Adaptive optics, a technique used to peer into the center of the Milky Way, is now turning its gaze on tiny blood vessels in the eye and neurons in the mouse brain, experts said at a symposium at the 2011 AAAS Annual Meeting.

The sight of a star--or cell--is never a perfect one, as light waves bounce and bend in unpredictable ways as they make their way from the object to the eye. Adaptive optics measures and compensates for these deflections to create a sharper image.

Christopher Dainty, a professor of applied physics at National University of Ireland in Galway, compared the technique to "taking a crinkled potato chip and flattening it without crumbling it."

First proposed in 1953, adaptive optics research accelerated in the 1970s and 1980s as U.S. defense researchers looked for ways to build better weapons guidance systems. After many of the military studies were declassified in the early 1990s, astronomers quickly seized on the technique to build telescopes that could correct light waves distorted as they passed through Earth's atmosphere.

Today's applications for adaptive optics have become more earthbound, but no less impressive. 

The technique is transforming vision research, said Joseph Carroll, an associate professor of ophthalmology at the Medical College of Wisconsin, Milwaukee. Researchers can now follow the flow of blood within a single capillary in the retina, he said, and have used the technique to study the complete assortment of rod photoreceptors within the eye.

The images can be used to track the loss or damage of individual eye cells, Carroll said, "and really give a patient or a doctor an idea of how vision is changing over time."  This could prove especially useful in designing therapies for diseases such as diabetic retinopathy, Carroll said, where retinal damage and blindness can be avoided if caught in time.


Eric Betzig turned to adaptive optics when he needed a way to see individual cells buried deep in the brains of living mice. The  Howard Hughes Medical Institute researcher and his colleagues at the Janelia Farm Research Campus seeded the brain tissue with tiny fluorescent beads to act as "guide stars"  that allowed them to measure the deflections of light rays one at a time.

"The brain's not transparent, it's a slice of tofu," he joked. "It's sort of like trying to get an adaptive optical correction of a star, if the star were behind a cloud."

Astronomers themselves still have big plans for the technique. Norbert Hubin, adaptive optics group leader for the European Southern Observatory, said new experiments confirm that adaptive optics can be used to improve a "large-field view" where starlight from many directions can be observed at once. He said adaptive optics will be a significant part of the proposed 42-meter European Extremely Large Telescope.

Betzig and others hope for similar large-field view experiments at the microscopic level. "We're always three steps behind what these [astronomers] are doing," he said admiringly, "but we learn a lot from them."