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Oguchi disease

Kalpana S, Muthayya M, Doctor PP

Department of A 9-year-old healthy boy was brought by his mother for non-progressive defective vision in the , Sri evenings in both eyes of four years duration. His day-time vision was normal. He did not give Ramachandra Medical history of trauma, previous ocular or systemic disease. His father has similar history of defective College and Research night vision. He was born of second-degree consanguinity and other two siblings were normal. In Institute, (A Harvard both eyes, uncorrected visual acuity was 6/6, N6. Slit lamp examination of anterior segment was Medical International normal. Color vision & field of vision (Octopus static white on white perimetry) were normal in affiliated institution), both eyes. examination of both eyes revealed a patchy grayish metallic phosphorescent Chennai - 600 089, India sheen. , macula, retinal vessels were normal. When the boy was subjected to dark Correspondence: for 3 hours, the fundus background colour changed from gray to red. (Mizuo Nakamura Priyanka Doctor, phenomenon) [Figures 1-4]. E-mail: [email protected] The ERG response, schematically illustrated in Figure 5, consists of an initial negative wave, the a­ wave, followed by a second positive wave, the b-wave. The a-wave is derived from the retinal Received : 10-06-05 photoreceptors: the rods and cones. It was originally thought that the Müller cells produced the b- Review completed : 23-07-05 wave, but more recent findings suggest that the b-wave is actually a result of bipolar cell activity. Accepted : 17-08-05 Since the nucleus of the Müller cell resides within the bipolar cell layer, this response is therefore PubMed ID : indicative of changes occurring in that particular layer. There is no contribution to the ERG from J Postgrad Med 2006;52:143-4 the retinal ganglion cells. ERG of our patient showed a rod/ max combined/ Oscillatory Potentials

(OPs) response, in which the b wave amplitude was diminished disappearance of the unusual discoloration of the normal in both eyes [Figure 6]. The Cone ERG was normal in both reddish appearance, called Mizuo-Nakamura phenomenon.[1] eyes [Figure 7]. Oguchi’s disease is also unique in the electroretinographic responses in the light- and dark-adapted condition. B wave Examination of the patient’s mother & other two siblings were amplitude is reduced in rod response and cone response is unremarkable. His father could not be examined as he was a normal.[2] Recent identification of the gene convict under custody. mutation[3,4] in chromosome 2q[5] in patients with Oguchi’s disease may account for the characteristic fundus and Discussion functional abnormality. As rhodopsin works with arrestin in shutting off rhodopsin after it has been activated Oguchi’s disease, first described by Chuta Oguchi in 1907, is by a photon of light, it has been proposed that some cases of a rare autosomal recessive disorder characterized by Oguchi disease are due to defects in .[6] congenital stationary night blindness and a unique morphological and functional abnormality of the . In our patient, the classical Mizuo phenomenon was present Patients have non-progressive night blindness since young and the fundus discolouration returned to normal with dark childhood with normal day vision, but often report adaptation. The differential diagnosis includes Stargardts improvement of light sensitivities when they remain long in disease, female carrier of pigmentosa, juvenile the dark environment; dark-adaptation study demonstrates , progressive . All these conditions that highly elevated rod thresholds decrease several hours later may have fundus changes but without the classical Mizuo and eventually result in a recovery to the normal or nearly phenomenon. In ERG both rod and cone abnormalities are normal level. The fundus has a diffuse or patchy appearance, found. silver-gray or golden-yellow metallic sheen and the retinal vessels stand out in relief against the radiant background. A This rare disease is more commonly encountered in Japan and prolonged dark adaptation of three hours or more, leads to is presented in view of its novelty.

J Postgrad Med April 2006 Vol 52 Issue 2 143 � � Kalpana, et al.: Oguchi disease

Figure 5: Schematic diagram of the basic ERG responses defined by standard. Figure 1: Fundus picture of right eye showing light adapted retina with gray discoloration of retina.

Figure 2: Fundus picture of right eye after dark adaptation showing normal Figure 6: ERG:Rod/max combined/OPs response red background

Figure 3: Fundus picture of left eye showing light adapted retina with gray discolouration of retina. Figure 7: ERG:Single Flash cone/30 Hz

References

1. Usui T, Ichibe M, Ueki S, Takagi M, Hasegawa S, Abe H, et al. Mizuo phenomenon observed by scanning laser ophthalmoscopy in a patient with Oguchi disease. Am J Ophthalmol 2000;130:359-61. 2. Yamamoto S, Hayashi M, Takeuchi S, Shirao Y, Kita K, Kawasaki K. Normal S cone electroretinogram b-wave in Oguchi’s disease. Br J Ophthalmol 1997;81:1043-5. 3. Palczewski K, Rispoli G, Detwiler PB. The influence of arrestin (48K protein) and rhodopsin kinase on visual transduction. Neuron 1992;8:117-26. 4. Maw M, Kumaramanickavel G, Kar B, John S, Bridges R, Denton M. Two Indian siblings with Oguchi disease are homozygous for an arrestin mutation encoding premature termination. Hum Mutat 1998;1:S317-9. 5. Maw MA, John S, Jablonka S, Muller B, Kumaramanickavel G, Oehlmann R, et al. Oguchi disease: suggestion of linkage to markers on chromosome 2q. J Med Genet 1995;32:396-8. Figure 4: Fundus picture of left eye after dark adaptation showing normal 6. Yamamoto S, Sippel KC, Berson EL, Dryja TP. Defects in the rhodopsin kinase red background gene in the Oguchi form of stationary night blindness. Nat Genet 1997;15:175­ 8.

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