On- And Off-ERG Responses Driven By L- And M-cones

摘要

Purpose: : To study On- and Off-responses driven by L- and M-cones and by simultaneous modulation of the two in phase or in counterphase using sawtooth modulation profiles. Methods: : A four primary LED stimulator was used to create sawtooth stimuli that elicit L- or M-cone responses (each at 18 and at 8% cone contrast; triple silent substitution): rapid-on ramp-off (+L or +M) for On-responses; rapid-off ramp-on (-L or -M) for Off-responses. In addition, the two were modulated simultaneously with equal contrasts (silent substitution for rods and S-cones) either in-phase (+L+M for On-responses; -L-M for Off-responses; 42% and 21% cone contrast in each cone) or in counterphase (+L-M rapid L-on M-off; -L+M rapid L-off, M-on; 9% cone contrast in each). ERG responses to these stimuli were measured in four color normal subjects. Results: : The responses to L- and M-cone isolating stimuli were quite different: +M responses displayed much smaller and delayed A- and B-waves than +L responses, but similar PhNRs. -M responses were of similar amplitude but delayed compared to -L responses. ERGs to +L+M, -L-M displayed properties that were similar to the L-cone driven responses. +L-M and -L+M responses displayed properties of both the responses to L- and M-cone and isolating stimuli. Conclusions: : There are fundamental differences between L-and M-cone driven On- and Off-responses, suggesting different post-receptoral processing of the signals driven by the two cone types. Responses to in-phase and counterphase simultaneous modulation of L- and M-cones are also differently processed.