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Nathan G. Congdon, Mingguang He, Paul Foster, Yuzhen Jiang, Jian Zhang, Xixi Yan, Tom van den Berg, David Friedman; Subjective And Objective Measures Of Glare After Laser Peripheral Iridectomy Randomized To One Eye: the ZAP Trial. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5020.
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To understand which aspects of the size and location of a laser peripheral iridotomy (LPI) are associated with objectively-measured straylight scatter and subjective glare.
A convenience sample of subjects from the ZAP trial, who had received LPI at random in one eye for narrow angles 18 months previously, underwent the following: vision assessment, photo-documentation of LPI with photogrammetry (vertical/horizontal diameter, circumference, area, clock hour, distance from limbus and pupil, covered/uncovered/partially covered by lid in primary and downward gaze), bilateral LOCS III cataract grading, and ocular straylight testing (C-Quant, Oculus, Inc., Lynnwood WA). Subjects were also asked about subjective glare using two questions from the NEI VFQOL questionnaire.
Among 134 subjects, mean age was 60.6 +/- 5.13 years, 80.6% were women, 61.9% had presenting VA ≥ 20/25, 20.1% had nuclear opalescence > 3.0, 16.4% had cortical cataract > 2.5, none had any PSC, 10.4% (n=14) reported subjective glare, and 10.4% (n=14) and 14.2% (n=19) had LPI partially and totally uncovered by the lid in primary gaze respectively. Straylight score in the treated and un-treated eyes did not differ for all subjects (P = 0.5) or for subjects with partially/totally un-covered LPI (P = 0.6). In univariate and multivariate analyses, only worse cortical cataract grade (P < 0.001), and not LPI size or location, was significantly associated with straylight score. Only older age (P = 0.03), and not any of the LPI size/ location parameters, was significantly associated with subjective glare in multivariate models.
The impact of even un-covered LPI on objective measures of straylight does not appear to be great compared to that of lens opacity. Initial results suggest that programs to screen and treat narrow angles may be unlikely to result in significant glare disability. Recruitment of subjects is on-going, and objective/subjective glare data for age- and gender-matched un-treated controls will be reported.
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