To evaluate the effect of operator and optical defocus on the variability of pattern electroretinogram optimized for glaucoma detection (PERGLA).
Two different operators obtained 2 PERGLA recordings each from 10 healthy participants (5 women, mean age 32.1±10.3 y). In addition, one of the operators obtained recordings in which corrective lenses of various diopters (±0.5, ±1, ±2, and ±3) were used to generate optical defocus in both eyes. The effect of operator on PERGLA amplitude and phase variability was determined using a single nested variance components' analysis model and by using Bland-Altman plots. One-way analysis of variance (ANOVA) was used to determine the effect of optical defocus on amplitude and phase.
Differences in measurements between operators accounted for approximately 26.6% and 18.2% of the total variance for amplitude and phase, respectively. Results were confirmed by the use of Bland-Altman plots. ANOVA identified a significant effect of defocus on mean amplitude (F=2.65, P=0.01), but not phase (F=1.02, P=0.42).
Measurements obtained by different operators can result in significant differences in PERGLA amplitude. In addition, although optical defocus leads to a decrease in PERGLA amplitude by reducing visual acuity, this can be avoided by obtaining J1 or better vision before testing.