Effect of Instrument Design and Technique on the Precision and Accuracy of Objective Refraction Measurement

Abstract

Background: To evaluate the precision and accuracy of objective refraction measurement obtained with combinations of instrument design and technique. We also compared the performance of the instruments with subjective refraction measurements. Method and analysis: The objective refraction was measured in 71 subjects with three autorefractometers that have different designs and measurement principles (binocular with fogging, binocular without fogging, and monocular with fogging). Repeatability and reproducibility metrics were calculated for the objective refraction measurements. The agreement of the objective refraction measurements between the three instruments and the agreement with the subjective refraction measurements were evaluated. Results: All three autorefractometers had repeatability and reproducibility limits smaller than 0.70D. The smallest difference (0.10D) in the spherical equivalent was seen between the two binocular instruments. Compared with the subjective refraction, the binocular without fogging technique had the smallest mean difference in spherical equivalent (<0.20D) whereas the binocular fogging technique had the smallest limit of agreement interval (1.00D). For all comparisons, the mean difference and limit of agreement interval for the cylindrical components were lower than 0.10D and 0.75D, respectively. Conclusion: All three instruments evaluated had good repeatability and reproducibility. The binocular fogging technique provided the best agreement with subjective refraction.

Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors?

“… 21 , 22 Repeatability also reflects the measurement technique's ability to discriminate one value of the given parameter from another – the higher the precision, the better the discriminant capability. 21 , 22 Although reports of accuracy and repeatability of autorefractors are available aplenty in the literature, 17 , 19 , 20 , 23 – 25 a systematic, comparative analyses of accuracy and repeatability across different autorefraction techniques obtained from the same cohort of subjects is not as readily available. Such an analysis will provide critical input on one technique's relative performance against others, enabling evidence-based justification of their utility as a starting point for subjective refraction in the clinic and as a screening tool for refractive errors in public health settings.…”

Effect of six different autorefractor designs on the precision and accuracy of refractive error measurement

“…We performed this measurement and waited 2 minutes to repeat it again. The previous autorefractor precision studies have analyzed the repeatability with either 2 or 3 repeated measurements [ 10 , 11 , 30 , 32 , 33 ]. As a supplementary evaluation to assess how the repeatability varies with 3 repeated measurements, we evaluated one of the autorefractor (NIII) on a subset of 16 subjects.…”

“…The pupil zone used for refraction measurement is also different in these methods. Previous studies have shown the objective refraction measurements obtained with different autorefractors vary, and it is suggested that this variation could be due to the measurement principle and design of each instrument [10][11][12][13][14]. The autorefractors are available as tabletop or handheld, and the clinical studies have shown that on average the differences among these two types of autorefractors are not clinically significant [12,15].…”

The Reliability and Acceptability of RDx-Based Tele-Controlled Subjective Refraction Compared with Traditional Subjective Refraction

“…As observed by Pei et al, 17 cycloplegic measurements are generally more positive or less negative than refractions without cycloplegia. Although enough fogging and standardized operations were performed to minimize the influences induced by accommodation, 31 this may not be enough for individuals with hyperopia or under the age of 10 years. 32 Hence, we urge caution and prudence when conducting tele-controlled subjective refraction on those patients.…”