Imaging the Retina Using OCT and Adaptive Optics
Donald T. Miller
Microscopic imaging of the living human retina has experienced dramatic advances in recent years, owing in large part to the application of OCT and adaptive optics (AO) to the eye. OCT provides high axial resolution and sensitivity, while AO offers the complementary high transverse resolution. In principle, the combination of the two should yield sufficient resolution and sensitivity to visualize many of the cellular structures in the retina in all three dimensions. Two such structures we have recently focused on are the individual nerve fiber bundles and the smallest capillaries in the retina. These structures are destroyed in glaucoma and diabetic retinopathy, respectively, yet are difficult to observe with current clinical techniques. To this end, we evaluated the capability of ultrahigh resolution (UHR) AO-OCT to (1) differentiate individual nerve fiber bundles in all three dimensions at various locations across the retina surface and (2) detect the smallest capillaries in the retina such as those in the parafovea region that surround the foveal avascular zone.
Parallel to this effort, we have also developed a high-speed AO ophthalmoscope for detecting physiological changes in the photoreceptor layer. Use of temporally-coherent light for imaging enables exquisite, sub-micron sensitivity to optical path length changes in the photoreceptor outer segments. With this instrument, fast (msec), stimulus-evoked changes in the reflectance of cones are observed, changes that are on the same time scale as the phototransduction process. Much slower (hours), non-stimulus-evoked changes are also observed, changes that are closely matched to the expected renewal rate of outer segment discs. Results to date suggest that UHR-AO-OCT and AO ophthalmoscopy are promising new tools for probing noninvasively retinal structure and function at the microscopic level.
Donald Miller, Ph.D.
Associate Professor of Optometry and Vision Science
Donald Miller received his BS in applied physics from Xavier University in 1988. He pursued his PhD at The Institute of Optics at the University of Rochester, where much of his thesis was conducted in the Center for Visual Science. As a postdoctorate at the same center, he was instrumental in the development of the first adaptive optics (AO) instrument for correction of ocular aberrations for retinal imaging and vision applications. From 1996 to 1998 he was a National Research Council Research Associate in the Electro-Optics Sensor Technology Branch at Wright-Patterson Air Force Base in Dayton, Ohio where he worked on laser radar systems. He joined the faculty at Indiana University School of Optometry in 1998 and is currently at the rank of Associate Professor.
Dr. Miller’s research interests are in high-resolution retinal imaging, assessment and correction of ocular aberrations, ophthalmic optics, and the general application of advanced optical techniques to the eye. He is a founding member of the Center for Adaptive Optics, a consortium of university, government, and industry researchers funded by the National Science Foundation, now in its 10th year. He is also a member of a NIH Bioengineering Research Partnership (in its sixth year) hosted at the University of California, Davis. At Indiana University Dr. Miller has pioneered the development of high-resolution optical systems for imaging the ocular fundus based on the combined technologies of adaptive optics and optical coherence tomography. His group has also made pioneering advancements in high-speed adaptive optics fundus cameras. The cameras have opened a new window of opportunity to study structure and function of the retina at the cellular level in normal and pathologic eyes. Further information is available at http://www.opt.indiana.edu/people/faculty/miller.htm.