Abstract
Electroretinograms (ERGs) are biopotentials from the retina which serve as the inputs to the visual system. As conventionally acquired, ERG responses give a single global response, however, neuroanotomical asymmetry of the retina suggests local ERG responses may differ from this global response. Many forms of retinal dysfunction manifest in specific regions and the ability to extract more localized ERG responses has the potential to improve such techniques. Currently, topographical measures are obtained either by altering fixation of the subject across sessions or with multi-focal ERG which uses a very wide range of rates. In this study we have developed a new bi-field orthogonal stimulation methodology which allows for the extraction of responses from the temporal and nasal portions of the retina using deconvolution methods. During recordings, subjects focused on one of five fixation points along the bifield pattern stimulation display. Responses were collected at two different mean rates (2.5 and 12.5 rev/sec). The two fields of the display were driven with orthogonal reversal sequences with similar mean rates, but slightly different temporal jitters. This allowed for the extraction of two independent pattern ERG responses (nasal and temporal) from each eye using continuous loop deconvolution (Ozdamar et al., 2014; Toft-Nielsen et al., 2014). Responses were analyzed using latency/amplitude measures. Responses obtained at the two rates exhibited conventional transient PERG peaks (N35, P50, N95). All peaks were clearly distinguishable against noise levels. Nasal and temporal responses showed clear differences in amplitude and subtle differences in morphology (narrowing of peaks and increase in higher spectral content) which were consistent across subjects. Response quality and consistency in morphology across subjects suggests that simultaneous recording of bifield (nasal/temporal) PERG is possible. Differences in temporal and nasal morphology may have significance in exploring retinal topography and could enhance the diagnostic utility of PERG in visual disorders.