Anatomic Predictors for Anterior Chamber Angle Opening After Laser Peripheral Iridotomy in Narrow Angle Eyes

Abstract

Purpose: To investigate anterior chamber parameters and biometric factors associated with degree of angle opening after laser peripheral iridotomy (LPI) for narrow angles.

Methods: In this prospective cohort study, patients with narrow angles who were scheduled for LPI were recruited. Anterior chamber parameters by anterior segment coherence tomography (ASOCT) under dark conditions were compared before and after LPI. Only the right eye was used for analysis if both eyes were eligible. Measurements performed by customized software included anterior chamber depth, iris area, angle opening distance at 500 µm (AOD500) anterior to the scleral spur, iris thickness at 750 µm from sclera spur (IT750), trabecular-iris space area 500 (TISA500), and iris curvature (I-Curv). Univariate and multiple regression analyses were performed to determine the predictive factors of angle opening after LPI.

Results: Eighty-one patients with narrow angles were prospectively recruited in this study. The AOD500 increased significantly from 0.128 ± 0.081 mm (before) to 0.209 ± 0.087 mm (after) in the nasal quadrant, and from 0.103 ± 0.067 mm (before) to 0.197 ± 0.071 mm (after) in the temporal quadrant (p < 0.001 for both nasal and temporal). I-Curv decreased significantly after LPI (p < 0.001). Significant increase was noted in TISA500 before and after LPI (p < 0.001). In the multiple regression model, increase in AOD500 was positively correlated with age (standardized β = 0.283, p = 0.007) and I-Curv (standardized β = 0.239, p = 0.021), and was negatively correlated with preoperative iris area (standardized β = −0.292, p = 0.015).

Conclusions: In this hospital-based study on the results of LPI for narrow angle subjects, statistically significant independent predictors of anterior chamber angle widening after LPI were older age, smaller iris area, and steeper iris.

Keywords::

• ASOCT
• LPI
• Narrow angle
• Angle opening distance
• Iris parameter

ACKNOWLEDGMENTS

The authors thank the contribution of Dandan Wang for her graphic representing a schematic of ZAAP software in the paper. The authors thank the contribution of Jian Zhang for his statistical instruction in the paper. This study was supported by core grant EY002162 from the National Eye Institute; That Man May See, Inc; and Research to Prevent Blindness.

Declaration of interest: The authors reports no conflicts of interest. The authors alone are responsible for the content and writing of the paper.