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Editors Selection IGR 21-4

Surgical Treatment: Do Preoperative Glaucoma Medications affect Surgical Outcomes?

Comment by Ronald Fellman & Davinder S. Grover on:

112864 Impact of glaucoma medications on subsequent Schlemm's canal surgery outcome: Cox proportional hazard model and propensity score-matched analysis, Okuda-Arai M; Mori S; Takano F et al., Acta Ophthalmologica, 2023; 0:

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We applaud the authors on their continued focus on angle surgery and the use of anti-glaucoma medications (AGM). In a preceding publication, the authors found a longer duration of glaucoma drug use was associated with the surgical failure of microhook trabeculotomy, as determined by both Cox proportional hazard and propensity score matching.¹ The authors point to a worsening of the outflow system from preservatives and a disuse atrophy of the collector channels as possible reasons.

In their current article, using similar statistical methods, the authors found preoperative glaucoma medications that do not directly involve the conventional outflow pathway (beta blockers, alpha agonists, CAI, prostaglandin analogues) may have a detrimental effect on subsequent canal-based MIGS outcomes. In their analysis, they found no adverse effect with Rho kinase inhibitors, which, as we know, directly target trabecular outflow. Thus, certain glaucoma medications, as well as their duration, may be detrimental to the outcome of canal-based MIGS, and the reasons for this remain speculative, but decreasing flow through the trabecular system may be detrimental to canal-based MIGS.

Understanding the basis for Cox analysis and propensity scoring can be quite hazardous to clinicians who are not biostatisticians. No longer do we simply evaluate postoperative IOP's, but quasi-randomized comparisons that adjust for confounding factors is the new normal. It is likely impossible that statistical modelling can completely allow accurate comparisons regarding disease state and risk factors between all patients. Analysis of the benefits and detriments of these statistical analyzes are beyond the scope of this review but should always be kept in mind.

It is up to the reader to interpret the results of each glaucoma study and make the best decision possible for their patients based on sound judgment.

AGMs are not without risk and their use may be associated with poorer outcomes in terms of angle surgery

Overall, the authors found that AGMs are not without risk and their use may be associated with poorer outcomes in terms of angle surgery. While further studies are needed to elucidate these relationships, Okuda-Arai et al. have done substantial work reporting outcomes that are strongly suggestive of these findings. Moreover, their investigation gives us more evidence to consider minimizing a glaucoma patient's dependence on drops through laser trabeculoplasty and angle-based glaucoma surgeries, perhaps prior to committing patients to a lifelong course of 4-5 AGM used several times a day. We look forward to more studies from this group, as well as from others around the world, to help guide our decision making of this complex disease.

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