A Comparison of Autorefraction and Subjective Refraction in an Academic Optometry Clinic

Abstract

Background: Refractive error is the most common cause of decreased visual acuity. Refractive measurement in adults consists of cycloplegic (objective) and manifest (subjective) refraction. Although the effectiveness of autorefraction is a crucial factor, there needs to be more information on its accuracy and precision on each autorefractor compared with subjective measurement in Thai patients.

Objective: To compare the accuracy and precision of the two autorefractors' findings in Rajavithi Hospital, OptoChek Plus, and TOMEY Auto Refractometer RC-5000, with each other and with those of the subjective method.

Materials & methods: An observational study was conducted at the Ophthalmology clinic in Rajavithi Hospital from March 1, 2021, to March 31, 2022. All subjects were tested using the two autorefractors (OptoChek Plus and TOMEY Auto Refractometer RC-5000) and subjective refraction. One eye per subject was included in the study.

Results: Forty-eight patients (48 eyes) were enrolled in the study. The difference between spherical powers obtained by OptoChek and subjective refraction was not significantly different; however, there was a significant difference between those calculated by Tomey and the subjective method (p=0.77, p=0.04 respectively). The variations between cylindrical powers arrived at by the two autorefraction techniques and those calculated by the subjective method were significantly different (OptoChek and Tomey p-=0.01, p-value<0.001, respectively). In addition, 95% of the limit of agreement (95% of LOA) was low in the cylindrical measurement of each autorefractor compared with subjective refraction. (84.61%, 86.36%, respectively). No statistically significant difference between the spherical equivalent calculated by the two autorefractors and that of subjective refraction was observed in the present study (OptoChek: p-value=0.26 and Tomey: p-value=0.77).

Conclusions: There was a clinically significant difference between the cylindrical power calculated by the two autorefractors and those obtained from subjective refraction. Patients with high astigmatism should be monitored closely when measured by autorefractors, as there can be a slightly lower agreement between objective and subjective refraction.

Keywords: autorefraction; autorefractor; cylindrical power; refraction; spherical equivalent; spherical power; subjective refraction.

Figure 1. Bland–Altman Plots Evaluating the difference between measurements from each autorefractor and subjective refraction.*

* The agreement between subjective and autorefraction Sphere (A, B) for A: the OptoChek®, the lines indicate mean agreement (solid blue line at 0.026 Diopter) and the 95% limits of agreement (dashed red lines at -1.171 and 1.221 Diopter), and B: the Tomey, the lines indicate mean agreement (solid blue line at 0.161 Diopter) and the 95% limits of agreement (dashed red lines at -0.881 and 1.203 Diopter). Spherical equivalent (C, D) for C: OptoChek®, the lines indicate mean agreement (solid blue line at -0.157 Diopter) and the 95% limits of agreement (dashed red lines at -2.039 and 1.725 Diopter), and D: Tomey, the lines indicate mean agreement (solid blue line at 0.022 Diopter) and the 95% limits of agreement (dashed red lines at -0.979 and 1.023 Diopter). Cylinder (E, F) for E: OptoChek®, the lines indicate mean agreement (solid blue line at -0.192 Diopter) and the 95% limits of agreement (dashed red lines at -1.193 and 0.809 Diopter), and F: Tomey, the lines indicate mean agreement (solid blue line at -0.281 Diopter) and the 95% limits of agreement (dashed red lines at -0.717 and 0.155 Diopter).