Combined viscocanalostomy and retrabeculotomy versus retrabeculotomy for management of refractory primary congenital glaucoma: a comparative study.

BACKGROUND: To evaluate and compare the long-term clinical outcomes of combined viscocanalostomy and repeat trabeculotomy (VCO+retbo) versus repeat trabeculotomy alone (retbo) in eyes with primary congenital glaucoma (PCG) that failed initial angle surgery. METHODS: This prospective comparative study evaluated 164 eyes with PCG that exhibited an insufficient response to primary trabeculotomy, divided into VCO+retbo (n = 82) and retbo (n = 82) groups. Treatment success was defined as an intraocular pressure (IOP) between 6 and 21 mmHg with a ≥ 20% reduction from baseline, categorized as complete (medication-free) or qualified (with medications). Overall treatment failure served as the principal comparative outcome, whereas complete/qualified success rates and final medication burden were designated as secondary exploratory endpoints. RESULTS: The mean follow-up duration was 30.36 ± 13.38 months. Regarding the principal outcome, overall failure rates did not differ significantly between groups (31.7% for VCO+retbo vs. 37.8% for retbo; p = 0.219), nor did Kaplan-Meier cumulative survival (log-rank p = 0.290). In multivariable Cox regression, baseline IOP > 30 mmHg prior to second surgery was the sole independent predictor of failure (HR = 2.33, 95% CI: 1.33-4.11, p = 0.003), whereas surgical technique was not predictive. For secondary outcomes among successfully controlled eyes, final IOP did not differ significantly between groups (16.20 ± 2.94 mmHg vs. 17.67 ± 4.35 mmHg). However, the retbo group maintained control with significantly fewer topical medications (0.98 ± 1.10 vs. 2.04 ± 1.03, p < 0.001). Complete success was achieved in 32.9% of retbo eyes compared to 9.8% of VCO+retbo eyes, whereas qualified success was 29.3% versus 58.5%, respectively (p < 0.001). CONCLUSIONS: No statistically significant difference in overall treatment failure was detected between VCO+retbo and retbo in refractory PCG. Repeat trabeculotomy alone was associated with a higher rate of medication-free success and lower medication burden; these secondary exploratory findings require confirmation in prospective randomized trials with standardized prescribing protocols. ETHICS APPROVAL: The study was approved by the local ethics committee of Tehran University of Medical Sciences (IR. TUMS. FARABIH. REC. 1402.009). The online version of the decree is publicly available at: https://ethics. RESEARCH: ac.ir/IR.TUMS.FARABIH.REC.1402.009 Trial registration: This study was not registered in a clinical trial registry. Per our institution's standard practice, prospective registration is reserved for randomized controlled trials; as both surgical techniques compared here are routine, established procedures rather than novel or experimental interventions, the study proceeded under institutional ethics approval alone. CLINICAL TRIAL NUMBER: Not applicable.