Dose-effectiveness Optimizing in Micropulse Transscleral Cyclophotocoagulation: A Cohort Study in Refractory Glaucoma

To characterize the clinical outcomes, safety profile, and dose-response relationship of micropulse transscleral cyclophotocoagulation (MPCPC) utilizing augmented dose protocols in Chinese patients with refractory glaucoma.

Retrospective, single-center study.

Patients treated with MPCPC at Zhongshan Ophthalmic Center from August 2022 to August 2024.

Laser parameters of MPCPC were standardized at 2000 mW and a 31.3% duty cycle, with patients stratified into three groups based on treatment duration: 160 seconds, 200 seconds, and 240 seconds.

Participants were followed up for 12 months to assess changes in best-corrected visual acuity (BCVA), intraocular pressure (IOP), and number of antiglaucoma medications. Treatment success was defined as a final IOP between 5 and 21 mmHg or a ≥ 20% reduction from baseline, without the need for increased antiglaucoma medications or surgical re-intervention.

A total of 229 eyes from 229 patients were analyzed: 160 s (n=66), 200 s (n=35), and 240 s (n=128). At 12 months postoperatively, the 240 s group achieved a 38.7% IOP reduction, which was significantly superior to the 25.5% reduction observed in the 160 s group (P=0.028). Linear regression identified a significant dose-effect, with each 40-second increment in laser duration associated with an additional 5.9% IOP reduction (β=0.059, P=0.035). Kaplan-Meier survival analysis revealed the highest cumulative success probability in the 240 s group (68.7%), followed by the 200 s group (58.1%) and the 160 s group (53.6%) (P=0.040). Multivariate Cox regression confirmed that eyes with shorter treatment duration and eyes with longer axial length had a higher risk of treatment failure (P<0.05). Notably, a decline in visual acuity occurred only in the 160 s group (P=0.036). The number of antiglaucoma medications was significantly reduced in all three groups compared with baseline (P<0.01). Complication rates did not differ significantly among the three groups (P=0.155).

MPCPC constitutes a safe and potent modality for IOP reduction, exhibiting a dose-dependent effectiveness. The augmented-dose protocols of 200-240 s seem to optimize long-term IOP control. Patients with longer axial length have a potential risk of treatment failure, which is likely attributable to posterior displacement of the ciliary body.