Reliability of refraction--a literature review.

The repeatability (reliability) of methods of measuring refractive error is an important consideration in patient management decisions and in research design and interpretation. Several papers on reliability of refraction have appeared in the literature.Studies on the reliability of conventional clinical refraction, including repeated refractions by the same examiner (intraexaminer reliability) and comparisons of the results obtained by different examiners (interexaminer reliability), were reviewed. Studies comparing the results obtained by autorefractors and conventional subjective refraction were also reviewed.The intraexaminer reliability and interexaminer reliability of subjective refraction in most studies were close to 80 percent agreement within +/- 0.25D and 95 percent agreement within +/- 0.50D for spherical equivalent, sphere power, and cylinder power. The reliability of most autorefractors is similar to the reliability of conventional subjective refraction.The results of the reliability studies support Bannon's 1977 conclusion that conventional subjective refraction is reliable within 0.25 to 0.50D. Studies comparing objective autorefractors and conventional subjective refraction indicate that these autorefractors are satisfactory for a preliminary refraction but are not satisfactory as substitutes for conventional subjective refraction.