UC Irvine

Objective: Visual acuity (VA), the most common and simple measurement of visual function, is used worldwide in clinical practice and clinical research to quantify vision. However, rather than the full-letter width spacing standard on traditional visual acuity charts that might induce crowding, increased test-retest variability and bias, the visual acuity test on ColorDx is a single letter scoring, logMAR scaled and fast performed visual acuity measurement. The study aim is to study the reliability and validity of the visual acuity test on ColorDx on both healthy subjects and those with eye diseases.

Methods: This is a prospective comparative clinical study. A total of 54 participants subjects were enrolled with their right eyes. All subjects underwent test and retest visual acuity measurements at 4 meters using ColorDx and Early Treatment Diabetic Retinopathy Study (ETDRS) charts. All results were scored with logMAR units. Paired sample t-test, Pearson’s correlation and independent sample t-test were performed.

Results: The mean difference between the two visits of ColorDx was 0.03 ± 0.05 and that for ETDRS chart was 0.01 ± 0.03. None of the differences between the two visits were statistically significant (P>0.05). In Pearson correlation, r was 0.794 with a p-value less than 0.001. The mean differences between healthy and unhealthy groups were 0.23 for both tests. P-values were 0.03 and 0.01 of ETDRS chart and ColorDx, respectively.

Conclusion: The visual acuity test on ColorDx is a simple, reliable and standardized procedure for visual acuity measurement. The pilot data in our study provides preliminary evidence that it can be used as a valid alternative to ETDRS chart worldwide without the Latin alphabet barrier. The simple operation could be suitable for fast-paced clinical settings. More disease groups and larger sample size need to be evaluated in future studies.