Longitudinal Changes of Angle Configuration in Primary Angle-Closure Suspects

Abstract

Objective-To determine longitudinal changes in angle configuration in the eyes of primary angle-closure suspects (PACS) treated by laser peripheral iridotomy (LPI) and in untreated fellow eyes. Design-Longitudinal cohort study.Participants-Primary angle-closure suspects aged 50 to 70 years were enrolled in a randomized, controlled clinical trial.Methods-Each participant was treated by LPI in 1 randomly selected eye, with the fellow eye serving as a control. Angle width was assessed in a masked fashion using gonioscopy and anterior segment optical coherence tomography (AS-OCT) before and at 2 weeks, 6 months, and 18 months after LPI. Main Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts distance (AOD250, AOD500, AOD750), trabecular-iris space area (TISA500, TISA750), and angle recess area (ARA) measured in AS-OCT images.Results-No significant difference was found in baseline measures of angle configuration between treated and untreated eyes. At 2 weeks after LPI, the drainage angle on gonioscopy widened from a mean of 13.5° at baseline to a mean of 25.7° in treated eyes, which was also confirmed by significant increases in all AS-OCT angle width measures (P<0.001 for all variables). Between 2 weeks and 18 months after LPI, a significant decrease in angle width was observed over time in treated eyes (P<0.001 for all variables), although the change over the first 5.5 months was not statistically significant for angle width measured under gonioscopy (P = 0.18), AOD250 (P = 0.167) and ARA (P = 0.83). In untreated eyes, angle width consistently decreased across all follow-up visits after LPI, with a more rapid longitudinal decrease compared with treated eyes (P values for all variables ≤0.003). The annual rate of change in angle width was equivalent to 1.2°/year (95% confidence interval [CI], 0.8-1.6) in treated eyes and 1.6°/year (95% CI, 1.3-2.0) in untreated eyes (P<0.001).Conclusions-Angle width of treated eyes increased markedly after LPI, remained stable for 6 months, and then decreased significantly by 18 months after LPI. Untreated eyes experienced a more consistent and rapid decrease in angle width over the same time period.Primary angle-closure glaucoma (PACG) predominantly presents in the form of a chronic asymptomatic condition 1-3 and is estimated to be responsible for approximately half of binocular glaucoma blindness worldwide. 4 A previous population-based study reported that more than 10% of elderly Chinese are asymptomatic suspects at risk of angle-closure. 5

Baseline Anterior Segment Parameters Associated with the Long-term Outcome of Laser Peripheral Iridotomy

“…In fact, aging substantially affects AS parameters, with increased LV, decreased ACD, and increased IC noted with age. 27,33 In previous studies, parameters such as AOD, LV, and IT 750 were substantially different when measured at 2 weeks and at 18 months post-LPI, 19,34 showing progressive change of AS features with time in PAC eyes underwent LPI.However, when we assessed the baseline factors which may predict the long-term outcome of LPI, greater AOD 750 and thicker IT were consistently associated with poor outcome. Recently, Han et al investigated the effect of LPI in subgroups of angle closure eyes based on AS OCTderived parameters and showed proportional change in AOD 750 after LPI was significantly greater in eyes with less AOD 750 at baseline, which supported the outcome of current study.…”

Effect of Laser Peripheral Iridotomy on Anterior Chamber Angle Anatomy in Primary Angle Closure Spectrum Eyes

“…Other studies have demonstrated progressive narrowing in patients who have had LPI with extended follow-up. 12, 23 Although statistically significant deepening did occur with LPI over the course of this study, the threshold of clinically significant angle deepening is unknown.…”

“…Previous studies have evaluated the changes in anterior chamber angle anatomy after LPI using gonioscopy, 8 ultrasound biomicroscopy (UBM), 9, 10 and time domain anterior segment optical coherence tomography (TD-ASOCT; Visante, Carl Zeiss Meditec, Inc., Dublin, CA). 11, 12 Clinically, gonioscopy can be used to visualize the angle structures qualitatively, but it is a challenging exam. Quantifying angle measurements or changes in those measurements is unreliable.…”

Is prophylactic laser peripheral iridotomy for primary angle closure suspects a risk factor for cataract progression? The Chennai Eye Disease Incidence Study

“…In the initial report on the natural history of PACS, angle width of treated eyes increased following LPI and remained stable for 6 months, then showed significant decrease in 18 months. At the present point of time LPI has not shown any great advantage over observation for PACS 19. The Asia Pacific Guidelines for glaucoma do not recommend LPI for all PACS mainly because the natural history of PACS is not well known 20.…”