Abstract
Purpose :
To study the effect of sinusoidally modulating background on the photopic flash ERGs.
Methods :
Four healthy subjects (age: 28-62 years; one female) participated in the study. We measured the response to flashes (500 cd/m2, 1ms long) on a steady background (50 cd/m2) as a control and a sinusoidally modulating (50 cd/m2 mean luminance) background of 1, 5, 10, and 25Hz temporal frequencies. The flashes were presented at 0° (mean luminance), 90° (100 cd/m2 instantaneous luminance) and 270° (0 cd/m2 instantaneous luminance) during the carrier sine wave. The responses to the carriers (sine wave only) were also recorded as control measurements and subtracted from the responses to flash plus sine carriers to obtain the flash ERGs at different phases.
Results :
The responses to flashes were strongly altered when presented at different phases on the sine wave and particularly at low frequencies. The response was larger for the flash at 270° phase compared to the control flash ERG (flash on steady background) and the flash at 0° and 90° phases. The response to the flash at 90° was smaller than the other responses. The response to the flash at 0° were comparable to the flash ERG on a steady background. The effects of background modulation on the flash ERG decreased with increasing frequency of the background. The amplitudes of the components could be described by the Weber fraction plus saturation and a delay.
Conclusions :
The proposed technique can be useful to enhance the flash ERG responses and to increase signal to noise ratio. Weber fraction of the flashes is an adequate quantification of stimulus strength to describe the amplitudes of the flash ERGs.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.