A focometer is an instrument that measures refractive errors and is intended to provide rural or economically disadvantaged populations spherical eyeglass prescriptions without the need for complicated protocols, expensive equipment, or electricity.
[2] A study has found, however, that the focometer is less effective for identifying astigmatism than an autorefractor, and that its axis accuracy is limited to 15°.
[4] The advantages of a focometer over other methods for use in developing countries are that it is lightweight, compact, relatively inexpensive, fairly quick, and easy to use with minimal training.
A clinical trial compared the repeatability, validity, and ease of use of the focometer with an autorefractor.
The authors found that repeatability of the measurements improved when patients were allowed to "practice" twice on each eye before taking the real reading.