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Nakita Ryan, Gabrielle Hodder, Lauren King, James Drover; A Comparison of Electrophysiological and Behavioral Measures of Visual Acuity. Journal of Vision 2017;17(10):440. doi: https://doi.org/10.1167/17.10.440.
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© ARVO (1962-2015); The Authors (2016-present)
Unlike behavioral techniques, the measurement of visual evoked potentials (VEPs) provides an objective electrophysiological measure of vision directly from the visual cortex. The purpose of the present study is to provide the first comparison of visual acuity scores obtained using a new VEP system and those obtained using behavioral tests. Grating acuity was estimated in 27 participants (M = 21.2±1.5 years) using the VeriSci Neucodia VEP system following the sweep VEP (sVEP) procedure. During each 10 second sweep, participants were presented with 8 horizontal square wave gratings ranging from 5.3 to 35.6 cpd (0.75 to -0.07 logMAR). Each participant completed 8 sweeps. Grating acuity was also measured using the Teller Acuity Cards II (TAC) and optotype acuity was estimated using the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity test. Scores from the three tests were compared. In addition, coefficients of repeatability (COR) were determined for all possible test pairs in order to determine level of agreement. Friedman analyses revealed a significant test effect (p< 0.0001). Specifically, ETDRS scores were significantly finer than scores obtained with sVEP (-0.04 v. 0.12 logMAR, p< 0.0001) and the TAC (-0.04 v. 0.11 logMAR, p< 0.0001). TAC and sVEP scores did not differ (TAC=0.11 logMAR; VEP=0.12 logMAR; p=0.52). COR analyses indicated that the level of agreement between all test pairs was poor and virtually identical (TAC and sVEP COR=0.30 logMAR; sVEP and ETDRS COR=0.30 logMAR; TAC and ETDRS COR=0.31 logMAR). The poor agreement between tests is not surprising given that they assess different visual abilities (i.e., TAC and sVEP: resolution acuity; ETDRS: recognition acuity). Furthermore, the tests likely tap different underlying neural mechanisms as VEPs are recorded directly from the visual cortex, whereas the TAC and the ETDRS require a behavioural response and therefore, likely tap mechanisms further upstream within the visual system and beyond.
Meeting abstract presented at VSS 2017
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