Abstract
Purpose: :
To study anterior segment changes in patients with narrow angles, after laser peripheral iridotomy (LPI), using gonioscopy and anterior segment optical coherence tomography (AS-OCT).
Methods: :
AS-OCT (Visante OCT, Carl Zeiss Meditec, Dublin, CA) and gonioscopy results before and after LPI were retrospectively analyzed. LPI was performed in the superotemporal quadrants by an experienced glaucoma specialist. The angle opening distance at 500 microns anterior to the scleral spur (AOD500); trabecular-iris space area up to 750 microns from the scleral spur (TISA750); angle recess area (ARA); anterior chamber depth, area, and volume (ACD, ACA, ACV, respectively); iris thickness at 750 and 2000 microns from the scleral spur (IT750, IT2000) and iris area were measured using the Zhongshan Angle Assessment Program (ZAAP4, Zhongshan, China). Occludable angle status was assigned if the average gonioscopy grade among the four quadrants was less than 2 by the Shaffer grading system.
Results: :
There were 36 eyes of 26 patients in the study. There were 8 males (31%) and 18 females (69%). The mean age was 67.7 years and the ethnic distribution consisted of 8 Caucasians (31%), 13 Asians (50%), 4 African-Americans (15%) and 1 Hispanic (4%). After LPI, 13/36 eyes (36%) were still occludable. The eyes that remained occludable had almost statistically significantly lower average gonioscopy prior to laser, as compared to eyes that were no longer occludable after LPI (0.94±0.51 and 1.33±0.58 respectively, p=0.054). However, there were no significant differences among pre-laser AS-OCT parameters between the two groups. In both groups, angle parameters improved and ACA and ACV increased after LPI; however, there were no changes in iris parameters. ACD did not change in the occludable group but did increase in the non-occludable group (Table 1).
Conclusions: :
Although all angle parameters showed improvement after LPI, one-third of treated eyes remained classified as occludable. These eyes had narrower angles before laser than those which were non-occludable after LPI. Iris thicknesses and area did not change after LPI.
Keywords: anterior segment • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • laser