The New York Times The New York Times Technology September 12, 2002  

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For an Irregular Lens, an Optical Blueprint

By MARC WEINGARTEN

AS a computer graphics specialist, Brian A. Barsky has conjured up intricately rendered worlds on a PC screen. But in the real world, he has trouble seeing in the dark, and occasionally in broad daylight. For the last 27 years, Dr. Barsky, a professor of computer science and an affiliate professor of optometry at the University of California at Berkeley, has suffered from keratoconus, an abnormal thinning of the cornea that can wreak havoc with depth perception and night vision.

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For years, Dr. Barsky sought a remedy for his vision problems. Then, while on sabbatical in 1992, he realized that a solution for keratoconus patients might be found in the complex algorithms of computer graphics.

An early teacher of computer graphics imaging technology whose students have gone on to work for Pixar Animation Studios and for Lucas Digital's Industrial Light and Magic, Dr. Barsky has devoted much of his professional life to the study of splines, the algorithms that are used to render curved surfaces on computer screens. Spline mathematics subdivides complex computerized shapes into smaller component pieces, with each piece defined by its own equation. Dr. Barsky figured out how to use splines to create a highly detailed digital template of the human cornea. Using this optometric blueprint, he created custom-designed contact lenses.

Conventional contact lenses have simple shapes and are usually symmetrical: they cannot account for irregularities in the cornea's shape. Dr. Barsky's custom-made contact lens fits precisely over an abnormally shaped cornea.

By using a common eye measurement instrument called a corneal topography device with the same spline equations that are used to create cinematic special effects, doctors could one day measure the cornea's surface down to the tiniest micron. Maps based on the measurements could be used to create customized contact lenses for people suffering from keratoconus, eliminating the need for invasive surgery.

"Normally with corneal topography, if I move my eye, the measurements will change, which is incorrect, since my eye did not really change shape," said Dr. Barsky, who is talking with contact lens companies that are interested in his invention. "If we take that same input and run it though our more sophisticated mathematical approach, we'll get a more accurate profile of the cornea. The measurements remain the same even for different gaze directions."

Lens makers are optimistic. "Dr. Barsky is at the center of a turning point in our industry," said William E. Meyers, vice president for science and technology at Paragon Vision Sciences, a contact lens company in Mesa, Ariz. "For years, we have speculated about how to design contact lenses to manage the wide array of clinically observed corneal distortions. Not only does Dr. Barsky deliver the math, but he pursues the goal with the passion of a man whose own vision is challenged by just such an ocular complication."

Dr. Barsky's spline-based model could also improve the accuracy of Lasik surgery, in which part of the cornea is cut and peeled back and the underlying tissue is reshaped by a laser. People whose eyes are unsuitable for Intacs, tiny crescent-shaped inserts that are implanted in the cornea to flatten the curvature and correct nearsightedness, could also benefit, as could those with eye ailments like astigmatism.

Dr. Brian Boxer Wachler, director of the Laser Refractive Center at the Jules Stein Eye Institute at the University of California at Los Angeles, said the spline-based design could be useful to people who must wear contact lenses but cautioned that such specialized lenses could be too expensive to manufacture. "That could be the edge on the double-edged sword," Dr. Boxer Wachler said. "If you have to make a special lens for each eye, it's a lot more expensive, versus using a standard lathe that produces uniform lenses."

But Dr. Barsky is convinced that the market is large enough nearly one million Americans suffer from corneal abnormalities to support a custom-made lens industry. "Most people buy contact lenses for cosmetic or convenience purposes," he said. "This is important for those who need lenses that are medically necessary as the only hope to provide good vision and avoid a corneal transplant."




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Peter DaSilva for The New York Times
CUSTOMIZED - Brian A. Barsky, professor of computer science, with a device that maps his deteriorated cornea.


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