A systematic review of cyclophotocoagulation techniques: continuous wave versus micropulse for glaucoma treatment

Author: Johansyah CAP, Bambang L.

Geographical coverage: Not reported

Sector: Glaucoma treatment

Sub-sector: Safety and efficacy

Equity focus: Not reported

Study population: Patients with glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Glaucoma is a major cause of irreversible blindness, affecting an estimated 80 million people worldwide by 2024, with numbers expected to reach 111.8 million by 2040. It silently damages the optic nerve until vision loss is permanent. Current treatments aim to reduce intra-ocular pressure (IOP)—the only modifiable risk factor—using medication, laser therapy or surgery. Cyclophotocoagulation (CPC) is a laser intervention that targets the ciliary body to reduce aqueous humour production and has traditionally been reserved for advanced disease because of a risk of inflammation and hypotony. More recently, micropulse cyclophotocoagulation (MP-CPC) has emerged as a safer, minimally invasive alternative. By delivering energy in brief pulses interspersed with cooling periods, MP-CPC allows thermal relaxation and limits collateral tissue damage. This review compares MP-CPC with the conventional continuous wave technique (CW-CPC) in terms of efficacy, safety, IOP reduction and complication rates, with the aim of assessing the potential of MP-CPC as a safer treatment for glaucoma.

Objectives:

To assess the efficacy and safety profile of MP-CPC compared with CW-CPC for the treatment of glaucoma.

Main findings:

Overall, MP-CPC demonstrated promising results, with comparable IOP reduction and a lower risk of severe complications than CW-CPC. The review included six studies published between 2015 and 2023: two randomised controlled trials (RCTs), three retrospective cohort studies and one prospective cohort study. Five studies reported a significant IOP reduction after both procedures, with similar success rates. One study, however, reported an increase in IOP after MP-CPC. Definitions of success varied, most commonly requiring at least a 20–30 % reduction in IOP or maintenance within a specified range. Some studies favoured MP-CPC for better outcomes, whereas others found CW-CPC more effective at maintaining stable IOP over time.

Five studies reported a reduction in the number of antiglaucoma medications required after treatment in both groups; one study reported an increase in medication use in both groups.

With respect to complications, MP-CPC generally exhibited a more favourable safety profile. Two studies found significantly lower complication rates with MP-CPC. Reported adverse events included anterior chamber inflammation, hypotony and, in severe cases, phthisis bulbi. Phthisis bulbi was observed only after CW-CPC in one study. Not all studies found statistically significant differences in complication rates.

Methodology:

The authors searched PubMed, ScienceDirect and the Cochrane Library for English-language studies published between 2015 and 2023 that compared MP-CPC with CW-CPC. Two reviewers independently screened records and resolved disagreements through discussion. Studies were graded using the Oxford Centre for Evidence-Based Medicine levels of evidence. Key outcomes extracted were IOP reduction, success rate, change in medication burden and complications.

Applicability/external validity:

Small sample sizes limited the generalisability of the findings. Most included studies were retrospective or cohort designs rather than RCTs, introducing a potential selection bias. Lack of standardisation of laser parameters for MP-CPC and inconsistent definitions of treatment success further reduced comparability. Although MP-CPC showed favourable safety and comparable efficacy, evidence in paediatric patients and those with neovascular glaucoma (NVG) remains scarce. Well-designed RCTs are required to establish optimal laser parameters and to validate the effectiveness of MP-CPC across glaucoma subtypes and patient populations.

Geographic focus:

The geographic origin of the included studies was not reported.

Summary of quality assessment:

We have medium confidence in the review’s conclusions. The search was limited to English-language publications and the authors did not search reference lists or contact experts for additional data. The quality of individual studies was not described in detail, no list of excluded studies was provided and results were not stratified by risk of bias. These limitations reduce certainty in the findings.