Correlation between mid-term intraocular pressure and aqueous flare value in micropulse transscleral cyclophotocoagulation: a retrospective observational study

Micropulse transscleral cyclophotocoagulation (MP-TSCPC) lowers intraocular pressure (IOP), but the mechanisms underlying its IOP-reducing effect remain incompletely understood. Although early postoperative flare elevation has been reported in association with IOP reduction, the relationship during the mid-term postoperative period has not been well characterized. In this study, the mid-term period was defined a priori as 3–18 months after surgery. This retrospective exploratory study included 25 eyes of 25 patients who underwent initial MP-TSCPC at Ishida Eye Clinic between March 2019 and May 2022 and had available postoperative flare measurements. Aqueous flare was assessed using a laser flare meter, and IOP was measured primarily by Goldmann applanation tonometry. Flare increase ratio (%) and IOP reduction ratio (%) were calculated relative to baseline. Associations were evaluated using Spearman’s rank correlation coefficient. To account for multiple comparisons across postoperative time points, p-values were adjusted using the Benjamini–Hochberg procedure, primarily considering a false discovery rate (FDR) threshold of 0.05; findings at FDR < 0.10 were interpreted as exploratory. The mean age was 80.4 ± 10.3 years. The mean preoperative IOP was 17.6 ± 6.9 mmHg, and the mean preoperative flare value was 13.9 ± 7.7 photon counts/ms. Postoperative IOP showed significant reductions at 1 and 12 months, and flare values were significantly elevated at multiple time points through 24 months. Significant positive correlations between flare increase ratio and IOP reduction ratio were observed at 3 months (ρ = 0.54, p = 0.026), 18 months (ρ = 0.964, p = 0.0027), and at the final visit (ρ = 0.41, p = 0.022). After adjustment for multiple comparisons, only the 18-month correlation remained significant at FDR < 0.05 (q = 0.022), whereas the correlations at 3 months (q = 0.069) and at the final visit (q = 0.088) were significant at FDR < 0.10 and were therefore considered exploratory. In this small exploratory cohort, sustained postoperative aqueous flare elevation was associated with greater mid-term IOP reduction after MP-TSCPC. However, given the limited sample size and observational design, these findings should be interpreted cautiously, and causal mechanisms cannot be established. Approval Number: R2025063 (University of Toyama Ethics Committee). Registration date: July 10, 2025.