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N. Shabana, M. C. D. Aquino, J. L. S. See, Z. Ce, A. M. Tan, S. C. Loon, P. T. K. Chew; Quantitative Evaluation of Anterior Segment Parameters Using Anterior Segment Ocular Coherence Tomography (ASOCT) to Study Different Mechanisms of Angle Closure. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5547.
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© ARVO (1962-2015); The Authors (2016-present)
To quantitatively evaluate anterior segment parameters using ASOCT to study different mechanisms of angle closure.
A total of 148 patients (148 eyes) with primary angle closure and primary angle closure glaucoma were recruited from National University Health System, Singapore. With consensus of 4 glaucoma experts the eyes were categorized into 4 groups based on the anatomical mechanisms of angle closure. 51 eyes with pupil block, 23 eyes with Plateau Iris (PI), 21 eyes with thick Peripheral Iris Roll (PIR) and 53 eyes with Large Antero-posterior Lens Diameter (LAPLD). All patients underwent complete ophthalmic examination and ASOCT nasal-temporal images were captured under dark conditions. Using customized software the following parameters were computed: Anterior Chamber Area (ACA), Lens Vault (LV), Anterior Chamber Depth (ACD) central, ACD 1000, 2000 (ACD at 1000 µm and 2000 µm from the scleral spur respectively), Angle Opening Distance (AOD) 500 and 750, Angle Recess Area (ARA) 1000, 2000 (sector area between anterior iris surface and corneal endothelium with 1000 µm and 2000 µm radii from scleral spur respectively), Scleral Spur Distance (SSD) and Trabelcular Iris Space Area (TISA) 500 and 750.
Using ASOCT we found a significant difference in ACA, LV, central ACD, ACD 1000, 2000 between the groups (P< 0.001). ACA was largest in PI eyes (P<0.001) and smallest in LAPLD eyes (P<0.001). LV was thickest in LAPLD eyes (P<0.001) and thinnest in PI eyes (P<0.001). Central ACD was deepest in PI eyes (P<0.001) and shallowest in LAPLD eyes (P<0.001). ACD 1000, 2000 was deepest in PI eyes (P<0.001) and was shallowest in PIR eyes (P<0.001). AOD 500, ARA 1000, SSD and TISA 500, 750 showed no significant difference between the groups. However, AOD 750 showed the widest angle for PI eyes (P<0.001) and ARA 2000 was largest in PI eyes (P<0.001).
The PI eyes have largest ACA, ACD and ARA. The LAPLD eyes have thickest lens vault and shallowest ACD and ACA. We can infer that ASOCT can be a useful tool in quantitative evaluation of underlying mechanisms of angle closure in an Asian population.
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