Evaluation of Peak Intraocular Pressure Reduction in the Water-Drinking Test and Safety of Subliminal Subthreshold Laser

Abstract

Purpose:

To evaluate the efficacy and safety of subliminal subthreshold laser (SubCyclo) in reducing peak intraocular pressure (IOP) using the water-drinking test (WDT) in patients with refractory glaucoma.

Methods:

This prospective interventional study included 50 eyes of 49 patients with moderate-to-advanced refractory glaucoma treated with SubCyclo using a standardized protocol. WDT was performed at baseline, 1, 3, and 6 months postoperatively. Surgical success was defined as: Criterion A, IOP < 21 mmHg or ≥ 20% reduction from baseline; and Criterion B, IOP < 21 mmHg and ≥ 20% reduction. The number of medications, reasons for patient exclusion, and sensitivity analyses comparing patients with ≥ 3 months versus < 3 months follow-up were assessed. Safety outcomes included complications and hypotony.

Results:

Mean baseline basal and peak IOP was 23.2 ± 8.9 mmHg and 27.8 ± 11.1 mmHg, respectively. At 6 months, basal IOP was 20.1 ± 8.6 mmHg (13.5% reduction, P = 0.18), and peak IOP was 25.8 ± 10.3 mmHg (7.2% reduction, P = 0.73). Surgical success at 6 months was 38% (criterion A) and 20% (criterion B). Kaplan–Meier analysis showed cumulative failure rates of 64.8% and 81.5%, respectively. Mean medications decreased from 4.1 ± 1.02 to 3.72 ± 1.40 (P = 0.34) at 6 months. No hypotony, vision-threatening complications, or persistent inflammation were observed.

Conclusion:

SubCyclo showed a favorable safety profile, but did not significantly reduce peak IOP as measured by WDT in refractory glaucoma. These findings highlight the need to refine treatment parameters and identify subgroups most likely to benefit.