Otto Wichterle, a Czechoslovak chemist who in 1961 used an Erector set and a phonograph to produce the world's first soft contact lenses, died yesterday at his summer home in Sdradisko, a Moravian village in the Czech Republic. Dr. Wichterle, a former president of that nation's Academy of Sciences, was 84 years old.

Dr. Wichterle died in his sleep after having suffered a heart attack and a stroke within the last year, according to his grandson, Hynek Wichterle, a doctoral candidate in neurobiology at Rockefeller University.

The consequences of Dr. Wichterle's kitchen-table experimentation changed the way millions of people see and look. ''Before his discovery, there were, of course, contact lenses,'' said Dr. Dwight Cavanaugh, a professor of ophthalmology at the University of Texas Southwestern Medical Center at Dallas. ''But they were made of glass or hard plastic. They were difficult to make and to fit and probably no more than 10,000 or 20,000 were being used. As a result of what Dr. Wichterle achieved, a billion-dollar industry came into being; today there are about 30 million people in the United States and 100 million people around the world who use soft lenses.''

As explained by his grandson, the discovery came about in a difficult period for his grandfather. Until 1958, Dr. Wichterle had been the dean of the Institute for Chemical Technology in Prague, having acquired dozens of patents for various polymer materials, among them Silon, a substance similar to nylon that he developed in the late 1940's. But in that year Communist Party officials dismissed him from his position, calling him politically unreliable.