Optical coherence tomography for ophthalmic imaging: new technique delivers micron-scale resolution

The authors have developed a new technique for micron scale resolution cross-sectional imaging of ocular and other biological tissue, called optical coherence tomography (OCT). OCT is similar to B-scan ultrasonic imaging, except that image contrast relies on differences in optical rather than acoustic backscattering characteristics of tissue. In contrast to ultrasound and nonlinear optical gating techniques, low-coherence interferometry is used to resolve the position of reflective or optical backscattering sites within a sample. Two-dimensional tomographic images of a thin, optical slice of tissue may be obtained with 10 μm longitudinal and lateral resolution. Optical heterodyne detection and the application of noise-reduction techniques originally developed for optical communication achieve sensitivity to reflected light as small as 10/sup -10/ of the incident optical power. OCT is non-contact, non-invasive, and has superior resolution to conventional clinical ultrasound. Unlike scanning laser ophthalmoscopy and scanning laser tomography, the optical sectioning capability of OCT is not limited by the pupil aperture and ocular aberrations. OCT may be implemented in a compact, low-cost, fiber-optic based interferometer that is easily coupled to existing ophthalmic instrumentation. Here, the authors demonstrate high-speed in vivo OCT imaging in both the anterior and posterior eye, and highlight the system´s potential usefulness for the early diagnosis and quantitative monitoring of a variety of ocular diseases and treatments.