Abstract
Purpose :
The presence of eye movements during multifocal electroretinograms hinders the spatial resolution and location specificity that can be achieved. A solution to this problem could be a gaze-contingent display coupled with an ERG system. Here, we present the early development of such a system that could potentially improve the diagnostic value of ERG recordings.
Methods :
Eye movements were recorded using an Eyelink 1000 plus eye tracker with a 2KHz sampling rate (SR Research CA). Simultaneously, single channel ERG signals were recorded from one eye using a 1902 amplifier and a 1401 data acquisition system (CED UK) with 100K gain and frequency bandwidth 0.2 - 100Hz. Stimuli were generated using Psychtoolbox and MATLAB, and were presented onto a monitor with a refresh rate of 120Hz through the Bits# stimulus generator (CRS UK). We recorded electroretinograms (ERG) with and without gaze-contingency. The stimulus, a white 10 degree disk (330 cd/m2) on a neutral background (165 cd/m2), was on for one monitor frame, and for the gaze-contingent mode its location was updated based on an average gaze location sampled over 30 ms before the stimulus onset. The ERG acquisition system was time-locked with the stimulus presentation via a TTL trigger generated by the Bits#. The gaze-contingent system’s latency was measured with a modified method described before (Saunders & Woods 2013). Briefly, an Arduino Duo board that controlled an infrared LED generated artificial blinks and disrupted the eye tracking causing a luminance change on the monitor. With a high-speed camera (1000 fps) the frame difference between the onset of a blink and the onset of the monitor luminance change, i.e. the system latency, was estimated.
Results :
The latency of the gaze-contingent system based on 34 measurements was calculated to be 10.79 ± 2.9 ms. Qualitative comparison of the ERG responses recorded with a gaze-contingent and a fixed stimulus suggests that the recordings are similar, in terms of the ERG components, but also latency and amplitude.
Conclusions :
Using a video-based eye tracker and a data acquisition system we created a gaze-contingent ERG system. The use of our system in future studies using a multifocal stimulus could potentially improve the spatial resolution and location specificity that can be achieved without the need of spatial averaging.
This is a 2021 ARVO Annual Meeting abstract.