2.12 Oguchi’s Disease 119
Oguchi’s disease, first reported by Oguchi in 1907 [1], is an unusual form of congenital stationary night blindness. It is characterized by a peculiar grayish white discoloration of the fundus (Fig. 2.89). In 1913 Mizuo found that this unusual fundus coloration disappeared after a long period of dark adaptation [2]. This change in fundus coloration is now called the Mizuo phenomenon (Fig. 2.89).
Mutations in the arrestin gene [3] or the rhodopsin kinase gene [4] cause the recessive form of Oguchi’s disease.Arrestin and rhodopsin kinase act in sequence on reactive rhodopsin to stop the phototransduction cascade. Most patients who have been reported with muta- tions in the arrestin gene are Japanese [5].
Visual acuity, visual field, and color vision are normal in patients with Oguchi’s disease.
Rod function is absent both subjectively and electroretinographically after 30 min of dark adaptation, but the subjective rod function may reappear after 2–3 h of dark adaptation [6]
(Fig. 2.83).
Full-field ERGs recorded after 30 min of dark adaptation from seven patients with Oguchi’s disease [7] are shown in Fig. 2.90. The rod ERGs are absent, and the cone-mediated ERGs are essentially normal. The mixed rod–cone ERG (Fig. 2.91) has a negative
configuration with relatively well-preserved OPs. For comparison, the mixed rod–cone ERG of a patient with complete CSNB is also shown.
The a-wave amplitude in Oguichi patients is reduced compared to that of normal controls and patients with complete CSNB. After 3 h of dark adaptation, the amplitudes of the a-wave and b-wave of the mixed rod–cone ERGs are larger, but they are still not normal.
Consistent findings in the mixed rod–cone ERGs recorded after 30 min of dark adaptation in patients with Oguchi’s disease are (1) nega- tive ERGs with reduced a-waves; (2) nearly absent b-waves; (3) relatively well-preserved OPs; and (4) essentially normal cone-mediated ERGs (Fig. 2.91).
The pathogenic defect in the cone visual pathway in Oguchi’s disease is different from that of complete CSNB and incomplete CSNB.
Unlike complete and incomplete CSNB, the amplitude and waveform of the photopic ERGs elicited by long-duration stimuli are normal, indicating that the on and off systems of the cone visual pathway are functioning normally (Fig. 2.92). The focal macular ERGs are also normal (Fig. 2.93). The EOG ratio in Oguchi’s disease is lower than normal in most Japanese patients [7].
2.12 Oguchi’s Disease
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120 2 Hereditary Retinal and Allied Diseases
Fig. 2.89. Fundus of a patient with Oguchi’s disease while light- adapted (top) and after a long period of dark-adaptation (bottom), demonstrating the Mizuo phenomenon
Fig. 2.90. Full-field ERGs recorded from a normal control and seven patients with Oguchi’s disease. (From Miyake et al. [7], with permission) RDI2(104%) 9/9/05 7:53 PM Page 120
2.12 Oguchi’s Disease 121
Fig. 2.91. Full-field mixed rod–cone ERGs recorded from a normal control, a patient with complete CSNB, and seven patients with Oguchi’s disease.
ERGs were recorded after 30 min (middle) and after 3 h (right) of dark adaptation. (From Miyake et al. [7], with permission)
Fig. 2.92. Full-field photopic ERGs elicited by long-duration stimuli and recorded from a normal subject, a patient with Oguchi’s disease, and a patient with complete CSNB. (From Miyake et al. [7])
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with the Oguchi form of stationary night blindness.
Nat Genet 15:175–178
5. Nakamura M, Yamamoto S, Okada M, Ito S, Tano Y, Miyake Y (2004) Novel mutations in the arrestin gene and associated clinical features in Japanese patients with Oguchi’s disease. Ophthalmology 111:1410–1414
6. Carr RE, Gouras P (1965) Oguchi’s disease. Arch Ophthalmol 73:646–656
7. Miyake Y, Horiguchi M, Suzuki S, Kondo M, Tanikawa A (1996) Electrophysiological findings in patients with Oguchi’s disease. Jpn J Ophthalmol 40:511–519
Fig. 2.93. Focal macular ERGs elicited by three differently sized spots from a patient with Oguchi’s disease and recorded with two different time constants (T.C.). All components are within the normal range, indicating that the macula was functioning normally
References
1. Oguchi C (1907) Uber eine Abart von Hemeralopie.
Acta Soc Ophthalmol Jpn 11:123–134
2. Mizuo G (1913) On a new discovery in the dark adaptation of Oguchi’s disease. Acta Soc Ophthal- mol Jpn 17:1854–1859
3. Fuchs S, Nakazawa M, Maw M, Tamai M, Oguchi Y, Gal A (1995) A homozygous 1-base pair deletion in the arrestin gene is a frequent cause of Oguchi disease in Japanese. Nat Genet 10:360–362
4. Yamamoto S, Sippel KC, Berson EL, Dryja TP (1997) Defects in the rhodopsin kinase gene in patients RDI2(104%) 9/9/05 7:53 PM Page 122
