A New Pattern Electroretinogram Paradigm Evaluated in Terms of User Friendliness and Agreement with Perimetry
Received 3 April 2006; accepted 31 July 2006.
Purpose
To assess ease of use of the pattern electroretinogram optimized for glaucoma screening (PERGLA) paradigm by a novice operator; to study test–retest variability of the PERGLA parameters; and to compare results from the PERGLA to those from perimetry.
Design
Cohort study.
Participants
Twelve healthy control subjects and 16 patients with moderate to advanced glaucoma in at least 1 eye.
Methods
Pattern electroretinograms were recorded simultaneously from both eyes using a commercially available testing station. Each participant underwent PERGLA procedures in 2 sessions. One eye of each subject was tested on contrast sensitivity perimetry (CSP) in which a 0.4 cycles/degree Gabor patch served as a stimulus. Central visual fields results from conventional automated perimetry (CAP) were obtained from patients’ records. Bland–Altman analysis was performed on PERGLA results to assess normal test–retest variability. Differences from mean normal (in decibels [dB]) were compared for PERGLA versus CSP and CAP.
Main Outcome Measures
Pattern electroretinogram amplitude, noise, phase, and test–retest variability (coefficient of variation); contrast sensitivity from CSP; perimetric sensitivity from CAP; and differences from mean normal for PERGLA, CSP, and CAP.
Results
The mean log amplitude (0.08±0.12 log μV) and the mean phase (1.92±0.07 π rad) for the control group were consistent with published PERGLA norms, as was test–retest variability for both amplitude (coefficient of variation [CV] = 8.2±7.0%) and phase (CV = 1.1±0.9%). The mean signal-to-noise ratio (8.7±4.5) was lower than published norms. The test–retest variability increased as PERGLA log amplitude decreased (R2>0.12, P<0.05). On average, differences from mean normal were similar for PERGLA versus CSP and for PERGLA versus CAP (mean differences<0.5 dB) with 95% confidence intervals near ±4 dB in both comparisons.
Conclusions
A novice operator successfully replicated published PERGLA norms in a young control group for amplitude, phase, and repeatability. Higher test–retest variability was found in eyes with smaller signals. On average, PERGLA results were in reasonable agreement with those from perimetry, although there existed large individual differences which may limit the usage of PERGLA in screening or in following progression of glaucoma.
State University of New York, State College of Optometry, New York, New York.
Correspondence to Andrea Yang, OD, State University of New York, State College of Optometry, 33 West 42nd Street, New York, NY 10036.
Manuscript no. 2006-396.
Supported by National Institutes of Health, Bethesda, Maryland (grant no. NIH EY 007716).
The authors have neither commercial nor proprietary interest in the equipment used in the study.
ABSTRACT