Analysis of ocular biometric parameters in patients with primary angle closure diseases at different refractive status

It is well known that shallow anterior chamber depth (ACD), thick lens, and short axial length (AL) are recognized as biometric characteristics for primary angle closure glaucoma (PACG).1–5 Usually, inmyopic eyes, ACD became deeper, anterior chamber volumes became larger and AL became longer, suggesting that the chance for these eyes to develop PACG is lower than that in hyperopic eyes at least in theory.6 However, Yong et al. reported that 94 (22%) of 427 angle closure subjects had myopia, while 11 (2.6%) were high myopia (≤ −5.0 diopter (D)).7 The underlying mechanisms of PACG accompanied by myopia remain unclear. To explore the etiology of angle closure eyes with myopia, our study retrospectively analyzed the ocular biometric parameters in patients with primary angle closure diseases (PACD) at different refractive status. This is a multicenter and cross-sectional study involving four eye centers aroundChina, which collected 1014 eyeswith PACD from January 2019 to August 2021. This retrospective study was approved by the Medical Research and Ethics Committee and corresponded to the Declaration of Helsinki. The different types of PACD are defined as PACS, APACG, and CPACG.8–10 Refractive status was derived from the spherical equivalent (SE; sphere + 1/2 cylinder). According to the refractive status, the eyes were divided into three groups: (1) hyperopia group: SE ≥ +1.00 diopter (D), (2) myopia group: SE ≤ −1.00 D, and (3) emmetropia group: −0.50 D ≤ SE ≤ +0.50 D. The details of the methodology are provided in Supplementary methods. Central ACD, lens thickness (LT), AL, corneal curvature K1 and K2 were measured using the IOL Master® 700 (Zeiss, Germany). Vitreous length (VL) was calculated using the following formula: VL = AL − ACD − LT; and relative lens position (RLP) was calculated as RLP = (ACD + 0.5 LT)/AL.11 The continuous parametric characteristics were compared using one-way ANOVA analysis and the least significant difference (LSD) test. Categorical variables were compared using the chi-square test or Fisher’s exact test. The angle closure combined with myopia (ACCM) scoring system was established for evaluating ACCM risk. For assessing discriminative performance of the angle closure combined with myopia (ACCM) score, receiver operating characteristic (ROC) curve metrics was calculated. A two-tailed p < 0.05 was considered significant for all tests. Statistical analyses were performed using SPSS version 26.0 (IBM Corp, Armonk, NY, USA), and R software 3.6.3 (Vienna, Austria).