Flat-panel displays, especially liquid crystal displays (LCDs), are almost universally used today. Do LCDs assure better readability than cathode-ray tubes (CRTs)? Two experiments were carried out to determine which type of display is better using a newly developed device. Four types of displays were tested; negative and positive CRTs, and LCDs with and without backlighting. Variables were the type of display, age, and gender. At first, analyses of readability using eye movements were conducted. Middle-aged subjects showed slower reading speed than young subjects. Then, experiments of pupillo-accommodative functions were carried out. Non-backlit LCDs reduced focusing speed among young subjects and reading performance in middle-aged subjects. Since middle-aged workers have more difficulties than young workers, they should have their vision properly corrected for VDT viewing, more appropriate displays and a more comfortable illuminance environment than young workers.