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S. K. Dorairaj, J. J. Rousso, C. Y. Cheung, H.-T. Li, R. Ritch, C.-P. Pang, D. S. Lam, C. K. Leung; Factors Associated With Scleral Spur Visibility in Anterior Segment Optical Coherence Tomography (ASOCT). Invest. Ophthalmol. Vis. Sci. 2008;49(13):2262.
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The scleral spur is an important landmark that can be visualized cross sectionally with ultrasound biomicroscopy or ASOCT. Identifying the location of the scleral spur is required for many measurements of iridocorneal angle parameters, including angle opening distance (AOD), trabecular iris space area (TISA) and trabecular iris angle (TIA). Poor delineation of the scleral spur is a major cause of angle measurement variability. We investigated the potential factors responsible for scleral spur clarity in ASOCT.
We analyzed 42 eyes of 42 subjects. Thirty-two eyes had open and 7 had narrow angles by dark room gonioscopy. ASOCT imaging was performed using a horizontal and a vertical scan at a position bisecting the pupil. Three images were captured in each orientation and the image with the best quality from each orientation was selected for analysis. A single grader assessed the clarity of the scleral spur as 0 (no visibility), 1 (blurred ) and 2 (clear delineation of scleral spur) for each quadrant. The total scleral spur delineation score (SSDS) was calculated by adding the individual score from each quadrant. The association between age, sex, axial length, refraction and the SSDS was evaluated with univariate and multivariate analyses.
The mean (Â±SD) SSDS at the superior, nasal, inferior and temporal quadrants were 1.76Â±0.43, 1.86Â±0.35, 1.05Â±0.70 and 1.90Â±0.30, respectively. The inferior quadrant had the worst delineation of the scleral spur compared with the others (p<0.001). No difference was found in the total SSDS between the open and narrow angle groups (p=0.443). The total SSDS was significantly associated with age (r=-0.483, p=0.001), axial length (r=0.421, p=0.006) and spherical error (-0.348, p=0.024). Multivariate analysis showed that age and axial length are the 2 significant independent predictors for scleral spur visibility.
The worst delineation of the scleral spur was found in the inferior angle, in older subjects and in eyes with short axial length. As age and short axial length are also risk factors for development of angle closure, further investigation is needed to determine the clinical significance of scleral spur visibility.
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