Optical Coherence Tomography in Ophthalmology: Development and Applications
James G. Fujimoto
Optical coherence tomography (OCT) was developed in 1991 and is rapidly gaining acceptance as a standard imaging tool in ophthalmology. OCT is analogous to ultrasound B mode imaging, except that it generates images by measuring the echo time delay of reflected or scattered light rather than sound. In ophthalmology, OCT enables real-time imaging of retinal pathology with resolutions that were previously impossible to obtain in vivo. In addition to enabling visualization of retinal structure, OCT can also perform quantitative measurement or morphometry of retinal architecture, such as retinal layer thickness or nerve fiber layer thickness.
Recently advances in OCT technology known as spectral / Fourier domain detection enable dramatic improvements in imaging speed. Commercial OCT instruments can now image at >25,000 axial scans per second, 50-100x faster than previous OCT systems, with resolutions of 5-7 um. Spectral / Fourier domain OCT has powerful advantages, including the ability to acquire high definition images with improved image quality, preservation of true retinal topography and improved retinal coverage. 3D-OCT data sets can be acquired and displayed analogous to MR imaging. OCT fundus images can be generated by axially summing 3D-OCT data, enabling precise and reproducible registration of cross-sectional OCT images to fundus features. Image data can be segmented to quantify retinal layer thickness and create topographic maps.
Advances in OCT technology also enable ultrahigh resolution imaging with axial resolutions as fine as ~2-3 um in research prototype systems. Retinal architecture, such as the inner and outer segments of the photoreceptor layers and retinal pigment epithelium can be visualized and quantitatively assessed. The ability to visualize photoreceptor morphology and its impairment is a promising marker of disease progression. Ultrahigh resolution OCT also enables imaging small animal models, such as the rat or transgenic mouse. The ability to non-invasively and reproducibly measure changes in retinal pathology in small animals over time promises to improve the efficiency of drug discovery and assessment. Functional OCT techniques are also being developed which may provide integrated structural and functional imaging. The newest research technology using frequency swept lasers for swept source OCT or new high speed CCD cameras for spectral domain OCT achieves even faster imaging speeds of >200,000 axial scans per second, 500x faster then previously technology. These advances promise to enable new research applications as well as enhance clinical ophthalmology. This presentation reviews the development of OCT and recent research advances.
James G. Fujimoto, Ph.D.
Department Of Electrical Engineering and Computer Science AndResearch Laboratory of Electronics
Massachusetts Institute of Technology
Cambridge, MA 02139
James G. Fujimoto obtained his bachelors, masters, and doctorate from the Massachusetts Institute of Technology in 1979, 1981, and 1984 respectively. Since 1985 he has been on the faculty of the Department of Electrical Engineering and Computer Science at M.I.T. where he is Professor of Electrical Engineering and Computer Science. His research interests include the development and application of femtosecond laser technology and studies of ultrafast phenomena. He is also active in biomedical optics and optical imaging. Dr Fujimoto’s group and collaborators were responsible for the invention and development of optical coherence tomography (OCT) imaging.
Dr. Fujimoto co-founded the startup company Advanced Ophthalmic Devices, which developed OCT for ophthalmic imaging and was acquired by Carl Zeiss. He is also co-founder of LightLabs Imaging, which develops cardiovascular and endoscopic OCT and was acquired by Goodman, Ltd. Dr. Fujimoto was awarded the Discover Magazine Innovation Award for Medical Technologies in 1999, and was co-recipient of the Rank Prize in 2002. Dr Fujimoto is a member of the National Academy of Science, National Academy of Engineering and American Academy of Arts and Sciences.