Dependence of cone b-wave implicit time on rod amplitude in retinitis pigmentosa.
Computer-averaged full-field rod and cone electroretinograms (ERGs) were evaluated in 63 patients with retinitis pigmentosa and 116 normal subjects. Cone b-wave implicit times to 30 Hz white flicker and to 1.0 Hz white flashes on a white background were both inversely proportional to the log amplitude of the dark-adapted rod b-wave, even when controlling for the log amplitude of the dark-adapted cone b-wave. Cone ERGs were also obtained from a subset of 12 patients with retinitis pigmentosa in the presence of photopically-matched red and blue backgrounds that allowed direct assessment of the effect of rod function on cone b-wave implicit time in the patients. The effectiveness of the blue background in reducing cone b-wave implicit time relative to that obtained with the red background varied with the amplitude of the rod ERG. The results of both experiments suggest that delays in cone b-wave implicit time obtained with 30 Hz white flicker or with background adaptation in patients with retinitis pigmentosa are due, at least in part, to rod disease.
Birch
D G
DG
Retina Foundation of the Southwest, Presbyterian Medical Center, Dallas, TX 75231.
Sandberg
M A
MA
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003118:Color Perception / Q000502:physiology; D003623:Dark Adaptation; D004596:Electroretinography; D006801:Humans; D008875:Middle Aged; D008905:Minicomputers; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000503:physiopathology*; D012174:Retinitis Pigmentosa / Q000503:physiopathology*; D013997:Time Factors