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Editors Selection IGR 21-4

Anatomical Structures: How do Anterior Segment Changes affect the Chamebr Angle?

Comment by Kendra Hong & Benjamin Xu on:

112355 Progressive Changes in the Anterior Segment and Their Impact on the Anterior Chamber Angle in Primary Angle Closure Disease, Kwak J; Shon K; Lee Y et al., American Journal of Ophthalmology, 2024; 257: 57-65

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While eyes with primary angle closure disease (PACD) may initially exhibit widening of the anterior chamber angle (ACA) after laser peripheral iridotomy (LPI), the Zhongshan Angle Closure Prevention (ZAP) Trial demonstrated that the ACA tends to narrow again by 18 months after LPI.¹ In this longitudinal study, Kwak and colleagues² used AS-OCT to investigate progressive age-related anatomical changes in PACD eyes over a longer period of time after LPI. 103 Korean patients with PACD underwent LPI and were followed for a mean of 6.5 years. While ACA parameters appeared to narrow gradually after the initial angle-widening effect of LPI, narrowing of angle opening distance at 750 μm (AOD750) did not maintain statistical significance. In contrast, lens vault (LV) significantly increased with time, which was associated with significant decreases in AOD750, angle recess area at 750 μm (ARA750), and iris thickness at 750 μm. The authors hypothesized that while the development of age-related cataracts increased LV and narrowed the ACA, aging was also associated with pupillary constriction and peripheral iris thinning, which offset angle-narrowing effects of cataractogenesis.

These findings demonstrate that chronic anatomical changes of the anterior segment after LPI are complex and multi-factorial. The effect of LV on ACA parameters may have been underestimated since patients with rapid LV increases likely underwent lens extraction and were excluded from the study. Furthermore, while AOD750 did not narrow significantly after LPI, ARA750 did. Therefore, not all aspects of ACA narrowing were offset by age-related iris changes. Despite these limitations, this study offers valuable information about age-related anatomical changes after LPI. Both untreated and post-LPI PACS eyes with worrisome biometric trajectories may benefit from serial monitoring with AS-OCT so that treatment can be escalated as needed. However, additional research is needed to elucidate how longitudinal changes in the lens, iris, and ACA contribute to PACD progression.

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