Ocular Biometric Parameters of Acute Primary Angle Closure with Varying Degrees of Lens Zonular Laxity

Acute primary angle closure (APAC) is a leading cause of irreversible blindness. Recent studies suggest lens zonular laxity plays a critical role in APAC pathogenesis, though its clinical detection remains challenging due to overlapping symptoms with cataract. This study investigates the prevalence of subclinical zonular degeneration in APAC patients and its correlation with ocular biometric parameters.

This retrospective cohort study included 65 APAC patients (mean age 62.3 ± 8.7 years) undergoing phacoemulsification at Zibo Central Hospital (November 2021-May 2023). Patients were stratified into three groups based on intraoperative zonular status: normal zonula (APAC-NZ, n=14), mild zonular laxity (APAC-ZL, n=39), and significant zonular laxity (APAC-SZL, n=12). Preoperative axial length (AL), lens thickness (LT), and anterior chamber depth (ACD) were measured using IOLMaster 5.0 and swept-source UBM.

A high prevalence (78.5%, 51/65) of undiagnosed zonular degeneration was observed. Significant differences were found in sitting ACD (2.25 ± 0.17 mm vs 1.75 ± 0.19 mm), supine ACD (1.72 ± 0.11 mm vs 1.27 ± 0.12 mm), and LT (5.10 ± 0.28 mm vs 5.41 ± 0.38 mm) between APAC-NZ and APAC-SZL groups (P<0.05). Similar differences were noted between APAC-SZL and APAC-ZL groups (P<0.05).

This study introduces a novel stratification of APAC patients by zonular laxity severity and reveals distinct biometric profiles across subgroups. We demonstrate a high prevalence of undiagnosed zonulopathy in APAC patients, associated with thicker lenses and shallower anterior chambers. A key limitation is the subjective classification of zonular laxity, based solely on intraoperative observations. Future studies should develop objective imaging protocols for improved detection and management.