Acquisition and Analysis of High Rate Pattern Electroretinograms

The first investigations into the electrophysiology of the retina were published over 80 years ago (Kahn and Löwenstien, 1924). In the decades since, electroretinography (ERG) has become a widely used tool in ophthalmology for monitoring the health of the visual system. Different variations of the ERG, such as flash ERG (FERG) and pattern ERG (PERG) can be used to isolate the response of the various cellular generators, giving an overall view of retinal health. Currently, there are a number of visual display units (VDUs) available for eliciting the wide array of ERG responses. These VDUs range from conventional CRT and LCD displays, to digital micro-mirror devices, to laser interferometer based systems. Unfortunately, many of the VDUs available are limited in the way they display visual stimuli, particularly when it comes to precise timing control. In order to perform advanced signal analysis techniques, such as the recently developed Continuous Loop Averaging Deconvolution (CLAD) technique, on ERG responses it is crucial to ensure precise delivery of stimuli with sub-millisecond accuracy. CLAD is capable of extracting additional information from ERG responses, which has the potential of increasing the diagnostic value of the response, particularly at high stimulation rates. Unfortunately, conventional VDUs are not able to take advantage of the technique. For this dissertation, a number of high rate pattern reversal VDUs were designed and developed which would allow for the application of the CLAD technique to the PERG response. Using these specially designed displays in conjunction with CLAD, it was shown that individual waveform components, normally lost as stimulation rates exceed 6 reversals per second (Bach et al., 2012), could be retrieved regardless of the stimulation rate used. This study also investigated the rate based effects of the PERG response. It was shown that as stimulation rates are increased the conventional PERG response morphology changes to reveal new high rate waveform components. The individual waveform components of the PERG response are used to diagnose and monitor a number of degenerative retinal disorders such as glaucoma. The ability to extract these components at higher rates can potentially improve the diagnostic value of the PERG by detecting dysfunction earlier. Additionally, the new, high rate waveform components might provide insight into the detection of other retinal maladies