Peripheral iris thickness and association with iridotrabecular contact after laser peripheral iridotomy in patients with primary angle-closure and primary angle-closure glaucoma

Abstract

Takanori Mizoguchi,1 Mineo Ozaki,2,3 Harumi Wakiyama,1,4 Nobuchika Ogino1,5 1Mizoguchi Eye Clinic, Sasebo, Japan; 2Ozaki Eye Clinic, Miyazaki, Japan; 3Department of Ophthalmology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan; 4Japanese Red Cross Nagasaki Genbaku Hospital, Nagasaki, Japan; 5Nishigaki Eye Clinic, Nagoya, Japan Purpose: To investigate the relation between the quantitative iris parameters and iridotrabecular contact (ITC) in patients with primary angle-closure (PAC) and PAC glaucoma (PACG). Materials and methods: PAC and PACG with laser peripheral iridotomy were recruited prospectively. Anterior-segment optical coherence tomography (ASOCT) was performed under light and dark conditions, and scans were taken along the vertical and horizontal axes. Iris thickness at 500 µm (IT500) and 750 µm (IT750) from the scleral spur, maximal iris thickness (MIT), and cross sections of the iris area (I-Area) were measured by using software. ITC was defined by the ASOCT as the contact between the peripheral iris and angle wall anterior to the scleral spur. The ITC+ and ITC- groups were defined as eyes that had ITC in two or more quadrants and in no or one quadrant, respectively. Results: A total of 79 eyes of 60 patients (consisting of 48 PAC and 31 PACG) were recruited. The prevalence of superior, inferior, temporal, and nasal ITC was 44 eyes (55.7%), 48 eyes (60.8%), 18 eyes (22.8%), and 16 eyes (20.2%), respectively. These iris parameters of the inferior quadrant, which had the highest prevalence of all the quadrants, were used for the analysis. After adjusting for age, sex, pupil size, and central anterior chamber depth, mean values of IT500 and IT750 were significantly greater in the ITC+ group than the ITC- group (P<0.05). Multivariate-adjusted odds ratios of parameters for the ITC+ group compared with the ITC- group were: IT500, 1.9 (P=0.029); IT750, 2.0 (P=0.011), MIT, 1.4 (P=0.244), and I-Area, 0.97 (P=0.406), respectively, per 0.1-unit increase. Conclusion: Peripheral iris thickness is associated with ITC in patients with angle closure. Keywords: angle-closure glaucoma, iridotrabecular contact, anterior-segment optical coherence tomography, iris thickness, iris area