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FEIHUI ZHENG, Christopher Kai-Shun Leung; 360-degree measurement of anterior chamber angle dimensions in primary angle closure (PAC) with swept-source optical coherence tomography (SS-OCT). Invest. Ophthalmol. Vis. Sci. 2017;58(8):2083.
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Evaluation of the anterior chamber angle dimensions is crucial to the diagnosis and management of PAC diseases. While gonioscopy has been a reference standard for examination of the anterior chamber angle, reliable measurement of the anterior chamber angle width can only be attained with OCT. Yet, high resolution topography analyzing the distribution of the angle dimensions for 360° has not been investigated. We evaluated the test-retest variability of a new anterior segment SS-OCT (CASIA2, Tomey, Nagoya, Japan) for measurement of the anterior chamber angle and examined the 360° distribution of the angle dimensions in open angle eyes and in eyes with PAC diseases.
Anterior segment imaging was performed with CASIA2 SS-OCT (50,000 A-scans/s; 800 A-scans/B-scan) in 30 open angle glaucoma eyes (age: 55±11.5 years) and 30 eyes with PAC/PACS/PACG (age: 61.5±8.4 years). Each eye was imaged for three times (total scan time was 0.26sX3) in the dark. Angle opening distance (AOD) at 500µm from the sclera spur (SS) and trabecular iris space area (TISA) at 500µm from the SS were measured automatically by the software after manual detection of SS by two observers in 32 angle meridians. Comparisons of AOD/TISA between open-angle and angle-closure eyes were performed with ANOVA and Bonferroni correction. Inter-observer test-retest variabilities were evaluated with intra-class correlation coefficient (ICC).
The AOD/TISA measurements are shown in Fig. 1. AOD and TISA were significantly greater in open angle eyes than in PAC eyes in all 32 angle meridians (p<0.001). AOD/TISA were smallest at 45o-101o (superonasal meridians) in open angle eyes and at 56o-124o (superior meridians) in PAC eyes. The greatest difference in AOD/TISA between open-angle and PAC eyes was located at 180o-270o (inferotemporal meridians). ICC(AOD) and ICC(TISA) ranged between 0.817 and 0.982 and between 0.714 and 0.972, respectively, for eyes with open angle; and between 0.808 and 0.996 and between 0.779 and 0.985, respectively, for eyes with PAC.
The new SS-OCT is reliable for 360° measurements of the anterior chamber angle and differentiation between eyes with PAC and eyes with open angle.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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