Longitudinal Retinal Layer Changes After Deep Sclerectomy in Primary Open-Angle Glaucoma: A Three-Year Retrospective Cohort Study Using Spectral-Domain OCT

Background: To evaluate longitudinal peripapillary and macular retinal layer changes over three years before and after deep sclerectomy (DS) in eyes with primary open-angle glaucoma (POAG). Methods: This retrospective monocentric study included 150 eyes undergoing DS with intraoperative mitomycin C. Cohort 1 (n = 111) was analyzed for absolute retinal layer thickness changes and cohort 2 (n = 39) for pre- and postoperative thinning rates using spectral-domain OCT. Intraocular pressure (IOP), medication use, best-corrected visual acuity (BCVA), and visual field mean defect (MD) were assessed over three years. Results: Mean IOP decreased significantly at three years in both cohorts (cohort 1: 22.8 ± 0.7 to 14.9 ± 0.7 mmHg; cohort 2: 20.8 ± 1.2 to 13.5 ± 0.9 mmHg; both p < 0.001), alongside a significant reduction in medication use (p < 0.001). BCVA remained stable, whereas MD worsened significantly in a mixed-effects model (cohort 1: +0.70 dB/year, p = 0.002; cohort 2: +0.74 dB/year, p < 0.001). Despite sustained IOP reduction, mean peripapillary RNFL thickness declined (cohort 1: 60.1 ± 1.4 to 56.6 ± 1.8 µm, p < 0.001; cohort 2: 61.1 ± 2.4 to 57.4 ± 2.9 µm, p = 0.005). In cohort 2, the macular RNFL thinning rate decreased numerically after surgery (−1.40 ± 0.67 to −0.08 ± 0.47 µm/year; difference 1.32 µm/year, 95% CI −0.28 to 2.92; p = 0.11). Macular layers showed no significant changes. Conclusions: DS achieved sustained IOP reduction with stable visual acuity, but visual field MD worsened over three years. Peripapillary RNFL thinning persisted postoperatively, though macular thinning rates showed a non-significant reduction. Structural monitoring remains necessary after glaucoma surgery despite adequate IOP control.