Comparison of iridolenticular contact area under different light brightness between post primary acute angle closure and cataract eyes

Background To study the iridolenticular contact area (ILCA) under different light conditions in acute primary angle closure (APAC). Methods This cross-sectional, observational study involved 22 unilateral APAC patients and 59 cataract patients (59 eyes). Images of the APAC eyes, fellow eyes and cataract eyes were collected by anterior segment optical coherence tomography (ASOCT) under different light conditions respectively. The ILCA, anterior chamber width (ACW), anterior chamber area (ACA), lens vault (LV), angle opening distance at 750 μm (AOD750), trabecular iris space area at 750 μm (TISA750) and iris area at 750 μm (IA750) were measured using Image J software. Results The ILCA of cataract eyes were significantly larger than APAC eyes (4.424 ± 1.208 vs 4.049 ± 2.725mm 2 , P = 0.034) and fellow eyes (4.424 ± 1.208 vs 3.651 ± 1.629 mm 2 , P = 0.008) under dark condition. Under dark condition, ILCA of APAC eyes was negatively correlated with AOD750 ( r = -0.444, P = 0.038), TISA750 ( r = -0.498, P = 0.018). The ILCA of cataract eyes under dark condition was significantly greater than under bright condition (4.424 ± 1.208 vs 2.526 ± 0.992 mm 2 , P < 0.001). Conclusions This study showed that ILCA in both APAC eye and fellow eye were smaller than cataract eye. Future study should focus on both the contact area and force at the interface of lens and iris with larger sample size.