Optical coherence tomography (OCT) is a new type of medical diagnostic imaging modality that performs high-resolution, micron-scale, cross-sectional tomography imaging of ocular structures in vitro and in vivo.1 Researchers at Harvard, the Massachusetts Institute of Technology, and Tufts University developed this technology. The first commercial device for use in posterior segment structures became available in 1995 (Humphrey Instruments, Dublin, CA). The OCT image has an axial resolution of 10 μm, and this resolution is significantly higher than those achieved by the scanning laser ophthalmoscope, B-scan ultrasound, and ultrasound biomicroscopy (UBM), which have image resolutions of 300, 150, and 20 μm, respectively.2 © 2009 Springer New York.