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Abstract

Purpose Multiple modalities have been used to image the anterior chamber angle. We quantified changes in novel parameters associated with angle closure, namely anterior chamber area (ACA) and volume (ACV); anterior chamber width (ACW); lens vault (LV) and iris thickness, area and curvature using ASOCT, in a cohort of primary angle closure suspects (PACS) after laser peripheral iridotomy (LPI).

Methods A prospective study of primary angle closure suspects > 50 years of age after LPI. ASOCT images (Visante, Carl Zeiss Meditec, Dublin, CA) from 176 subjects were analyzed quantitatively using customized software, before and 1 week after LPI.

Results The mean age of the 176 participants was 63.0 ± 7.3 year and majority of the subjects were Chinese (95.5%) and women (76.7%). After LPI, the angle width opened significantly with increase in mean angle opening distance [AOD 500, 0.11 vs. 0.18 mm, p< 0.001), trabecular iris surface area (TISA500, 0.06 vs. 0.08 mm², p< 0.001) and angle recess area (ARA, 0.12 vs. 0.17 mm², p< 0.001). Mean ACA (14.9 vs. 16.0 mm², p< 0.001) and ACV (91.6 vs. 103.0 mm³, p< 0.001) increased significantly after LPI, but there was no change in ACW (11.21 vs. 11.24 mm, p = 0.3), anterior chamber depth (2.16 vs. 2.17 mm, p = 0.16) or LV (783.6 vs. 788.6µm, p = 0.72). Mean iris curvature was reduced (0.375 vs. 0.180 mm, p< 0.001) after LPI, but there was no significant change in iris thickness or area.

Conclusion LPI results in a significant increase in the angle width in subjects with narrow angles. ACA and ACV increased after LPI but there was no change in ACD, ACW, LV or iris thickness and area. The increase in ACA/ACV is attributed to be due to decreased iris curvature after LPI.