Shortening of the rod outer segment in Oguchi disease

Abstract

Dear Editor, Oguchi disease, characterized by stationary night blindness, is an inherited and non-progressive retinal disorder that affects the rods and causes impaired night vision [1]. Histologic findings have not been reported. We observed microstructural change of the retina in Oguchi disease using spectral domain optical coherence tomography (SD-OCT). A 31-year-old man had night blindness since childhood. His best-corrected visual acuity was 1.2 bilaterally. On ophthalmoscopic examination (Fig. 1), his fundus had a golden sheen reflex, except for the macular and perimacular areas. The macula had a normal red reflex, but the perimacular area was grayish bilaterally. A full-field ERG showed normal cone and flicker responses; the rod response was non-recordable. Multifocal ERG showed a normal response. The visual field was within normal limits on Goldmann perimetry. He was diagnosed with Oguchi disease. Oguchi disease has five subtypes depending on the location of the golden sheen reflex, i.e., the entire fundus, macula sparing, posterior fundus sparing, peripheral sparing, and far periphery sparing. The current case corresponds to the posterior fundus-sparing type. In a horizontal 6-mm scan across the fovea, the junction between photoreceptor inner and outer segment (IS/OS ) appeared normal in the macula within a 3-mm diameter; however, the distance between the IS/OS and retinal pigment epithelium (RPE) suddenly decreased, and the IS/ OS line was not identifiable in a 3-mm-wide perimacular ring, where the retina was attenuated because of decreased thickness of the outer nuclear layer (ONL). The IS/OS line emerged outside of the perimacular ring in the midperiphery, but the distance between the IS/OS and RPE was short, such that the two reflective lines fused into one broad reflective band in some areas. The midperipheral retinal thickness was normal. SD-OCT (Fig. 2) showed that the distance between the IS/OS line and RPE was short in the midperipheral fundus, which had a golden sheen. However, the IS/OS line appeared normal in the macula, where the fundus color was normal. The IS/OS line was not identifiable in the perimacular area, where the fundus was grayish, resembling an early change in retinitis pigmentosa. Since the IS/OS line indicates high reflectivity at the proximal portion of the photoreceptor outer segment, the decreased distance between the IS/OS and the RPE suggests shortening of the outer segment. OCT suggested that the lesion responsible for the golden sheen reflex appeared to be shortening of the rod outer segment. Full-field ERG showed a normal cone response and a non-recordable rod response. Since the cones were intact, the IS/OS appeared normal in the macula where the cones aggregate, and the fundus reflex was normal. It was noteworthy that the fundus reflex was grayish in the perimacular area where the IS/OS was not identifiable with attenuation of the ONL. The loss of the Graefes Arch Clin Exp Ophthalmol (2009) 247:1561–1563 DOI 10.1007/s00417-009-1114-6