Abstract
Purpose :
To study retinal function in glaucoma using a light-adapted full-field ERG luminance-response series.
Methods :
Nine patients (n=9 eyes) with primary open-angle glaucoma but preserved visual acuity and no other ocular disease were evaluated. Visual field test (Humphrey – Zeiss; SITA-Fast 24-2) and spectral-domain optical coherence tomography (Heidelberg) measuring peripapillary retinal nerve fiber layer thickness (RNFL) were performed. Full-field ERGs (RETeval, LKC) were measured using skin electrodes and fully dilated pupils with a short photopic hill protocol consisting of a 30 cd/m2 background and a sequence of 8 flash stimuli logarithmically spaced from 0.1 to 22 cd.s/m2. b-wave amplitude data as a function of flash strength were fit with a Gaussian to determine maximal b-wave amplitude (Vmax), flash strength at Vmax (x0), and width of the Gaussian component (w). Data were compared with 9 healthy subjects (control) in the same age range.
Results :
All subjects showed visual acuity of 20/20, visual field mean deviation was -5.5 ±1.7 dB and RNFL thickness 93.5 ± 16.5 µm. Comparing glaucoma subjects to controls (mean SEM), the following measurements did not show a statistically significant difference: dilated pupil diameter 6.6 ± 0.35 mm vs. 6.8 ± 0.3 mm (p=0.3), and x0 6.4 ± 0.9 cd.s/m2 vs. 4.4 ± 0.8 cd.s/m2 (p=0.1). In contrast, these measures did show differences: Vmax 22.5 ± 3.8 µV vs. 36.2 ± 3.7 (p=0.02), and w 8.2 ± 0.5 cd.s/m2 vs. 5.0 ± 0.5 cd.s/m2 for controls (p=0.0006 - figure 1). No significant correlation was found between photopic hill parameters and pupil size, visual field MD, age or RNFL thickness.
Conclusions :
Parameters derived from luminance-response series, which measure cone-driven function, show differences in subjects with early glaucoma. While our sample size is small, the width of the ERG photopic hill shows promise in the early detection of glaucoma.
This is a 2020 ARVO Annual Meeting abstract.