had a brighter light, it was worth trying" for retinal surgery (reported in Hecht, 1992). Townes also recognized this potential in ophthalmology and wrote a paper in the early 1960s about possible medical and biological uses of the laser (Townes, 1962). But before the laser was considered for therapeutic work, researchers studied the potential danger of the laser to the eye.

FEAR OF INJURY

The physicists and engineers who invented and worked with the laser recognized its danger immediately. Accounts of retinal damage caused by staring at eclipses were reported by Plato and, more recently, many people had experienced retinal burns from watching the nuclear explosions at Hiroshima and Nagasaki. When doctors began treating vision-impaired residents of Japan they conducted systematic research on flash burns of the retina. Among these researchers were William Ham, Jr., and his associates at the Medical College of Virginia. His group, with support from the Defense Atomic Support Agency, studied flash burns on rabbit retinae in the late 1950s (Ham, Jr., et al., 1963). This research alerted ophthalmologists to the dangers of powerful light sources and resulted in government sponsorship of studies of the laser's effects. The government was interested both in ensuring the safety of scientists and technicians and in developing a laser weapon.

The first papers about the laser's risks appeared in Science on November 10, 1961. Two articles were published, one by Leonard Solon, Raphael Aronson, and Gordon Gould of TRG (Solon et al., 1961) and the other by Milton M. Zaret and his associates at the New York University Medical Center (Zaret et al., 1961). Zaret served as a medical consultant to TRG and Bell Labs and was pursuing two careers: one as an ophthalmologist and one as a researcher on the effects of radiation on humans. His primary interest was (and is) the relationship between nonionized radiation and cancer, and he had been a consultant to the military for radar and microwave research. His positions at TRG and Bell required that he examine the employees of these companies to determine what levels of exposure workers had to radiation. Because he communicated directly with the companies' researchers, he heard about new and ongoing research projects. He became aware of laser research in 1959 and understood the potential optical effects of a laser; he also understood the risk of injury the laser posed, especially to the eye. Zaret had "more than a casual knowledge of physics" (personal communication, Milton M. Zaret, May 1, 1992). He had been trained as an engineer during his military service in World War II and had written a graduate chemistry thesis on the structure of the atom, a subject that would now be in the realm of atomic physics. This interdisciplinary scientific education enabled him to fully understand the laser and its effects on human tissue; every ophthalmologist who developed laser photocoagulation systems in the early 1960s had a similarly strong knowledge of physics.



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