Human photopic ON- and OFF-ERG responses elicited by square wave and sawtooth stimuli

ABSTRACT

In this study, the on- and off-responses elicited by luminance square wave and sawtooth stimuli at different temporal frequencies and contrasts are described quantitatively. Adding on- and off-responses reveals response asymmetries. Full-field stimuli were produced using a Ganzfeld bowl with arrays of light-emitting diodes (LEDs) as light sources. ERG responses were recorded from six normal subjects. The amplitudes and implicit times of components of the on- and off-responses and the additions were analyzed. The amplitudes of the on-, off- and addition components elicited by square wave stimuli did not depend on temporal frequency with the exception of the late negative components, which decreased with increasing temporal frequency up to 4 Hz. The amplitudes of all components elicited by sawtooth stimuli, except the P-on, decreased with increasing temporal frequency. The amplitude of all components elicited by square wave and sawtooth stimuli were positively correlated with stimulus contrast. The implicit times of the on-components to square wave stimuli and all response components to sawtooth stimuli decreased with increasing temporal frequency. Contrast had an effect on the implicit times of the N-on, P-on, P-off and P-add components elicited by square wave stimuli and the N-on, P-on, P-add and LN-on components elicited by sawtooth stimuli. The asymmetries between on- and off-responses can possibly be used to reveal inner retinal contributions and may therefore be interesting in detecting glaucomatous changes.(AU)