Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

Background: To evaluate different mechanisms of primary angle closure and to quantify anterior chamber parameters in these mechanisms using anterior segment optical coherence tomography in an Asian population. Design: Hospital-based cross-sectional observational study. Participants: Forty-eight consecutive patients with primary angle closure glaucoma. Methods: Patients underwent complete ophthalmic examination and imaging of nasal-temporal angles with anterior segment optical coherence tomography. Images were categorized into four primary angle closure mechanisms: pupil block, plateau iris configuration, Thick peripheral iris roll and exaggerated lens vault. Parameters computed: anterior chamber depth central, anterior chamber depth at 1000 mu m and 2000 mu m anterior to scleral spur, lens vault, anterior chamber area, angle opening distance, trabecular iris space area and iris thickness. Main Outcome Measure: Anterior chamber parameters and primary angle closure mechanisms. Results: Mean values of anterior chamber depths: central (P < 0.001), at 2000 mu m (P < 0.001), 1000 mu m (P < 0.001), lens vault (P < 0.001), anterior chamber area (P < 0.001), were significantly different among the four groups. Multivariate analysis showed anterior chamber depths: central, and anterior chamber depth at 2000 mu m and anterior chamber area were higher in plateau iris and Thick peripheral iris roll and lower in exaggerated lens vault (P < 0.001) as compared to pupil block mechanism, lens vault was greater in exaggerated lens vault (P < 0.001) and lesser in plateau iris and Thick peripheral iris roll as compared to pupil block mechanism. Conclusion: Anterior segment optical coherence tomography may be used for evaluation of underlying primary angle closure mechanism(s) in a patient and tailor the treatment accordingly.