Technical Refinement of the Vernier Optometer

摘要

The need for precise lens accommodation to bring visual targets into sharp focus on the retina is far more urgent at night, when contrast is very low, than in bright daylight. However, it is at precisely this time that many individuals become myopic and further reduce the quality of an already poor visual image. For pilots flying at night, this phenomenon can mean the difference between life and death. A reliable screening instrument capable of measuring the refractive state of individuals in the dark could, therefore, provide useful preventive information. Such an instrument should be simple, easy to use, and produce accurate results within a short period of time. Currently, much research in the area of dark focus has relied on the laser-Badal optometer. This device is simple and produces accurate results. It is however, quite difficult to use in practice. Some individuals are completely unable to produce data with this device. An alternative optometer uses polaroids and a vernier task, hence the name vernier optometer. This device is simple to both construct and use. However, a vernier optometer design provide by Dr. Robert Hennessy, of Monterey Technologies, Inc., did not reliable produce accurate results, at least as it was implemented at our laboratory. We saw a number of ways to improve the design of this vernier optometer. We believe we were successful in this endeavor and describe our new design here. (mjm/aw)