Disorders of the Fundus Edited by Ronald E. Cim, MD
9. Retinitis Pigmentosa RONALD E. CARR, MD, KENNETH G. NOBLE, MD
The name "retinitis pigmentosa" was originally coined by Donders, and, while etymologically incorrect, it does convey a rather specific retinal picture to the ophthalmologist. However, the name can also be used as a prototype for the very wide variety ()f generalized heredoretinal degenerations. The disease in its classic form usually is accompanied by the subjective complaint of poor night vision and gradually worsening peripheral vision but with retention of good central vision early in the course. Psychophysically, the complaint of poor night vision is correlated with the elevated dark adaptation curve (Fig IA) and the poor peripheral vision by a ring scotoma which, as the disease progresses, will gradually break out into the far periphery and move toward fixation, leaving only a small central island (tunnel vision) (Fig IC). The primary diagnostic test is the electroretinogram, which will show an absent or markedly reduced response in virtually all cases at any stage of the disease (Fig IB). In those rare cases in which a larger response may lead to some question of diagnosis, the increased latency of the response in retinitis pigmentosa may serve to distinguish this disorder from other diseases. The fundus picture in the classic case of retinitis pigmentosa will show diffusely narrowed arterioles, bone spicule pigmentary clumping in the mid periphery , and a waxy pallor to the optic disc (Fig 2). Since the pigmentary abnormalities may vary considerably, from no changes (sine pigmento), to mild mottling ("salt and pepper"), to heavy irregular pigment accumulations, the diagnosis of a generalized tapetoretinal degeneration is confirmed by the visual function tests. In more than 50% of patients, vision will be compromised owing to macular pathology, such as atrophy of the retinal pigment epithelium and/or choriocapillaris, cystoid macular edema-with or without leakage of the perifoveal capillaries-(Fig 3), macular cysts or holes, or preretinal membranes. Retinitis pigmentosa is associated with other ocular findings including an exudative response resembling Coats' syndrome, drusen of the optic nerve, and early formation of posterior subcapsular cataracts (Fig 4). In
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From the Department of Ophthalmology, New York University Medical Center, New York. Reprint requests to Ronald E. Carr, MD, Department of Ophthalmology, New York University Medical Center, 550 First Avenue , New York, NY 10016.
0161-6420/8110200/0169/$00.70 © American Academy of Ophthalmology
af feet ed ----------• Figs lA-C. A, visual function testing in retinitis pigmentosa dark adaptation. The normal individual (hatched line) has a bipartite curve with the initial portion representing cone adaptation and the second portion representing rod adaptation. The cone-rod break occurs at 5 to 7 minutes and the final (absolute) rod threshold is reached at 25 to 30 minutes. The patient with retinitis pigmentosa (solid line) has an elevated cone and rod threshold. B, visual fields. The midperipheral rods are affected earliest, which accounts for the characteristic ring scotoma. C, electroretinography. The electroretinogram is invariably abnormal with the scotopic response affected earlier and more severely than the photopic response.
Figs 2A and B. Top left and right, typical retinitis pigmentosa: the typical fundus picture in retinitis pigmentosa has diffusely attenuated arterioles, an abnormal tapetal reflex, bone spicule pigment accumulation, and a waxy pallor of the optic disk. Figs 3A-C. Cystoid macular edema: This patient had typical bone spicule pigmentation in the mid periphery and diminished central vision. A, center left, the macula had a cystic appearance in each eye. B, center right, the fluorescein angiogram showed the typical appearance of cystoid macular edema with dilation and leakage of the perifoveal capillaries and C, bottom, an accumulation of dye in the cystic spaces in the late stage ("flower petal" pattern).
Figs 4A-C. Associated ocular findings in retinitis pigmentosa include A, top left, an exudative response, B, top right, posterior subcapsular cataracts, and C, center, drusen ofthe optic nerve head. Figs SA-B. Female carrier sign: A, bottom left, the characteristic fundus picture of a female carrier is a scintillating golden reflex in the posterior pole. B, bottom right, fluorescein angiography fails to show any abnormality.
OPHTHALMOLOGY • FEBRUARY 1981
addition, a wide variety of systemic disorders are seen with a generalized retinal degeneration including the Bassen-Kornzweig syndrome (abetalipoproteinemia), Refsum's disease, some of the mucopolysaccharoidoses, Laurence-Moon and Bardet-Biedl syndrome, hereditary ataxias (Friedrich's, Marie's) and external ophthalmoplegia (with or without cardiac abnormalities). The heredity of this disease is in any of the three classic modes: autosomal recessive, autosomal dominant (AD), or X-linked recessive (XLR). The AD vari-
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ety usually has the best prognosis for retention of vision with the XLR variant the most severe. An important problem in genetic counseling is the accurate classification of the simplex male. Characteristic retinal changes in the X-linked carrier female may aid in differentiating this genetic variant. A certain number of female carriers have a scintillating golden reflex around the macular area and/or some peripheral pigment changes (Fig 5). Likewise, mild electroretinographic changes under certain test conditions have recently been described in the female carrier.