3D anterior chamber angle measurements with high resolution Fourier-domain optical coherence tomography

In this article, an automatic method for measuring 3-dimensional (3D) anterior chamber eye angle opening distance (AOD) with Fourier-domain optical coherence tomography (OCT) was proposed. A special 3D "Angle Arc" scan pattern composed of 25 cross-sectional OCT image frames was designed. The initial boundaries of the anterior and posterior cornea and anterior iris were located in all the frames and then refined. Human input was needed to identify Schwalbe's line (SL) in 3 key frames of each 3D dataset. Next, the computer algorithm was employed to estimate SL locations in the rest 22 frames according to a mapping method. Last, the angle opening distance based on the SL (AOD-SL) was calculated for all the frames. Result showed that the computer algorithm provided a robust and accurate method to measure 3D AOD-SL. The precise angle boundary detection was 96.06% in image frames, and accuracy of the AOD-SL measurement in the key frames was 95.11% by using the automated AOD-SL measurements. The automated AOD-SL measurements agreed well with the human measurements with computer calipers.