Corning Glass Works agreed to purchase U.S. Precision Lens of Cincinnati for an undisclosed number of shares of Corning common stock, a spokesman said. U.S. Precision is a privately held manufacturer of plastic optics. The company, owned since 1970 by its management team, makes optics for projection television sets, video cameras, fiber optics and automotive dashboard displays. Corning Glass, with worldwide sales of $1.7 billion in 1985, focuses on telecommunications, laboratory sciences, specialty glass and ceramics and consumer housewares.