Anterior segment imaging-based subdivision of subjects with primary angle-closure glaucoma

Abstract

PurposeThe purpose of this study was to identify whether it was possible to subdivide subjects with primary angle-closure glaucoma (PACG) based on anterior segment optical coherence tomography (ASOCT) imaging, and to determine the characteristics of such subgroups.MethodsWe evaluated 210 subjects with PACG. All subjects underwent gonioscopy and ASOCT imaging. Customized software was used to measure ASOCT parameters. An agglomerative hierarchical clustering method was first used to determine the optimum number of parameters to be included in the determination of subgroups. Then, the best number of subgroups was determined using Akaike Information Criterion (AIC) and Gaussian Mixture Model (GMM) methods.ResultsThe mean age of the subjects was 67.9 years, and 53.3% were female. Following the hierarchical clustering, four parameters (iris area, anterior chamber depth (ACD), anterior chamber width (ACW), and lens vault (LV)) were chosen to be representative of related parameters. The optimal number of subgroups using GMM analysis and AIC was 3. Subgroup 1 (N=89; 42.4%) was characterized by a large iris area, subgroup 2 (N=24; 11.4%) by a large LV and a shallow ACD, whereas subgroup 3 (N=97; 46.2%) displayed only intermediate values across iris area, LV, and ACD.ConclusionsWe identified three distinct subgroups of PACG subjects based on ASOCT imaging.

Plateau Iris Distribution Across Anterior Segment Optical Coherence Tomography Defined Subgroups of Subjects With Primary Angle Closure Glaucoma

“…5,6 We recently identified three distinct subgroups of PACG based on anterior segment optical coherence tomography (ASOCT) imaging and clustering analysis. 7 An ability to subcategorize angle closure based on the likely underlying mechanism rather than to lump all patients with angle closure into one group of eyes may lead to a better understanding of the condition and may help guide in individualized treatment of PACG subjects. Notably, in the ASOCT subgrouping analysis, 7 the ACD was significantly different among the three groups.…”

“…7 An ability to subcategorize angle closure based on the likely underlying mechanism rather than to lump all patients with angle closure into one group of eyes may lead to a better understanding of the condition and may help guide in individualized treatment of PACG subjects. Notably, in the ASOCT subgrouping analysis, 7 the ACD was significantly different among the three groups. Subgroup 1 was characterized by a larger iris area with deepest anterior chambers, subgroup 2 by a large lens vault (LV) and shallowest ACD, whereas subgroup 3 displayed intermediate values across iris area, LV, and ACD.…”

“…Subgroup 1 was characterized by a larger iris area with deepest anterior chambers, subgroup 2 by a large lens vault (LV) and shallowest ACD, whereas subgroup 3 displayed intermediate values across iris area, LV, and ACD. 7 Given the variable associations of plateau iris and ACD, we therefore aimed to assess the proportion of plateau iris across the three PACG subgroups. We hypothesize that the eyes categorized to subgroup 1, 7 characterized by significantly deeper ACD, would have the highest proportion of plateau iris, as plateau iris is conventionally defined to have a relatively deep central anterior chamber.…”

“…Details of the study have been described previously. 7 In brief, subjects aged 40 years and older and diagnosed with PACG were recruited from glaucoma clinics of the Singapore National Eye Centre. All subjects had previously undergone laser peripheral iridotomy (LPI) before recruitment into the study.…”

“…Details of the ASOCT grading has been described previously. 7 In brief ASOCT (Visante; Carl Zeiss Meditec) imaging was performed for all participants under standardized dark conditions (0 lux) by a single operator. The scans were centered on the pupil and a single cross-sectional horizontal image (nasal-temporal angles at 0-180 degrees) was obtained and evaluated for each subject.…”