The director emeritus of the Wilmer Eye Institute at Johns Hopkins, he was considered a pivotal figure in the history of ophthalmology. His work won him a Presidential Medal of Freedom in 2004 and a Lasker Award for his research into the causes and prevention of blindness.
As a young doctor training in Washington, D.C., after World War II, Patz observed that a new incubator, sealed to contain an inner climate, was enabling doctors to save premature babies
"But something was wrong," Patz said in a 2004 Baltimore Sun profile. He noticed that the advance coincided with an epidemic of infant blindness and that most of the victims were "preemies" who lay for weeks in an atmosphere of near-total oxygen.
In a question that outraged physicians at the time but later won their admiration, Patz asked whether there might be a connection: Was it possible that oxygen was robbing babies of their sight?
"It had become standard practice to put babies in incubators and crank up the oxygen," Patz said in the Sun interview. He said that he could hardly blame the doctors who did this because it turned struggling babies from blue to pink.
His research revealed that the excess oxygen given premature babies caused a disease called retrolental fibroplasia, then the major cause of blindness in children.
Patz sought funding for what became one of the first clinical trials in all of medicine. His idea was to follow preemies given high oxygen and others experimentally given lower doses. When one funding agency considered his proposal unscientific and possibly dangerous, he conducted his own trial.
Seven of 29 babies maintained on high oxygen developed advanced eye disease, while none of 37 babies on low oxygen did.
It was discovered that oxygen caused blood vessels in the back of the eye to constrict. In a doomed attempt to compensate, the eye sprouted twisted vessels that would eventually bleed and destroy the retina.
In 1956, he shared the Lasker Clinical Medical Research Award with V. Everett Kinsey, a biochemist who organized a larger study that confirmed his findings. Handing them their trophies was Helen Keller, the renowned deaf and blind woman who became one of his inspirations.
"Helen Keller's eyes were so sparkly," he said in the 2004 Sun interview.
Patz also collaborated with the Johns Hopkins Applied Physics Laboratory on one of the first argon lasers used in the treatment of diabetic eye disease and other retinal disorders.
"He was an exceptional colleague and friend, whom I consider to be one of the greatest ophthalmologists and greatest human beings in modern medicine," said Dr. Morton F. Goldberg, who succeeded him at Wilmer. "It was his passion, as well as his brilliance, that made him a great researcher and clinician, and most importantly, a mentor to all of us who learned and worked with him."
Born June 14, 1920, in rural Elberton, Ga., to shopkeepers, Patz earned his medical degree at Emory University, served at Walter Reed Army Medical Center and trained at D.C. General Hospital.
He moved to Baltimore in 1950, where he married Ellen Levy.
Patz maintained a private ophthalmology practice while serving as a part-time faculty member at Hopkins for 15 years before the Seeing Eye Foundation awarded him a research professorship at Wilmer in 1970, when he joined the faculty full time as founder of Johns Hopkins' Retinal Vascular Center.
He also earned a master of liberal arts degree from the Johns Hopkins Krieger School of Arts and Sciences when he was 78.
Patz is survived by his wife of 60 years; a daughter; three sons; and eight grandchildren.