Abstract
Purpose :
Conventionally, PERG responses are obtained from a single stimulus field presented to the central retina (~15°). The PERG response provides information about Retinal Ganglion Cells (RGC) health, however, the spatial distribution of RGCs in the central retina is highly non-uniform. Using a custom build dual region pattern reversal display, we obtained PERG responses from 8 different 7.5 degree segments from the central 60° of the retina. We then used the previously described bideconvolution method to extract responses from each hemifeld of the display in order to explore differences in local responses and compare them to conventional global responses.
Methods :
Quasi-steady-state PERGs were recorded at 12.3rps from normal subjects under monocular and binocular conditions. Stimuli were delivered on two LED displays driven synchronously creating a single 30°x15°, (monofield) or asynchronously two separate 7.5°x15° or 15X15 fields (bifield). Patterns were 3 horizontal cycles (99% contrast). Subjects were asked to fixate along the center horizontal line at one of five points separated by 7.5°. Responses were from temporal or nasal retina depending on eye and fixation point. In the bifield case, bideconvolution was used to extract BiCLAD PERG responses from the corresponding display field. BiCLAD PERG were evaluated based on the N35, P50; and N95 components were analyzed using latency/amplitude measures. Responses from each of the retinal sections were compared with conventional PERG responses using the monofield case.
Results :
Both monofield and bifield conditions produced clearly distinquishable PERG waveforms. In both monocular and binocular conditions, nasal and temporal PERG responses showed small and consistent differences in amplitude and morphology. Nasal responses resembled a conventional PERG response, while temporal responses exhibited slightly bifurcated and smaller peaks. In bifield mode PERG components showed lateralization with respect to eye fixation.
Conclusions :
Hemifield testing using BiCLAD reveals differences in temporal and nasal morphology and will help in exploring retinal topography and enhancing the diagnostic utility of the PERG in retinal disorders. Since most retinal disorders begin in specific regions of the retina and propogate outwards, obtaining more spatially specific PERG responses has potential to increase the sensitivity and specificity of the technique in detect local deficits.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.