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S. F. Sandler, S. Dorairaj, C. Tello, R. Ritch, J. M. Liebmann; Provocative Testing in the Era of Imaging: Slit-Lamp Adapted Optical Coherence Tomography (SL-OCT) vs. Ultrasound Biomicroscopy (UBM). Invest. Ophthalmol. Vis. Sci. 2007;48(13):873.
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© ARVO (1962-2015); The Authors (2016-present)
To compare UBM, SL-OCT and gonioscopy for assessment of anatomically narrow angles (ANA).
Eyes with ANA (Shaffer grade ≤ 2) were imaged under light and dark conditions using SL-OCT and UBM. Angle opening distance at 500 microns (AOD 500) was recorded using each device for superior and inferior angles. SL-OCT and UBM images and gonioscopy under dark conditions were assessed for iridotrabecular contact (ITC). Sensitivity, specificity and predictive values were evaluated; Kappa statistic was used to measure reproducibility between devices.
Mean patient age was 59.2 ± 12.6 (SD) years and mean refractive error was +1.4 ± 1.2 D (range -0.50 to +4.50 D). In both superior and inferior angles, AOD 500 was less when measured by UBM compared to SL-OCT. Differences between instruments were highly significant in the inferior angle in light and dark conditions (paired t-test, all p<0.0001). In the superior angle, a highly significant difference was seen in light (p=0.002), but not in the dark (p=0.153). When controlled for light and dark conditions, differences remained highly significant for superior (p=0.006) and inferior angles (p<0.001, two-way analysis of variance). Specifying UBM as the gold standard for ITC, SL-OCT had 80% sensitivity and 87% specificity in the superior angle; sensitivity was 100% with 62% specificity in inferior angle. Gonioscopy had 95% and 85% sensitivity in the superior and inferior angles, respectively, with a specificity of 67% in both locations. Both UBM and SLOCT showed good reproducibility with kappa values ranging from 0.65 to 0.47.
Multiple factors influence the appearance of the angle, including method of assessment, the software used to process images, illumination, patient posture and contact during the procedure. SL-OCT appears to underestimate the frequency of ITC. Differences in detection of ITC among devices require careful investigation, especially if SL-OCT is to be considered as a screening tool or a gold-standard for the detection of angle-closure.
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