A novel method to measure margin reflex distance using the autorefractometer

To determine the margin reflex distance (MRD) in healthy subjects using autorefractometer front monitor images (ARFMI) and validate the accuracy of this method by comparing it with conventional methods.

One hundred eyes of 50 healthy subjects aged 20-59 years were included in the study. Autorefractometer front monitor images were video-recorded using a smartphone camera, and screenshots were taken to analyze the MRD. The results were compared with those from conventional methods to determine the reliability of the method. To evaluate the repeatability and reproducibility of all measurement methods, we performed two different visits by two observers.

The mean MRD-1 of the autorefractometer image measurement was 4.29 ± 0.90 mm, mean MRD-1 of the of the digital photography image measurement was 3.78 ± 1.03 mm, and mean MRD-1 of the manual measurement was 4.02 ± 1.09 mm. The mean difference (MD) of MRD-1 was analyzed and it was found that MD of the autorefractometer image was significantly higher than the MD of other groups (p < 0.001). The best repeatability was found in the autorefractometer image measurement [intraclass correlation coefficients (ICC): 0.960], and substantial to excellent repeatability was found in the manual (ICC: 0.903) and digital photography image measurements (ICC: 0.843). The mean inter-eye difference of MRD-1 measured by the three methods was analyzed, and there was a statistically significant difference in the autorefractometer and digital image groups (p: 0.001, p: 0.002, respectively).

Margin reflex distance measurement using ARFMI analysis is a novel, simple, accurate, reliable, and objective method. The autorefractometer device is readily available and can be found in any ophthalmic clinic. Therefore, ophthalmologists can easily measure and record MRD values and use the accurate and reliable results for follow-up and medicolegal issues.