Comparison of Anterior Segment Optical Coherence Tomography and Ultrasound Biomicroscopy for Assessment of the Anterior Segment of the Eye

Abstract

Anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) allow imaging of anterior ocular structures. Anterior segment optical coherence tomography produces images similar to B-mode ultrasound imaging using light instead of ultra-sound. Optical coherence tomography technology, which originally was used in ophthalmology to image the posterior segment, has also been used to image anterior segment structures such as the cornea. However, the wavelength of this technology (0.8 μm) is insufficient to allow penetration of the sclera and, therefore, imaging of the anterior chamber angle. In addition, image acquisition at this wavelength is slow. A new anterior segment OCT system has been introduced recently that uses a longer wavelength (1.3 μm), allowing deeper penetration and cross-sectional imaging of the anterior chamber and visualization of the angle. The scanning speed of this new system is 40 times faster than previous anterior segment OCT systems, enabling real-time imaging. This new AS-OCT system has the benefits of being a rapid noncontact method that may be performed by a technician. AS-OCT has many applications in corneal disorders, In Keratoconus, AS-OCT has micron-level high resolution and can accurately map the corneal thickness which is a corner stone in diagnosis of keratoconus.