David Maurice, 80, a doctor who specialized in eye research, died of a liver tumor July 20 in New York City. A professor of ocular physiology at Columbia University, he invented a device used to examine the cornea called a specular microscope. It is used throughout the world in procedures including cataract removal and laser eye surgery. Maurice also published a paper in the mid-1990s that argued that rapid eye movement during sleep -- commonly thought to be a sign of vivid dreams -- is caused by the eye's need for oxygen.