Deconstructing Anterior Segment Crowding: Preoperative Anatomical Predictors of Malignant Glaucoma After Primary Angle-Closure Glaucoma Surgery.

Understanding anterior segment crowding is essential for identifying preoperative risk factors for malignant glaucoma (MG) following phacoemulsification, intraocular lens implantation, and goniosynechialysis (PEI‒GSL) in primary angle-closure glaucoma (PACG). This retrospective case-control study compared 24 PACG patients who developed postoperative MG (MG group) to 24 randomly selected controls (control group). Preoperative ultrasound biomicroscopy (UBM) metrics included anterior chamber depth (ACD), lens vault (LV), ciliary process distance (CCD), ciliary body thickness, anterior ciliary body placement, trabecular‒ciliary process angle (TCPA), and simulated cilio-lenticular distance (sCLD). To eliminate observer bias, all exported raw UBM images were completely anonymized, stripped of all identifiable metadata, randomized, and assigned unique computer-generated hashes before undergoing single-blinded evaluation. The MG group exhibited significantly shorter sCLD, greater LV, shallower ACD, and narrower TCPA preoperatively, with standardized mean differences exceeding 0.8. After False Discovery Rate correction, these differences remained significant (adjusted P < 0.05). Crucially, multivariable logistic regression adjusting for axial length (AL) demonstrated that a shortened sCLD (P < 0.001), an increased LV (P < 0.001), and a narrowed TCPA (adjusted P = 0.0099) maintained highly robust independent associations with MG development. The MG group showed a trend of weakened parameter coordination, particularly between AL and ACD (r = 0.334 vs. 0.718). Exploratory principal component analysis identified an architectural "anterior segment crowding" axis (explaining 62.2% of the variance), with the MG group clustering negatively. An exploratory, unweighted composite ciliary block score showed a large separation effect size (Cohen's d = 1.995, P < 0.001). In conclusion, preoperative shortened sCLD, increased LV, and narrowed TCPA constitute an anatomical risk cluster independently associated with postoperative MG. While anterior segment crowding characterizes this cohort, these multivariate models function strictly as exploratory, sample-specific constructs and explicitly lack external clinical validation.