Purpose: To compare the efficacy and safety of micropulse transscleral cyclophotocoagulation applied at the level of the pars plicata transscleral micropulse cyclophotocoagulation (PLI-MPC) versus the pars plana transscleral micropulse cyclophotocoagulation (PLA-MPC).

Methods: This prospective interventional case series included 44 eyes of 31 medically treated primary open-angle glaucoma patients scheduled for micropulse transscleral cyclophotocoagulation to achieve further intraocular pressure (IOP) reduction. In total, 22 eyes underwent PLI-MPC and PLA-MPC each. Primary endpoints were the reduction of 24-hour mean diurnal IOP (mean of 6 measurements), diurnal IOP fluctuations, and peak IOP, after 3 and 12 months. Secondary outcomes were postoperative complications, a possible deterioration in visual acuity and field, factors influencing IOP reduction, and the number of dropouts.

Results: In the PLI-MPC group, IOP was reduced from 15.9±3.4 mm Hg to 13.6±3.1 mm Hg (n=16; P<0.001) and 12.9±3.7 mm Hg (n=13; P<0.001) at 3 and 12-month follow-up. In the PLA-MPC group, IOP decreased from 16.4±3.5 mm Hg to 12.3±2.6 mm Hg (n=15; P<0.001) and 11.8±2.2 mm Hg (n=14; P<0.001), respectively. At 12 months, 59% of the PLI-MPC and 63% of the PLA-MPC group had a sufficient IOP reduction to reach the individual target pressure. No complications were seen in either group. A higher preoperative IOP was recognized as the only factor influencing the postoperative IOP reduction.

Conclusions: PLI-MPC and PLA-MPC seem to be safe and effective in further lowering the IOP in about 60% of patients with primary open-angle glaucoma who did not reach target pressure despite maximally tolerated IOP-lowering medication. Although the IOP-lowering effect was not statistically significantly different between groups the pars plicata application was superior and easier to perform and should be recommended as the preferred method of application.