Efficacy and safety of subthreshold micropulse laser compared with threshold conventional laser in central serous chorioretinopathy

PURPOSE: To compare the efficacy and safety of subthreshold micropulse laser (SML) with threshold conventional laser (TCL) in central serous chorioretinopathy (CSC). METHODS: Prospective, randomized, double-masked, non-inferiority, 12-week clinical trial. Patients were randomly assigned 1:1 to SML group or TCL group. Patients in the SML group were treated with 577 nm micropulse laser. The spot size was 160 µm, the duty cycle was 5% and exposure time was 0.2 s. The power was 50% threshold tested. Patients in the TCL group were treated with 577 nm continuous laser. The power was 100% threshold tested. The primary outcome was the mean change in best-corrected visual acuity (BCVA) at week 12, with a non-inferiority limit of five letters on the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity charts. RESULTS: Eighty-eight patients were enroled. Seventy-seven patients were male. Forty-four patients were in SML group and 44 in TCL group. At week 12, SML was equivalent to TCL with a gain of 6.23 ± 8.59 and 6.61 ± 6.35 letters, respectively, (SML–TCL difference: −0.38 letters; 95% confidence interval (CI):−3.58–2.81; P(non-inferiority) = 0.0026). There was no statistically significant difference between the two groups (t = 0.240, P = 0.811). At week 12, the proportion of patients whose SRF had been totally absorbed was 63.63 and 81.82% respectively for SML and TCL groups. There was no statistically significant difference between the two groups (χ(2) = 3.67, P = 0.056). CONCLUSIONS: Both SML and TCL can improve visual acuity in CSC. SML was non-inferior to TCL in the improvement of BCVA.