Two siblings with late-onset cone–rod dystrophy and no visible macular degeneration
Case 2 was the younger sister of case 1. She was 80 years old and had first noticed a decrease in her vision and photophobia in both eyes in her early seventies. Her cataract was removed in both eyes at age 76; however, her vision was not improved.\nOur examination showed that her decimal BCVA was 0.4 OD with +0.25 D and 0.2 OS with +0.5 D. Her pupillary light reflexes and intraocular pressures were normal in both eyes. There was no history of retinotoxic drug use.\nHer fundus was normal except for a slight mottling of the retinal pigment epithelium in the midperiphery. No macular degeneration was seen in either eye (). FA was not performed because of her allergy to fluorescein sodium. Goldmann kinetic perimetry revealed a central scotoma in the left eye and a mild constriction of the visual fields in both eyes (). Farnsworth D-15 test showed tritan axis errors in both eyes. Goldmann–Weekers dark adaptometry showed a slight elevation of the light threshold in both eyes (). The full-field scotopic ERGs elicited by low-intensity stimuli were slightly reduced, and the scotopic high-intensity ERGs were normal, except the oscillatory potentials were reduced. The photopic single-flash and 30 Hz flicker ERGs were nonrecordable in both eyes (). The mfERGs were nonrecordable in the right eye and reduced in the central and midperipheral areas of the left eye (). OCT showed similar findings to her elder brother in the macular area (). The photoreceptor inner segment/outer segment junction line was indistinct. The thickness of the outer nuclear layer was 130 μm OD and 129 μm OS (normal mean 172 ± 17 μm) at the fovea, 43 μm OD and 65 μm OS (normal mean 128 ± 19 μm) at 0.5 mm superior to the fovea, and 32 μm OD and 22 μm OS (normal mean 135 ± 23 μm) at 0.5 mm inferior to the fovea. At 2 mm superior to the fovea, the thickness of the outer nuclear layer was 65 μm OD and 76 μm OS (normal mean 97 ± 13 μm), and at 2 mm inferior to the fovea it was 65 μm OD and 43 μm OS (normal mean 88 ± 18 μm). Thus, the outer nuclear layer was thin, especially in the parafoveal region of both eyes ().