The Impact of Clinical Success Levels on Postoperative RNFL Development After Trabeculectomy

Background: Trabeculectomy is the standard surgical treatment for advanced glaucoma, yet the relationship between postoperative intraocular pressure (IOP) and long-term structural preservation remains unclear. We investigated longitudinal changes in peripapillary retinal nerve fiber layer (RNFL) thickness following trabeculectomy in primary open-angle glaucoma and evaluated whether lower postoperative IOP levels are associated with improved structural stability. Methods: This retrospective consecutive case series included 106 eyes undergoing trabeculectomy between 2010 and 2020 with follow-up of up to 5 years. RNFL thickness was assessed using spectral-domain optical coherence tomography at baseline and during follow-up. IOP, glaucoma medication use, best-corrected visual acuity, and visual field mean defect were recorded longitudinally. Results: Mean IOP decreased from 23.8 ± 0.9 mmHg preoperatively to 10.5 ± 0.7 mmHg at 1 month and remained significantly reduced at 5 years (13.8 ± 0.7 mmHg), with sustained reduction in medication use. RNFL thickness declined significantly from 64.4 ± 2.0 µm during the first postoperative year to 57.2 ± 1.6 µm and subsequently remained relatively stable. While eyes achieving a postoperative IOP <12 mmHg showed no statistically significant RNFL thinning compared to baseline, eyes with higher postoperative IOP exhibited greater structural decline despite meeting conventional success criteria. Conclusions: Trabeculectomy provides durable IOP reduction; however, early structural loss may still occur. Our findings suggest that lower postoperative IOP levels may be associated with greater structural preservation, although this relationship requires further investigation.