Abstract
Purpose: :
To prospectively monitor progressive changes of retinal ganglion cell (RGC) function in early glaucoma using the pattern electroretinogram (PERG) as a surrogate measure.
Methods: :
Steady-state PERGs were recorded according to a user-friendly paradigm with skin electrodes and automated evaluation of amplitude and phase (Ophthalmology, 2004, 111:161-8). The method is reported to be highly reproducible between sessions and operators. Study subjects were 107 patients enrolled as glaucoma suspects or early manifest glaucoma at their initial visit. All patients underwent longitudinal PERG tests (average n= 10.7 ± 3.2) as well as Humphrey Perimeter Central 24-2 program (SAP) tests (average n= 9.68 ± 2.89) over 6-8 years. PERG amplitude and phase were normalized for physiological age-related changes and linear regressions fitted to the data to calculate slopes (signal), slope SE (noise), and corresponding signal-to-noise ratios (SNR). Linear regressions were also used to fit SAP measures of global indices mean deviation (MD) and pattern standard deviation (PSD).
Results: :
For both right eyes and left eyes, slopes of PERG amplitude/phase were skewed toward negative values, their mean being significantly different from zero (P<0.01). In contrast, mean slopes of SAP-MD and PSD were not significantly different from zero. In a substantial number of eyes (PERG amplitude: 17%, PERG phase: 23-30%) negative slopes were significant (P < 0.05). Few eyes displayed significant progression of SAP-MD (1-3%) and SAP-PSD (4-6%), and most of SAP-progressing eyes also progressed with PERG (PERG amplitude & SAP-MD, ~1-2%; PERG amplitude & SAP-PSD, ~2-3%; PERG phase & SAP-MD, ~1-3%; PERG phase & SAP-PSD, ~2%). SNR were significantly higher for PERG than SAP: PERG amplitude mean (SD) = 0.9 (1.5); PERG phase = 1.4 (1.7); SAP-MD =0.24 (1.25); SAP-PSD = 0.0 (1.4).
Conclusions: :
A key question in glaucoma follow-up is whether and to what degree the disease progresses over time. The PERG recorded with the user-friendly PERGLA paradigm displayed clear longitudinal loss of signal (diminished amplitude, phase delay) in a substantial number of eyes of patients, indicating progressive deterioration of RGC function. Progression of SAP global indices MD and PSD was found in a relatively smaller number of eyes, and most often in association with PERG progression. The PERG, compared to SAP, appears to have substantially higher SNR for detecting progression of RGC dysfunction in early glaucoma.
Keywords: ganglion cells • clinical (human) or epidemiologic studies: natural history • electroretinography: clinical