Polarized vernier optometer

An optometer that makes use of polarized light and is based on the Scheiner principle is described. It is similar in construction and use to the better-known laser optometer, but it is less expensive, avoids some of the problems inherent in using lasers, and is responded to very well by subjects in behavioral research. Uses of the device are discussed, and the laser and vernier optometers are contrasted. It is concluded that the polarized vernier optometer is an economical and effective alternative to the laser optometer in behavioral research settings.