On-response deficit in the electroretinogram of the cone system in X-linked retinoschisis.
OBJECTIVE
The purpose of this study was to evaluate the hypothesis that the reduced b-wave to a-wave ratio of the brief-flash electroretinogram (ERG) of the cone system typically observed in X-linked retinoschisis (XLRS) represents a relatively greater deficit in the ON response (response to light onset) than the OFF response (response to light offset). A second purpose was to investigate the use of sawtooth flicker as a stimulus for eliciting ERG ON and OFF responses.


METHODS
Light-adapted, full-field ERGs were recorded in six patients with XLRS and six age-similar control subjects in response to 8-Hz rapid-on and rapid-off sawtooth flicker to emphasize ON and OFF responses, respectively. ERG responses were analyzed in terms of the amplitudes and implicit times of the a-wave, b-wave, and d-wave components.


RESULTS
There was no significant difference between the patients with XLRS and the control subjects for either the amplitude of the a-wave of the ON response or the amplitude of the d-wave of the OFF response. However, the amplitude of the b-wave of the ON response was reduced significantly in the patients with XLRS, resulting in a significantly reduced b-wave to d-wave ratio. The patients' implicit times were increased significantly for all waveform components.


CONCLUSIONS
The reduced b-wave to d-wave ratio of the ERG of the cone system in these patients with XLRS is consistent with a relative dysfunction of the cone ON bipolar cell pathway in this disorder. The results show further that sawtooth flicker is a promising stimulus for eliciting well-defined ERG waveforms that can provide a quantitative assessment of the properties of ON and OFF responses in retinal disease.
Alexander
K R
KR
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, USA.
Fishman
G A
GA
Barnes
C S
CS
Grover
S
S
D000221:Adaptation, Ocular; D000293:Adolescent; D000328:Adult; D004596:Electroretinography; D008040:Genetic Linkage; D006801:Humans; D007395:Interneurons / Q000502:physiology; D008297:Male; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014792:Visual Acuity; D014960:X Chromosome