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Response to Letter to the Editor: One-Year Outcomes of Micropulse Cyclophototherapy for Primary Open-angle Glaucoma

Tong, Weihan MBBCh, BAO*; Yu Ting Shen, Tina MBBS*; Wong, Hung Chew MSc; Aquino, Maria C. MMed*; Chew, Paul FRCSEd*; Lim, Dawn MRCP*

Author Information
doi: 10.1097/IJG.0000000000002041
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We thank Grippo and colleagues for their interest and comments regarding our study.

Our study found that micropulse transscleral cyclophototherapy (MPTCP) had a transient and modest effect in eyes with primary open-angle glaucoma, with a similar medication burden.1 We believe MPTCP remains to be a very useful treatment modality, especially for patients with concurrent medical comorbidities requiring optimization before definitive glaucoma surgery.1

First, Grippo and colleagues believed that our study’s treatment parameters were subtherapeutic, leading to a suboptimal effect of MPTCP. Many studies on MPTCP were conducted in different geographical areas and included patients with different ethnicities as well as different glaucoma subtypes.2,3 With these differences, direct comparison of outcomes between different studies, such as retreatment rates, should be avoided.

MPTCP utilizes diode laser energy which is absorbed by pigmented intraocular tissues, including that of the ciliary body epithelium.4 In our study, our patients are of ethnic races with more tissue pigmentation. Taking the above into account, our parameters seek to avoid excessive energy delivery to our patients’ eyes, in which the intraocular tissues are more likely to absorb more energy compared with patients of less pigmented races. Higher energy delivered may potentially play a contributory role to complications seen, such as inflammation, tonic pupil and cystoid macular edema.2,3

There is currently no consensus on a standardized protocol for MPTCP treatment parameters. Variations in the laser parameters used in the real world setting often depend on surgeon preferences and are adapted to the patients’ clinical characteristics for patient safety, which is paramount. As mentioned, MPTCP can always be safely repeated when required and its relative safety has been described in previous studies.1,4,5

Second, we had acknowledged that the retrospective nature of the study carry its inherent limitations.1 Treatment parameters varied between patients who were managed by different surgeons. Hence, specific information such as sweep velocity was not available. As mentioned in our article, we suggest for more prospective studies to examine the effects of various treatment parameters and their influence on the outcomes of intraocular pressure lowering in different glaucoma subtypes.1

We believe the above discussion addresses the points raised by Grippo and colleagues. In future, when more information is gathered from larger prospective studies, recommendations on MPTCP settings can be made for optimal patient care, taking into account specific patient demographics and glaucoma subtypes.

Weihan Tong, MBBCh, BAO*

Tina Yu Ting Shen, MBBS*

Hung Chew Wong, MSc†

Maria C. Aquino, MMed*

Paul Chew, FRCSEd*

Dawn Lim, MRCP*

*Department of Ophthalmology, National University Hospital Singapore

†Research Support Unit, National University Health System, National University of Singapore, Singapore Singapore


1. Tong W, Shen TYT, Wong HC, et al. One-year outcomes of micropulse cyclophototherapy for primary open-angle glaucoma. J Glaucoma. 2021;30:911–920.
2. Yelenskiy A, Gillette TB, Arosemena A, et al. Patient outcomes following micropulse transscleral cyclophotocoagulation: intermediate-term results. J Glaucoma. 2018;27:920–925.
3. Al Habash A, AlAhmadi AS. Outcome of MicroPulse(®) transscleral photocoagulation in different types of glaucoma. Clin Ophthalmol. 2019;13:2353–2360.
4. Tan AM, Chockalingam M, Aquino MC, et al. Micropulse transscleral diode laser cyclophotocoagulation in the treatment of refractory glaucoma. Clin Exp Ophthalmol. 2010;38:266–272.
5. Aquino MC, Barton K, Tan AM, et al. Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study. Clin Exp Ophthalmol. 2015;43:40–46.
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