BU College of Engineering Magazine
Spring 2004
Adaptive Optics
Some simple physiological facts have long stymied efforts to study many vascular diseases. “You basically cannot observe capillary blood flow anywhere in a person or other animal, because capillaries are deeply embedded in the body,” explains Tom Bifano, ENG professor and CTO of Boston Micromachines Corporation (BMC), “except through this one window you have, your eye.”
Unfortunately, the eye is not an ideal window through which to watch capillaries and microcapillaries in action. Even people with 20/20 or better vision have imperfect corneas and lenses in their eyes. As a result, capillaries on the order of 2 to 5 microns in size, while bigger than the diffraction limit of the eye, are smaller than the resolvable limit of human corneas. “Doctors could have a million-dollar microscope with all the best optics that Zeiss could make,” explains Bifano, “but the last objective is your eye, which has a lot of wonderful features, but also crummy resolution.”
Adaptive optics using BMC’s deformable mirrors has finally allowed ophthalmologists to get beyond those limits of the eye and to get a good look at blood flow in capillaries, and even microcapillaries, for the first time. In partnership with the University of Rochester, the Schepens Eye Research Institute, the National Institutes of Health and others, BMC and BU are contributing mirrors to the creation of a whole line of instruments to examine the human eye at the finest level. Already, prototypes have produced sharp, high-resolution images of the retina and what lies behind it. For understanding and treating vision diseases such as diabetic retinopathy and macular degeneration in particular, but also for all vascular diseases where drug delivery can now be studied, the new instruments may make all the difference.
The University of Rochester’s Center for Visual Science has collaborated with BMC and BU in a Biomedical Research Partnership on research into the next generation adaptive optics scanning laser ophthalmoscope (AOSLO), one of the suite of tools to incorporate BMC’s deformable mirrors. BMC sold CVS the mirrors that they used in that research. When Rochester’s Nathan Doble compared the imaging of a human retina using BMC’s deformable mirror to imaging of the same human retina done with a big piezoelectric mirror, “he showed that they’re comparable,” says Paul Bierden, BMC’s president and CEO, largely because the deformable mirror avoids the need for long optical path lengths and, as Bierden describes them, “these crazy off-axis paraboloid mirrors.”
“Just in December we saw the images of a mouse retina for the first time, and it was wonderful,” Bifano says of the progress on the AOSLO. “There’s the little mouse retina, with the little blood flow going through it.” Because all clinicians who work on eye disease use mice in their studies, Bifano predicts the AOSLO will be a powerful tool in their research. “Clinicians and researchers are going to be able to look at the retina better than they’ve ever been able to before,” he says.
The University of Rochester, BMC, and BU, Bierden contends, make for a great partnership. Rochester has long experience in adaptive optics for vision science but with a different focus than BMC and BU. “They’re coming at it from one end of the full optical system, kind of defining the sensing and controlling part of it,” he says. “We’re coming at it from the mirror and going up through the sensing and controlling part of it. Somewhere in there is where we are going to fit together a nice system where everyone is playing to their strengths and not duplicating efforts.” Indeed, researchers at the University of Rochester have already designed an award-winning MEMS-based AO phoropter that depends on BMC deformable mirrors.
“The technology is enabling researchers to do things that nobody could do before,” says Bierden. “We love that aspect of it.”
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BMC's deformable mirror |
