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Dissertation

Comparison of Snellen letter and Vistech grating charts as refraction targets

1 May 1987

Abstract

Snellen letter and Vistech sine wave grating charts were used as refraction targets to determine differences in times required to accomplish subjective refractions, endpoint refractive values and subject preferences. Thirty hyperopes and thirty myopes, divided into three age groups, were selected as subjects. Two examiners tested each subject using each chart. Both timed their subjective refractions and recorded their findings. After all data were recorded, each subject completed a questionnaire to determine chart preference. There were no clinically significant mean differences between the charts in terms of endpoint refractive data, but, on average, the Snellen chart was faster to use. Chart rating depended on- the subject's refractive status with more myopes preferring the Snellen chart and more hyperopes rating the grating chart higher. KEY WORDS:


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