Assessment of scleral spur visibility with anterior segment optical coherence tomography

To develop a grading system to evaluate the scleral spur visibility and to investigate the association between this and the angle width.

Sixty healthy normal subjects (33 with open angles and 27 with narrow angles on dark room gonioscopy) underwent anterior segment imaging with the Visante OCT (Carl Zeiss Meditec, Dublin, CA). The anterior chamber angles at 12-o' clock hour positions were imaged and analyzed. The scleral spur at each clock hour position was independently graded by 2 observers. A scleral spur visibility score (SSVS) of 2 denotes clear visibility of the scleral spur. SSVS of 0 and 1 represent undetectable and moderately by visibile scleral spur, respectively. The interobserver agreement of the SSVS was evaluated with kappa statistics. The associations between age, sex, axial length, refraction, angle width [mean anterior chamber angle detection with edge measurement and identification algorithm (ACADEMIA) angle], and the mean SSVS were examined with univariate and multivariate analyses.

The mean gonioscopy grades were 3.6 and 0.8 for the open and narrow angle groups, respectively. The interobserver agreement in grading the scleral spur visibility was 0.71. The inferior angle (6:00) had the worst visibility of the scleral spur (SSVS=1.05+/-0.49) whereas the scleral spur of the nasal angle (3:00) showed the best visibility (SSVS=1.66+/-0.46). There were significant differences between SSVS at 6:00 and the other clock hours except for 5:00 and 7:00. The mean SSVS correlated positively with gonioscopy grade, anterior chamber depth, and ACADEMIA angle, and negatively with age. The only significant factor associated with scleral spur visibility was the ACADEMIA angle (P=0.013) after adjustment for other covariates.

The visibility of the scleral spur is an important determinant of the dimension of anterior chamber angle.