Major research findings often quickly follow the invention and development of a new or better method of measuring something, thereby contributing to science and industry. Hennessy's development of the laser optometer in 1970 led to an explosion of research findings that substantially revised our century-old conception of the visual accommodation process and its functional significance. Laser optometers and the more sophisticated infrared 3-D eyetrackers are excellent laboratory devices, but they are expensive, hard to use, and unsuited to operation in applied settings in which people perform real-world visual tasks. Another major drawback of these devices is that the subject using it does not know when he is out of alignment because he cannot see the measurement light. Thus, small pupils are a large problem. Our proposed device circumvents that difficulty. In 1979, Simonelli, at the University of Illinois, developed a prototype optometer that substituted polarized light for laser light and proved equally or more effective in the laboratory. We propose to investigate the potentional application of the principle of the "polarized vernier optometer" to the definition of a compact, light-weight, safe, accurate, and relatively inexpensive eye-focus measurement device that will be easy to use in applied settings and will neither affect what is being measured nor interfere with the performance of real-world visual tasks such as driving, flying, and operating computer terminals.