While micropulse cyclophotocoagulation (MPCP) can lower intraocular pressure (IOP) in the short-term, a Journal of Glaucoma study shows that nearly half of patients require additional IOP-lowering intervention. Due to the potential for persistent complications, including those that affect visual acuity (VA), physicians should discuss the risks of MPCP thoroughly with patients, particularly those with mild glaucoma and good VA.

Traditionally, cyclodestructive procedures have been used to lower IOP in glaucoma patients who aren’t candidates for incisional surgery or who have poor visual potential. Transscleral diode laser cyclophotocoagulation (TSCPC) is a commonly used cycloablative procedure for patients with refractory glaucoma. Although it lowers IOP, it’s linked with complications such as prolonged inflammation, decreased vision, hypotony, loss of vision, and phthisis. Research speculates that these complications are due to damage to surrounding tissue during the continuous delivery of high-energy laser to the ciliary processes. MPCP uses a newer laser that delivers short, targeted bursts of energy, lessening the damage to surrounding tissues.

To evaluate the efficacy and complications of MPCP in a large series of patients with all stages of glaucoma, investigators reviewed patient charts from 3 clinical sites. MPCP was performed with 2000 mW energy, 31.3% duty cycle and 2 to 4 180-degree applications of 80 seconds duration each per treatment. The procedure was considered a failure if any of the following occurred: additional IOP lowering intervention, <20% IOP reduction from baseline at the last follow-up (with or without medication), or severe complications. The last follow-up was defined as the last available visit or the visit before further IOP lowering intervention, whichever occurred earlier. Severe complication was defined as loss of light perception, phthisis, or VA reduction of > 5 Snellen lines attributable to the laser treatment.


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In total, 167 eyes of 143 patients were included in the study. The mean age was 71 years, 53% were female, and 53% were Asian.; 60% of eyes had primary open angle glaucoma (POAG), 63% were pseudophakic, 38% had prior glaucoma surgery, and 51% had Snellen visual acuity (VA) of 20/40 or better. Mean follow-up time was approximately 11.9 months. Mean IOP was approximately 21.9 mm Hg before intervention, and 17.4 mm Hg at last follow-up (P <.0001). Researchers observed no change in mean logMAR VA (P =.0565) but 15% lost 3 or more Snellen lines of VA. 

The success rate was 36.5% (61/167 eyes) at last follow-up. The probability of survival was 82%, 71%, and 57% at 3, 6, and 12 months after the procedure, respectively. The reasons for failure were additional intervention in 47%, inadequate IOP reduction in 14%, and severe complication in 1.8%. Female sex was associated with a 56% decrease in failure rate compared with males (P <.0001), while a unit increase in baseline IOP corresponded with a 5.7% increase in failure rate (P <.0001). If repeat MPCP was allowed, then the success rate increased to 58%. There were no complications in 73% (122/167) but 11% (18/167) had persistent complications at the last follow-up and half of these 18 eyes had decrease in VA of 1 to 6 Snellen lines. Asian race (odds ratio 13.5, P =.0131) and phakic status (odds ratio 3.1, P =.0386) were associated with higher odds of developing mydriasis, which was the most common complication, according to the researchers.

“These findings are consistent with previous studies on MPCP which have reported success rates of 35% to 94% using various definitions of success and various laser treatment parameters,” according to researchers.

Researchers identified several limitations with their study, including its retrospective design and the lack of a comparison group. Also, the number of eyes available for analysis had decreased substantially by the 12 months follow-up time (44% of 167 eyes). In addition, the laser treatment protocol differed among surgeons and could have been modified during the study. 

Disclosure: Several study authors declared affiliations with the pharmaceutical and biotech industries. Please see the original reference for a full list of authors’ disclosures.

Reference

Radhakrishnan S, Wan J, Tran B, et al. Micropulse cyclophotocoagulation: a multicenter study of efficacy, safety, and factors associated with increased risk of complications. J Glaucoma. 2020 Dec;29(12):1126-1131. doi: 10.1097/IJG.0000000000001644.