Sensor could increase safety of eye surgery

November 30, 1999

RICHLAND, Wash. - Precision is crucial during eye surgery - a slight miscalculation could result in partial blindness and damage to the retina. But a new sensor being developed at the Department of Energy's Pacific Northwest National Laboratory could reduce those risks by alerting surgeons to the location of critical retinal tissues.

Pacific Northwest researchers have designed and built a proximity sensor that could be connected to an endoscope, the tool surgeons use when operating on the back of the eye. The sensor calculates distance of the endoscope's needle to the retina and tissue.

Pacific Northwest is teaming with Johns Hopkins University's Microsurgery Advanced Design Laboratory, or MADLAB, and Insight Instruments Inc. of Sanford, Fla., through a Cooperative Research and Development Agreement to share costs and results associated with the proximity sensor. MADLAB is expected to conduct surgical tests of the sensor, while Insight Instruments Inc. plans to incorporate the device into endoscopes it manufactures.

"Many surgeons are apprehensive to use an endoscope because they don't know the proximity of the tool to crucial eye materials," said Peter Luloh, president of Insight Instruments Inc. "This sensor could alleviate those concerns by alerting them when the tool approaches the retina, for example."

The proximity sensor also could be applied to other surgery, such as spinal operations that require surgeons to know the location of nerves.

Pacific Northwest researchers built a proximity sensor that relies on a fiber smaller than a strand of hair to transmit and receive light. The system begins by sending electricity into a laser diode, which connects to a fiber. The diode converts electricity into light, which then bounces back and forth along the fiber's walls until reaching the retina.

The retina absorbs about 80 percent of the energy and reflects the remaining 20 percent back to the proximity sensor. The reflected light travels back through the fiber to a photo diode, which converts the light into an electrical signal. An electronic circuit translates the voltage level into distance. If the distance reaches two millimeters or less, the system would trigger an audible alarm to alert the surgeon.

Pacific Northwest researchers tested this proof of concept in the laboratory in 1998. They are building a second-generation proximity sensor to incorporate issues specific to eye surgery. For example, because the eye is extremely sensitive, the laser cannot exceed 37 microwatts, or .0037 percent of one watt.

The MADLAB expects to conduct tests on patients next year. DOE funded development of the proximity sensor with $70,000.
Business inquiries on this and other PNNL technologies should be directed to 1-888-375-PNNL or e-mail:

Pacific Northwest is one of DOE's nine multiprogram national laboratories and conducts research in the fields of environment, energy, health sciences and national security. Battelle, based in Columbus, Ohio, has operated Pacific Northwest for DOE since 1965.

DOE/Pacific Northwest National Laboratory

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