Objectives  To use angle opening distance at the Schwalbes line (AOD-SL) as a parameter to help assess angle closure risks using Fourier-domain optical coherence tomography (OCT).
Methods  An 830 nm wavelength Fourier-domain OCT (RTVue, Optovue, Inc.) was used to perform horizontal scans of the nasal and temporal anterior chamber angles in glaucoma subjects. Images were graded by two ophthalmologists who assessed the visibility of Schwalbe’s line (SL), anterior limbus (AL), scleral spur (SS), and angle recess (AR) and measured AOD-SL with computer calipers. SL was manually identified by the termination of the corneal endothelium. Gonioscopy was performed by a glaucoma specialist and classified using modified Shaffer system. Spearmans rho were performed to assess correlation between AOD-SL and Shaffer grade. A cut-off value of AOD-SL for diagnosing occludable angles was determined by receiver operating characteristic (ROC) analyses.
Results  Thirty five subjects (65 eyes) were enrolled. SL, AL, AR, and SS were visible in 97.7%, 99.2%, 87.3% and 80.8% of eyes, respectively. AOD-SL were 322.6 ± 200.2 microns (nasal) and 341.4 ± 197.4 microns (temporal). Correlation coefficients between AOD-SL and Shaffer grade were 0.80 (nasal) and 0.81 (temporal). The diagnostic cut-off value of AOD-SL for occludable angles was 290 microns. The AROC/sensitivity/specificity values were 0.90/ 0.80/ 0.87 (nasal) and 0.90/ 0.85/ 0.77 (temporal).
Conclusions  The measurement of AOD-SL by Fourier-domain OCT is highly correlated with gonioscopy and may be useful as a noncontact method of assessing angle closure risk.