Evaluation of visual acuity measurements after autorefraction vs manual refraction in eyes with and without diabetic macular edema

Abstract

Objective: To compare visual acuity (VA) scores after autorefraction vs manual refraction in eyes of patients with diabetes mellitus and a wide range of VAs.

Methods: The letter score from the Electronic Visual Acuity (EVA) test from the electronic Early Treatment Diabetic Retinopathy Study was measured after autorefraction (AR-EVA score) and after manual refraction (MR-EVA score), which is the research protocol of the Diabetic Retinopathy Clinical Research Network. Testing order was randomized, study participants and VA examiners were masked to refraction source, and a second EVA test using an identical supplemental manual refraction (MR-EVAsuppl score) was performed to determine test-retest variability.

Results: In 878 eyes of 456 study participants, the median MR-EVA score was 74 (Snellen equivalent, approximately 20/32). The spherical equivalent was often similar for manual refraction and autorefraction (median difference, 0.00; 5th-95th percentile range, -1.75 to 1.13 diopters). However, on average, the MR-EVA scores were slightly better than the AR-EVA scores, across the entire VA range. Furthermore, the variability between the AR-EVA scores and the MR-EVA scores was substantially greater than the test-retest variability of the MR-EVA scores (P < .001). The variability of differences was highly dependent on the autorefractor model.

Conclusions: Across a wide range of VAs at multiple sites using a variety of autorefractors, VA measurements tend to be worse with autorefraction than manual refraction. Differences between individual autorefractor models were identified. However, even among autorefractor models that compare most favorably with manual refraction, VA variability between autorefraction and manual refraction is higher than the test-retest variability of manual refraction. The results suggest that, with current instruments, autorefraction is not an acceptable substitute for manual refraction for most clinical trials with primary outcomes dependent on best-corrected VA.

Figure 1A

Flowchart of Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test Testing for Study Participants Participating in Another Diabetic Retinopathy Clinical Research Network Protocol.

Figure 1B

Flowchart of Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Testing for Study Participants not Participating in Another Diabetic Retinopathy Clinical Research Network Protocol

Figure 2

Bland-Altman Plot of Difference between Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Tests Measured Using Manual Refraction Solid reference line indicates median; dashed lines indicate 5^th and 95^th percentiles MR-EVA= Manual refraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score; MR-EVAsupl= Supplemental Manual refraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score

Figure 3

Bland-Altman Plot of Difference between Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Tests Measured Using Manual Refraction and Auto Refraction Solid reference line indicates median; dashed lines indicate 5^th and 95^th percentiles MR-EVA=Manual refraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score; AR-EVA= Autorefraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score.

Figure 4

Bland-Altman Plot of Difference between Early Electronic Treatment Diabetic Retinopathy Study Visual Acuity Tests Measured Using Manual Refraction and Auto Refraction by Topcon 8000 Series Machines Solid reference line indicates median; dashed lines indicate 5^th and 95^th percentiles MR-EVA= Manual refraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score; AR-EVA= Autorefraction Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test letter score.