Classification of primary angle closure spectrum with hierarchical cluster analysis

Abstract

PurposeTo classify subjects with primary angle closure into clusters based on features from anterior segment optical coherence tomography (ASOCT) imaging and to explore how these clusters correspond to disease subtypes, including primary angle closure suspect (PACS), primary angle closure glaucoma(PACG), acute primary angle closure (APAC) and fellow eyes of APAC and reveal the factors that become more predominant in each subtype of angle closure.MethodA cross-sectional study of 248 eyes of 198 subjects(88 PACS eyes, 53 PACG eyes, 54 APAC eyes and 53 fellow eyes of APAC) that underwent complete examination including gonioscopy, A-scan biometry, and ASOCT. An agglomerative hierarchical clustering method was used to classify eyes based on ASOCT parameters.ResultsStatistical clustering analysis produced three clusters among which the anterior segment parameters were significantly different. Cluster 1(43 eyes) had the smallest anterior chamber depth(ACD) and area, as well as the greatest lens vault (p<0.001 for all). Cluster 2(113 eyes) had the thickest iris at 2000 microns(p = 0.048), and largest iris area(p<0.001), and the deepest ACD (p<0.001). Cluster 3(92 eyes) was characterized by elements of both clusters 1 and 2 and a higher iris curvature(p<0.001). There was a statistically significant difference in the distribution of clusters among subtypes of angle closure eyes(p<0.001). Although the patterns of clusters were similar in PACS and PACG eyes, with the majority of the eyes classified into cluster 2(55%, and 62%, respectively), the highest proportion of APAC and fellow eyes were assigned to clusters 1(44%) and 3 (51%), respectively.ConclusionHierarchical cluster analysis identified three clusters with different features. Predominant anatomical components are different among subtypes of primary angle closure.

Establishment and Comparison of Algorithms for Detection of Primary Angle Closure Suspect Based on Static and Dynamic Anterior Segment Parameters

“…40 Cluster 1 had the smallest ACD and ACA, as well as the largest LV, suggesting a pushing mechanism as a result of the forward movement of the lens and increased LT. 40 Cluster 2 had the largest IT at 2000 μ, largest IA, and deepest ACD, which may result in angle crowding and subsequent angle closure due to a predominant iris component. 40 Cluster 3 was characterized by elements of both clusters 1 and 2 and a higher iris curvature suggesting a predominant PB mechanism. 40 We further categorized the enrolled 405 PACS eyes into different subgroups based on the main angle closure mechanisms.…”

“…Moghimi et al also reported three different angle closure subtypes among PACS, PACG, acute primary angle closure, and the fellow eyes of acute primary angle closure using statistical clustering analysis based on ASOCT parameters. 40 Cluster 1 had the smallest ACD and ACA, as well as the largest LV, suggesting a pushing mechanism as a result of the forward movement of the lens and increased LT. 40 Cluster 2 had the largest IT at 2000 µ, largest IA, and deepest ACD, which may result in angle crowding and subsequent angle closure due to a predominant iris component. 40 Cluster 3 was characterized by elements of both clusters 1 and 2 and a higher iris curvature suggesting a predominant PB mechanism.…”

“…40 Cluster 3 was characterized by elements of both clusters 1 and 2 and a higher iris curvature suggesting a predominant PB mechanism. 40 We further categorized the enrolled 405 PACS eyes into different subgroups based on the main angle closure mechanisms. 129 eyes were found to have PB (33.3%), 138 eyes PIC (35.7%), and 120 eyes TPIR (31.0%) as the dominant angle closure mechanism.…”

“… 40 Cluster 3 was characterized by elements of both clusters 1 and 2 and a higher iris curvature suggesting a predominant PB mechanism. 40 …”

Trends in the characteristics of acute primary angle closure in Korea over the past 10-years

“…Patients with APAC had to satisfy all four of the following criteria to be included in the study. (a) at least two of the symptoms of an acute IOP elevation: ocular or peri-ocular pain, nausea and/or vomiting, halos; (b) clinical signs: conjunctival injection, microcytic corneal edema, mid-dilated pupil, and shallow AC; (c) IOP at presentation of at least 30 mmHg; (d) presence of occludable angle, confirmed by gonioscopy [17]. Occludable angle closure was defined if the posterior trabecular meshwork (TM) could not be visualized in at least 3 quadrants.…”