SWS (blue) cone hypersensitivity in a newly identified retinal degeneration.
Photoreceptor-mediated mechanisms were studied in patients with a recently identified retinopathy typified by night blindness, cystoid maculopathy, and similar scotopic and photopic electroretinograms (ERGs). Dark-adapted spectral sensitivity functions were only partly explained as composites of rod and cone curves shifted to lower sensitivities; there was unusually high sensitivity from 400-460 nm. A rod mechanism, reduced in sensitivity by at least 3 log units, was detectable with dark adaptometry. No measurable rhodopsin was found with fundus reflectometry. Light-adapted spectral sensitivities were subnormal for wavelengths greater than 500 nm but supernormal from 420-460 nm. On a yellow adapting field, the supernormal spectrum approximated that of the short-wavelength-sensitive (SWS) cone system. With spectral ERGs, two mechanisms were demonstrated. Dark- and light-adapted ERGs to green, orange-yellow, and red stimuli had similar waveforms and coincident intensity-response functions on a photopic intensity axis. ERGs to blue and blue-green stimuli were similar, and intensity-response functions coincided on a SWS cone intensity axis. Patients varied in the degree to which rod and midspectral cone function were decreased and SWS cone function was increased.
Jacobson
S G
SG
Department of Ophthalmology, University of Miami School of Medicine, Bascom Palmer Eye Institute, Florida 33101.
Marmor
M F
MF
Kemp
C M
CM
Knighton
R W
RW
D000293:Adolescent; D000328:Adult; D002648:Child; D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D008268:Macular Degeneration / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009755:Night Blindness / Q000209:etiology; D010786:Photoreceptor Cells / Q000503:physiopathology*; D011601:Psychophysics; D012162:Retinal Degeneration / Q000150:complications / Q000503:physiopathology*; D012243:Rhodopsin / Q000378:metabolism; D012684:Sensory Thresholds; D014792:Visual Acuity; D058609:Visual Field Tests
D012243:Rhodopsin