Abstract
Purpose :
A PERG stimulus source was developed to evaluate the retina beyond approximately 25 degrees of visual angle (Patangay et al., TVST 2018;7(1):8). Local areas of functional deficit in the peripheral retina may not result in a measurable reduction in the global peripheral PERG (pPERG) response. Recording from local areas, or sectors, of the retina can increase sensitivity to local dysfunction, but at the cost of extending testing time as each area of retina is probed sequentially. Here we describe an approach for obtaining responses from two sectors of the peripheral retina simultaneously.
Methods :
All recording was from healthy eyes using DTL electrodes. The pPERG stimulus was divided into superior and inferior sectors, each stimulating a “half-ring” of the peripheral retina. Each sector was stimulated separately, then together but at slightly different pattern reversal rates. During simultaneous stimulation, a mixed response was obtained and then separated into superior- and inferior-sector responses by windowing the mixed response according to the reversal rate relevant to that sector. To ensure that the sector responses recovered from the mixed signal were correct, the mean ON luminance of the inferior sector was varied while that of the superior sector was held constant.
Results :
When recorded simultaneously and then recovered via appropriate windowing, response amplitudes in each sector were similar to those obtained when stimulating the sectors separately. Increasing the luminance of the inferior sector (46, 192, 672 ph cd m-2) while holding that of the superior sector constant (192 ph cd m-2), yielded recovered response amplitudes that increased for the inferior sector, and decreased slightly for the superior sector (consistent with global light adaptation). The mean signal to noise ratios (SNRs) of the sector responses when recorded simultaneously, or separately, were 19.9 and 17.4 dB, respectively, when averaging over 600 pattern reversals for each sector and recording condition.
Conclusions :
A method for simultaneously acquiring unique responses to two sectors of a PERG stimulus field has been demonstrated. The SNR of the waveforms obtained with simultaneous sector recording was slightly greater than that obtained with separate recording of each sector and obtained in approximately one-half the time.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.