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Effect of Operator and Optical Defocus on the Variability of Pattern Electroretinogram Optimized for Glaucoma Detection (PERGLA)

Vizzeri, Gianmarco MD; Tafreshi, Ali BS; Weinreb, Robert N. MD; Bowd, Christopher PhD

doi: 10.1097/IJG.0b013e31819f934e
Original Studies

Purpose To evaluate the effect of operator and optical defocus on the variability of pattern electroretinogram optimized for glaucoma detection (PERGLA).

Methods 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.

Results 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).

Conclusions 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.

Department of Ophthalmology, Hamilton Glaucoma Center, University of California, San Diego, La Jolla, CA

Supported by grant NIH EY018190.

Financial Disclosure: Carl Zeiss Meditec: Robert N. Weinreb (research support, consultant), Heidelberg Engineering: Robert N. Weinreb (research support), Lace Elettronica: Christopher Bowd (research support).

Reprints: Christopher Bowd, PhD, Department of Ophthalmology, Hamilton Glaucoma Center-178, University of California, San Diego, La Jolla, CA 92037-0946 (e-mail:

Received for publication October 22, 2008; accepted January 25, 2009

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