Effect of laser peripheral iridotomy in subgroups of primary angle closure based on iris insertion

Abstract

Purpose: To investigate the effect of laser peripheral iridotomy (LPI) in subgroups of primary angle closure (PAC or PAC glaucoma) eyes based on iris insertion using anterior segment optical coherence tomography (AS-OCT)-derived parameters.

Methods: AS-OCT images of the anterior chamber were obtained before and 2 weeks after LPI in angle closure(PAC or PAC glaucoma) eyes. Qualitative classification of angle closure eyes according to iris insertion into ciliary body (basal insertion group (BIG) and apical insertion group(AIG)) were performed using AS-OCT images obtained before LPI. Anterior chamber depth (ACD), lens vault (LV), iris curvature (IC), iris area (IA), iris thickness (IT⁷⁵⁰) and angle opening distance (AOD⁷⁵⁰) 750 micron from scleral spur were calculated from AS-OCT images. AS-OCT parameters were compared before and after LPI treatment to evaluate whether the outcome of LPI differs between BIG and AIG. Uni- and multivariate logistic regression analysis was carried out to evaluate factors associated with AOD⁷⁵⁰ before and after LPI in each subgroup.

Results: Ninety-two PAC or PACG subjects were imaged and categorized into AIG (43 eyes) and BIG (89 eyes), respectively. AIG was significantly older (62.6 ±5.7 and 59.8± 7.3 years, p=0.043), and more hyperopic (1.44 ± 1.13 and 0.89 ± 1.11 D, p=0.021). Mean change after LPI was not significantly different between AIG and BIG in all AS-OCT parameters. In AIG, AOD⁷⁵⁰ was affected by ACD (p<0.001) and IA(p=0.05) before LPI, and LV (p=0.012) after LPI. In BIG, LV (p=0.007) before LPI, and ACD (p<0.001), IT⁷⁵⁰ (p=0.039) after LPI.

Conclusions: The outcome of LPI was not significantly different between angle closure subgroups with different iris insertion. However, anatomical factors affecting AOD⁷⁵⁰ showed difference between two groups, both before and after LPI.