Abstract
Purpose :
Despite the critical role of lateral interactions in retinal processing, there is no validated electroretinogram (ERG) to specifically probe this function. Using a novel ERG paradigm, we investigated the effect of background contrast on center-surround retinal response mechanisms elicited by a series of pattern-reversing stimuli.
Methods :
Seven subjects (age 27 +/- 2, range 25-32 years) underwent a thorough vision screening. All subjects had BCVA 20/20 or better and no ocular pathology or vision deficit other than refractive error. The ERG stimuli were presented on a 48” LG OLED monitor with a 120 Hz refresh rate. A ring of 8 circular dead leaves stimuli (4 deg diameter each) was presented at each of two mid-peripheral eccentricities: 6 or 10 deg. The dead leaves pattern contrast reversed at a rate of 7.5 reversals/s (15 Hz) and an average contrast of 50%. The background pattern of isotropic noise (see figure) contrast-reversed at 1 reversal/s (2 Hz). ERGs were obtained with background contrast of 0%, 25%, 50%, and 75%. The average luminance of the stimuli and background were held constant for all experimental conditions (75 cd/m2). ERGs were recorded monocularly with a DTL electrode and an undilated pupil. Skin electrodes were used for ground and reference. Fast Fourier transform was performed to isolate the 15 Hz harmonic corresponding to retinal responses elicited by the dead leaves patterns. Background contrast response curves were generated for each eccentricity.
Results :
At 6-deg eccentricity, the amplitude of the 15 Hz harmonic increases in a monotonic/linear relationship with background contrast (R^2 =0.8825). ERG responses doubled from baseline (0%) to 75% background contrast condition (ratio: 2). The results from the 10-deg condition showed a biphasic change as a function of background contrast. Although retinal responses increased from baseline to 75% background contrast (ratio of 1.3) responses decreased from baseline to 25% (ratio: 0.5) and 50% (ratio: 0.88) background contrast, indicating an inhibitory relationship.
Conclusions :
These findings suggest center-surround interactions in retinal processing independent of changes in mean luminance as well as a possible method for evaluating lateral interactions using ERG. Such methodology would be useful for analysis of functional deficits in the retina that may not be readily apparent on a structural level.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.