Optimal Dimension of Peripheral Iridotomy for Anatomical Efficacy in Primary-Angle-Closure Disease

The aim of this study is to determine the optimal functional size of laser peripheral iridotomy (LPI) for anterior chamber parameter improvement in primary angle-closure disease (PACD). This study evaluated 109 eyes from 62 consecutive phakic patients. Baseline and one-week post-LPI anterior segment OCT were utilized to measure anterior chamber volume (ACV), anterior chamber angle (ACA), and iridotomy dimensions. Data was analyzed using linear mixed-effects models (LMMs), generalized additive models (GAMs), and receiver operating characteristic (ROC) curves. Post-LPI, significant increases occurred in ACA 500 (+7.54°), ACV (+11.09 mm³), and gonioscopic grade. LMMs confirmed a positive association between iridotomy size and anatomical expansion. GAMs demonstrated a saturation effect for ACV improvement, plateauing at 0.1 mm² (narrow area) and 0.25-0.30 mm² (superficial area), while the ACA relationship remained predominantly linear. ROC analysis identified preliminary superficial area cutoffs of 0.14 mm² and 0.12 mm² as discriminators of above-median volumetric and angular response, respectively. These findings suggest that LPI size is an independent determinant of anatomical response, beyond simple patency. As a preliminary, hypothesis-generating target, a superficial iridotomy area of approximately 0.12-0.14 mm² was associated with above-median volumetric and angular response in this cohort. Prospective validation is required before these thresholds can be incorporated into clinical practice.