Exploring iridotrabecular contact index and related factors in primary angle closure disease: a swept-source anterior segment OCT study

BACKGROUND/AIMS: This study evaluates the relationship between the iridotrabecular contact (ITC) index and various anterior segment parameters, with a particular focus on lens-related parameters, given their clinical relevance in primary angle closure disease (PACD). METHODS: A retrospective analysis was conducted on consecutive patients with PACD who underwent swept-source anterior segment optical coherence tomography (AS-OCT). All AS-OCT images were manually reviewed. Relative lens vault greater than one-third was defined as 'high vault'." The ability to detect an ITC index ≥50% was assessed using area under the receiver operating characteristic curve (AUROC). Decision tree analysis identified factors influencing the ITC index. RESULTS: A total of 376 patients were initially identified, and after applying exclusion criteria, 119 eyes of 119 PACD patients were included in the final analysis. The mean ITC index was 50.2%±30.5%, with a mean relative lens vault of 0.31±0.10. High vault was significantly associated with higher ITC index (p<0.001), and a positive correlation was observed (r=0.451, p<0.001). The angle recess area at 500 µm (ARA 500) parameter had the highest AUROC (0.983) for detecting ITC index ≥50%. Decision tree analysis identified trabecular iris space area at 500 µm and ARA 500 as key factors, but adding relative lens vault did not improve differentiation. CONCLUSIONS: A significant correlation exists between relative lens vault and the ITC index in PACD. However, lens vault does not enhance the diagnostic accuracy of angle parameters for identifying the ITC index. Comprehensive evaluation of PACD should include parameters beyond lens measurements.