Electrophysiological Changes Before and After Glaucoma Filtration Surgery in the Mid-Postoperative Period: A Retrospective Study

Introduction Changes in retinal function during the first days after glaucoma filtration surgery have been documented with electroretinography (ERG), but little is known about later time points, particularly in eyes operated on without concurrent cataract surgery and in eyes that develop choroidal detachment (CD). We examined ERG parameters before and after filtration surgery performed alone and explored, as a hypothesis-generating analysis, whether the responses differed between eyes with and without postoperative CD. Methods Thirty-two eyes of 32 patients who underwent filtration surgery alone at Chiba University Hospital were reviewed retrospectively. Full-field ERGs were recorded with dilated pupils before surgery and 41.9 ± 18.3 days afterward using the RETeval system (LKC Technologies, Gaithersburg, MD), with the light-adapted 3.0 and dark-adapted 0.01 stimuli specified by the International Society for Clinical Electrophysiology of Vision (ISCEV) standard. Amplitudes and peak times of the photopic a- and b-waves and the scotopic b-wave were compared using the Wilcoxon signed-rank test, and eyes were grouped according to the presence or absence of CD. Results Across the whole cohort, no amplitude or peak time changed significantly. In the CD group, the scotopic b-wave peak time shortened from 120.9 ± 12.0 ms to 114.6 ± 7.8 ms (p = 0.025), while the remaining parameters were unchanged; the non-CD group showed no significant change. Intraocular pressure (IOP) fell from 18.4 ± 4.4 to 8.3 ± 3.5 mmHg after surgery (p < 0.001). Conclusions Roughly six weeks after filtration surgery performed alone, ERG amplitudes were unchanged. This is compatible with a limited electrophysiological effect of surgery at this stage or with recovery from changes that occurred earlier, although the design does not allow the two to be distinguished. The shortening of the scotopic b-wave peak time in eyes with CD was an exploratory observation in eight eyes and requires confirmation in larger prospective studies.