Purpose:

The aim of this study was to compare the reliability of different methods of objective refractive error measurement.

Material and Method:

Cycloplegic refractive errors of sixty-seven eyes of thirty-six male patients were measured. Subjects were chosen between the patients who had refractive errors more than 2.00 diopters of myopia, hyperopia or astigmatism. Spherical and cylindrical errors as well as spherical equivalents were measured with two different autorefractors and a retinoscope. Repeated measures analysis of variance and Tukey's multiple comparison test were used for the statistical analysis of refractive error measurements.

Results:

The mean and standard deviation values of spherical refractive error were 6.94±3.43 with retinoscopy, 7.21±3.29 for autorefractor 1, and 7.94±3.44 for autorefractor 2. The spherical equivalents were 7.50±3.43 for retinoscopy, 7.93±3.38 for autorefractor 1, and 8.83±3.64 for autorefractor 2. These values show that statistically and clinically significant differences existed between autorefractors 1 and 2 as well as between autorefractor 1 and retinoscope (p< 0.05).

Discussion:

The results of this study demonstrate that different measurement methods and instruments may yield different values of refractive errors, which may cause wrong decisions about the value of objective refraction. Standardization of measurement methods should be established to obtain valid, accurate and reliable results and, especially for occupational requirements, subjective refraction should gain wider acceptance as “gold standard” method. (Turk J Ophthalmol 2011; 41: 84-9)

Keywords: Refractive error, measurement, validity, reliability, accuracy