Pattern electroretinogram progression in glaucoma suspects.

Purpose: To prospectively monitor progressive changes of retinal ganglion cell function in early glaucoma using the pattern electroretinogram (PERG).

Methods: Fifty-nine patients enrolled as glaucoma suspects were observed untreated over an average of 5.7±1.4 years, during which they were tested with PERG (PERGLA paradigm) and standard automated perimetry (SAP) 2 times per year. PERG amplitude and phase were normalized for physiological age-related changes, and linear regressions fitted to the data to calculate progression slopes (signal), slope SE (noise), and corresponding signal-to-noise ratios (SNR=slope÷SE). Linear regressions were also used to fit SAP global indices mean deviation (MD) and pattern standard deviation (PSD).

Results: On average, progression slopes of PERG amplitude/phase were skewed toward negative values, their mean being significantly (P<0.01) different from zero. In contrast, mean slopes of SAP-MD and PSD were not significantly different from zero. SNRs were higher for PERG than SAP (P<0.01). A substantial number of eyes displayed significant (P<0.05) progression of PERG amplitude (15% to 20%) or PERG phase (16% to 25%). Fewer eyes displayed significant progression of SAP-MD (0% to 2%) or SAP-PSD (4% to 8%).

Conclusions: The PERG displayed clear longitudinal loss of signal (diminished amplitude, phase delay, or both) in a substantial number of eyes of patients, indicating progressive deterioration of retinal ganglion cell function. Progression of SAP global indices MD and PSD was found in a relatively smaller number of eyes. It remains to be established whether PERG progression has predictive value for developing visual dysfunction.