To evaluate the clinical characteristics and multimodal biometric parameters from ultrasound biomicroscopy (UBM) and IOL Master biometry of patients with acute secondary angle-closure due to lens subluxation (ASAC-LS), acute primary angle-closure (APAC), and cataract.This retrospective study included 22 eyes with ASAC-LS, 27 eyes with APAC, and 39 eyes with cataract. Gender, age, affected eye, best corrected visual acuity, axial length, central corneal thickness, and anterior chamber depth (ACD) assessed by UBM and IOL Master were measured and compared between the three groups. In addition, we compared the ratio of ACD (ACD ratio) and the difference of ACD (ACD difference) measured by the two instruments. Logistic regression analysis was conducted to evaluate the predictive factors for lens subluxation. Receiver operating characteristic (ROC) curves were plotted to obtain a suitable cutoff value of biometric parameters to separate ASAC-LS cases from APAC and cataract cases.In the ASAC-LS group, the median (interquartile range [IQR]) ACD measured by IOL Master was 2.47 (IQR 1.85-2.92) mm while the median ACD measured by UBM was 3.11 (IQR 2.60-3.76) mm. The difference of ACD measured by the two instruments was statistically significant in the ASAC-LS group (P < 0.001) whereas the differences were not statistically significant in the APAC group (P = 0.521) and cataract group (P = 0.204). Subsequent pairwise comparison revealed that only the ACD difference (0.40 [IQR 0.22-1.08] mm) and ACD ratio (1.18 [IQR 1.07-1.40]) in the ASAC-LS group were significantly different from those in the APAC group (ACD difference 0.02 [IQR 0.01-0.07] mm; ACD ratio 1.01 [IQR 1.00-1.04]) and cataract group (ACD difference 0.09 [IQR 0.01-0.14] mm; ACD ratio 1.03 [IQR 1.00-1.04]) (all P < 0.001). The ACD difference and ACD ratio were significantly associated with lens subluxation in the multivariate logistic regression analysis (P < 0.001 and P = 0.001, respectively). Additionally, the ROC curve analysis showed that the ACD difference at 0.235 mm and the ACD ratio at 1.080 were the respective cut-off values for lens subluxation, with a sensitivity of 77.3% and specificity of 100.0%.Our findings provide a new option for identifying lens subluxation. Specifically, combining the ACD from UBM and IOL Master may be helpful for differential diagnosis of ASAC-LS.© 2022. The Author(s).