea is spared with normal retinal architecture.