Comparison of Iridex MP3 and P3 probes on long-term intraocular pressure control after MicroPulse Transscleral-Cyclophotocoagulation

Abstract

PurposeMicropulse transscleral cyclophotocoagulation (MP-TSCPC) is a glaucoma procedure that delivers energy to the ciliary body with minimal collateral-damage. We aim to assess the long-term effectiveness of MP-TSCPC using the original MP3 and revised P3 probe. Methods and designBaseline Retrospective cohort study was performed to obtain baseline characteristics, intraocular pressure (IOP), number of IOP-lowering medications, and best-corrected visual acuity (BCVA) were obtained from pre- and post-operative visits of patients treated with MP-TSCPC. Failure was defined as IOP>21 mmHg, reduced IOP<20% below baseline, or IOP<5 mmHg on 2 consecutive follow-up visits after post-operative month 1, reoperation for glaucoma, or loss of vision to no light perception. ResultsA total of 113 eyes were enrolled, 44 using the MP3 probe and 69 with the revised P3 probe. Survival analysis found a 75% failure rate in patients treated with the revised P3 probe by the final visit with a mean time to failure (MTTF) of 4.8 ± 0.7 months which was higher than the original probe at 66% failure rate with a MTTF of 6.1 ± 1.1 months (p = 0.04). All causes of failure were due to high IOP and 67% required repeat treatment with MP-TSCPC or incisional surgery. Prior to censure of data from failure, both probes had significant reduction in IOP compared to pre-operative IOP at all time points. No significant changes in BCVA were found. Both groups were associated with low rates of complications. ConclusionBoth probes had a very low rate of visually significant complications when performed in a standardized method in accordance with surgical procedure and power settings recommended by Iridex; however, were associated with a high rate of single procedure failure due to uncontrolled IOP over the long term. The revised P3 probe was associated with a higher rate of failure. Patients experienced a reduction in IOP; however, a large proportion required additional treatment compared to the original MP3 probe.