Use of extended protocols with nonstandard stimuli to characterize rod and cone contributions to the canine electroretinogram.

Purpose: In this study, we assessed several extended electroretinographic protocols using nonstandard stimuli. Our aim was to separate and quantify the contributions of different populations of retinal cells to the overall response, both to assess normal function and characterize dogs with inherited retinal disease.
Methods: We investigated three different protocols for measuring the full-field flash electroretinogram-(1) chromatic dark-adapted red and blue flashes, (2) increasing luminance blue-background, (3) flicker with fixed frequency and increasing luminance, and flicker with increasing frequency at a fixed luminance-to assess rod and cone contributions to electroretinograms recorded in phenotypically normal control dogs and dogs lacking rod function.
Results: Temporal separation of the rod- and cone-driven responses is possible in the fully dark-adapted eye using dim red flashes. A- and b-wave amplitudes decrease at different rates with increasing background luminance in control dogs. Flicker responses elicited with extended flicker protocols are well fit with mathematical models in control dogs. Dogs lacking rod function demonstrated larger amplitude dark-adapted compared to light-adapted flicker responses.
Conclusions: Using extended protocols of the full-field electroretinogram provides additional characterization of the health and function of different populations of cells in the normal retina and enables quantifiable comparison between phenotypically normal dogs and those with retinal disease.
(© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)