One pioneer in that effort was Francis L'Esperance, of the Columbia- Presbyterian Medical Center. In 1963 he began working with the ruby laser photocoagulator, using it in an attempt to treat diabetic retinopathy. The abnormal blood vessels in this disorder have weak walls and may break, clouding the vitreous and interfering with vision. They can also grow scar tissue that can pull the retina away from the back of the eye, causing severe vision loss, even blindness.

In early 1965 L'Esperance presented a paper at a conference in New York on the results of his work. One of the key things he noted was that blood absorbs only 6 to 7 percent of the ruby laser's red light, which meant that it took eight to 10 sessions to cauterize retinal blood vessels with the ruby photocoagulator. L'Esperance urged the development of a blue-green laser, whose light would be more highly absorbed by the blood vessels.

As it happened, such a laser, using ionized argon as the source, had been developed the year before. L'Esperance learned two weeks after the New York conference that Bell Laboratories had one of the devices. He persuaded Bell researchers Eugene Gordon and Edward Labuda to work with him in designing the optical and mechanical systems needed to deliver the argon laser's energy to the eye. Eventually, L'Esperance acquired a 10-watt argon laser from the Raytheon Corporation, and after further refinements and careful experiments, he treated a human with an argon-ion laser in February 1968. By the end of the month he had begun using it to treat patients with diabetic retinopathy.

About a year later, Dr. Arnall Patz of the Wilmer Ophthalmological Institute began using an argon laser to treat patients with diabetic and related retinopathies. Unlike the other pioneers in laser ophthalmology, Patz had no private corporate support. He had mortgaged his home and borrowed money to pay the Applied Physics Laboratory at Johns Hopkins University to build an argon laser for him. But by 1970 he had treated 285 patients for various retinopathies, and by the early 1970s Patz, L'Esperance, and Christian Zweng were jointly teaching other ophthalmologists how to use the argon laser.

The most effective treatment for diabetic retinopathy has proven to be a method called pan-retinal ablation. Advocated by Lloyd Aiello of the Joslin Diabetes Center in Boston, the method involves using a laser to ablate, or vaporize, scattered areas of the peripheral retina rather than coagulate blood vessels directly. Today, the treatment of diabetic retinopathy to prevent blindness is the leading application of lasers in ophthalmology.