Clinical evaluation of the Humphrey automatic refractor.

A new automatic objective refractor was used on healthy adults. In the absence of cycloplegic drugs, spherocylindrical objective refractions performed with the instrument provided 20/20 acuity 96% as often as with standard subjective techniques. No instrument-induced accommodations effects were seen. One hundred percent of instrument spherical findings were repeatable within 0.50 diopters; all cylindrical findings were repeatable within 0.37 D. This result represents a higher level of repeatability than that reported for standard subjective refraction under clinical conditions. In the absence of cycloplegic drugs, the correlation coefficient between the instrument's findings and standard subjective spherical findings was .97 v .98 between two practitioners' subjective refractions. The average difference between cylindrical findings of the instrument and those of an experienced practitioner was 0.04 D larger than the average difference seen between two practitioners using subjective techniques.