sVEPs are generally used to rapidly obtain visual acuity. Several studies have determined the reliability of acuity measurements with psychophysical techniques. The aim of this study was to determine the intersession and intrasession variabilities of sVEP measurements. Twenty-four normal, adult subjects took part in this project. Stimulus production and data analyses were done using an Enfant 4010. Standard VEP recording techniques were employed. Data were collected on two separate days (at least 1 week apart). At each visit, two complete sets of sVEP data were collected and averaged. A logMAR acuity chart was also used to determine the acuity at each visit. Paired t tests, 95% confidence intervals, intraclass correlation coefficients, and coefficients of repeatability were used to determine whether there was a difference in the intrasession and intersession acuities. The mean acuity difference and coefficient of repeatability were +0.01 and 0.191 for visit 1 and −0.019 and 0.186 for visit 2, respectively. The mean acuity difference and coefficient of repeatability across visits were +0.008 and 0.176 for the first acuity and−0.02 and 0.170 for the second acuity, respectively. Paired t tests did not find a significant difference between any set of data or the average for visits one and two (all P values > 0.05). The intraclass correlation coefficients comparing the average sVEP data and the logMAR data for visits 1 and 2 were 0.71 and 0.88, respectively. The coefficients of repeatability for the averaged sVEP acuity and the logMAR acuity for the two visits were 0.11 and 0.07, respectively. The repeatability of the sVEP acuity estimate in a large population of adults is similar to that of previous published reports on infants and is nearly as high as that of logMAR acuity chart data. The repeatability is the same for single best estimates of acuity and averaged estimates of acuity across visits.
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