Date of Award


Degree Type


Degree Name

Master of Science in Vision Science

Committee Chair

Lee Ann Remington


A retrospective study was performed on 124 subjects to compare the results of different methods of refraction, namely automated refraction with the Epic 21 00® diagnostic system and subjective refraction preformed by either of two clinicians. After analyzing the data it was found that 90.7% of the autorefractor measurements of the spherical power were within +/- 0.25D, 93.5% within +/- 0.50D, and 97.9% within+/- 0.75D of the spherical component of the prescription found by subjective refraction. The results also showed that the cylinder components were similar between the two methods in that 95.1% were within+/- 0.25D and 97.5% within+/- 0.50D of each other. Results also showed that approximately 90% of all axis measurements were within+/- 5 degrees and 96% within+/- 20 degrees. It was concluded from these findings that the spherical and cylinder powers and axis results were not statistically different when comparing subjective and automated refractions. It was, determined that the cylinder axis results showed a poorer repeatability for low cylinder power than for higher cylinder powers. Bias may have been present in this study since the clinicians were not blind to the patient's previous prescription and clinicians may refine prescription end points differently influenced by their practice experiences.

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