Abstract
Purpose :
The pattern electroretinogram (pERG) response reflects, in part, ganglion cell function. Conventional pERG stimulates the central 20-30 degrees of visual field, however, early effects of glaucoma may occur outside of this region. Our hypothesis is that a test of ganglion cell function that probes the peripheral retina could prove more sensitive to the earliest stages of disease. Here a high-luminance pattern stimulus is presented to the far-peripheral retina (ppERG) and evaluated for relative efficacy in glaucoma compared to conventional pERG.
Methods :
Seven normally-sighted subjects, four mid-stage patients (HVF mean deviation -3.7 to -7.0, at least one OCT sector outside normal limits), and one early-stage patient (HVF -2.2, one OCT sector borderline) were recruited. A hemispherical surface was used to present a reversing checkerboard pattern (10 degree checks, 4.6 reversals per second) to the peripheral retina, from approximately 20 degrees to the visual field limit in all directions (ring stimulus) or in three sectors that map to superior, nasal and inferior sectors at the optic nerve head. Pattern ON-luminance was approximately 15X the ISCEV-recommended minimum. Conventional pERG responses (ISCEV-recommended protocol) were recorded on the same day for comparison. Using amplitudes and implicit times of P and N waveform components, a cluster analysis was performed to evaluate sensitivity of each test.
Results :
Sensitivity and specificity were 66.7% and 75.0%, respectively, for conventional pERG, and were both 100% for ppERG. The distance-from-healthy-mean measure used in the cluster analysis was nearly the same for normal and patient groups for the pERG test (mean +/- SD = 7.1+/-2.3 vs. 7.7+/-2.9), but provided strong separation for the ppERG test (6.7+/-1.9 vs. 27.2+/-11.0). Proof of concept for sector stimulation in healthy eyes was demonstrated.
Conclusions :
High-luminance peripheral-field pattern stimulation shows promise as a test with high sensitivity to glaucoma, with possible advantage for early-stage disease. Sector stimulation may exploit the asymmetric damage associated with early glaucoma, and better correlate with retinal nerve fiber layer thickness measurements at the optic disk.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.