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Editors Selection IGR 24-3

Surgical Treatment: post-op aqueous misdirection afer PACG surgery

Comment by Sasan Moghimi on:

109732 Incidence and characteristics of aqueous misdirection after glaucoma surgery in Chinese patients with primary angle-closure glaucoma, Lin H; Li J; Zheng X et al., Eye and vision (London, England), 2023; 10: 28

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Primary angle-closure glaucoma (PACG) accounts for nearly half of all glaucoma related blindness, especially in Asia. Trabeculectomy, a mainstay of glaucoma treatment for decades, has been shown to have reliable long-term results in managing IOP. However, any aqueous-draining procedure in an eye with a shallow anterior chamber and a chronic closed angle has the potential for postoperative complications, most importantly aqueous misdirection. In recent years, a series of studies has highlighted the effectiveness of phacoemulsification with or without gonio-synechialysis in treating PACG,^1,2 and therefore surgical management has gradually shifted toward lens extraction in these eyes.³

Lin et al. in a retrospective study looked at the data of 5044 angle closure eyes who received glaucoma surgeries or cataract extraction between 2012 and 2021 and reported the incidence and clinical characteristics of aqueous misdirection in Chinese eyes. Thirty-eight eyes (0.75%) developed aqueous misdirection with the mean time interval between surgery and first record being 2.57 ± 5.24 months (range, 0 day to 24 months).

This incidence (0.75%) of aqueous misdirection was lower than that reported in most previous studies (2-4%).^4,5 A high rate of phacoemulsification with or without glaucoma procedures (78.01%), may explain the lower incidence of aqueous misdirection in their cohort. In fact, the incidence of aqueous misdirection for patients with PACG undergoing filtering surgery (2.27%) was much higher compared to those undergoing non-filtering surgery (0.37%).

Consistent with earlier findings, the occurrence of aqueous misdirection was 51 times higher in patients aged ≤ 40 years and eight times higher in those aged 40-50 years, as compared to individuals over the age of 50. This could be attributed to distinct anatomical characteristics of PACG in younger patients.

Interestingly, aqueous misdirection developed much less frequently among patients with acute angle-closure glaucoma (0.32%), compared to those with chronic angle-closure glaucoma (1.30%, P < 0.001). They did not provide information on the disparity in the rate of phacoemulsification between the two conditions, which could potentially account the difference in the incidence of aqueous misdirection.

While the strengths of this study include its large sample size and incorporating recent trends in management of angle closure, the results of the study should be interpreted by some limitations. The study is retrospective and suffers from a lack of completeness and accuracy of data. More importantly, intraocular pressure (IOP) of > 21mmHg was part of the definition for aqueous misdirection in their study. Since aqueous misdirection can present with normal or even low IOP, inclusion of aqueous misdirection with an elevated IOP before medical therapy means that they may underestimate the incidence of aqueous misdirection and the reported incidence may reflect the incidence of more severe cases of the condition. In fact, the mean IOP at onset of aqueous misdirection was 39.1 mmHg. This justifies why only 13% of their patients responded to medical therapy (compared to 50% in literature).

The results of the present study suggest that the incidence of aqueous misdirection after glaucoma surgery is lower than previously reported. This is likely attributed to recent trends in management of angle closures and reduced risk of this complication after lens extraction. Precautionary measures and timely assessment of aqueous misdirection should be implemented in young PACG patients who are undergoing filtering surgery.

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