Patient Care Bio
Research Interests
I use psychophysical, anatomical, and imaging techniques to study how the structure of the eye and brain affects visual experience. My Ph.D. thesis at the University of California, San Diego was completed under the direction of Donald I.A. MacLeod in 1979. In collaboration with Mary Hayhoe, we mapped the distribution of individual short-wavelength-sensitive photoreceptors in the human retina. These experiments demonstrated that it is possible to stimulate a single photoreceptor with light in the living human eye. They also showed that only 10 photons absorbed by a single photoreceptor are necessary to produce a visual sensation. In 1979 I joined the Technical Staff at Bell Laboratories in Murray Hill, New Jersey, working with John Krauskopf. We used a three-laser colorimeter to study the opponent mechanisms that underlie human color vision. In 1981, I joined the faculty at the University of Rochester. During my early years at Rochester I developed a new laser interferometer to stimulate the retina with interference fringes that are not blurred by the optics of the eye. Looking into this instrument, observers could detect interference fringes at very high spatial frequencies because of aliasing by the photoreceptor mosaic. These observations revealed clearly for the first time the theoretical limitations predicted by sampling theory on human visual resolution and allowed the first measurements of the spacing of cones in the living human eye. Walt Makous, Donald MacLeod, and I have also used interference fringes to measure the sizes of receptors in the living eye.
Current research projects in my laboratory use wavefront sensing and adaptive optics to explore the optical quality of the eye and the organization of the human retina. We measure the aberrations of the eye with a Hartmann-Shack wavefront sensor, first developed by Junzhong Liang. These measurements are used to control the shape of a deformable mirror. This mirror can be warped into the appropriate shape to correct most of the eye's aberrations, providing the eye with the best image quality ever achieved. When a subject looks through the mirror, psychophysical experiments can be performed to study the optical and neural limits on human vision. When the experimenter looks through the mirror at the subject's retina, he has a much sharper view of the retina than has ever been possible before. With this and other advanced imaging techniques, J. Liang, Don Miller, Mike Morris, and I have been able to resolve features at the spatial scale of single cells for the first time in the living retina. Adaptive optics may ultimately prove valuable in the diagnosis and treatment of retinal disease. Wavefront sensing has interesting applications for improving contact lens design and we are working closely with Ian Cox to fabricate lenses that correct vision better than conventional designs. We are also working closely with Scott MacRae to improve the outcome of laser refractive surgery based on wavefront techniques.
