Title:
Acute angle closure: qualitative and quantitative evaluation of the anterior segment using anterior segment optical coherence tomography.

Abstract:
To evaluate different mechanisms of acute angle closure and to compare it with unaffected fellow eyes and primary angle closure suspects using anterior segment optical coherence tomography.
Prospective, cross-sectional.
116 eyes (76 patients) with angle closure disease were included.
Eyes were categorized into three groups: (i) acute angle closure (40 eyes); (ii) fellow eyes of acute angle closure (40 eyes); and (iii) primary angle closure suspect (36 eyes). Complete ophthalmic examinations including gonioscopy, A-scan biometry and anterior segment optical coherence tomography were performed.
Based on the anterior segment optical coherence tomography images, four mechanisms of primary angle closure including pupil block, plateau iris configuration, thick peripheral iris roll and exaggerated lens vault were evaluated among the three subtypes of angle closure disease.
There was a statistically significant difference in the mechanism of angle closure disease among the three groups (P < 0.001). Although the majority of fellow and primary angle closure suspect eyes had pupil block mechanism (77.5% and 75%, respectively), only 37.5% of acute angle closure eyes had dominant pupil block mechanism. The percentage because of exaggerated lens vault was greatest in acute angle closure eyes (50%). Acute angle closure eyes had the shallowest anterior chamber depth (P < 0.001), least iris curvature (P < 0.001) and greatest lens vault (P = 0.003) compared with the other two groups.
A statistically significant difference in the underlying primary angle closure mechanisms among acute angle closure eyes as compared with their fellow eyes and primary angle closure suspect may exist.