Does the EyeChart App for iPhones Give Comparable Measurements to Traditional Visual Acuity Charts?

Aim: To investigate if the EyeChart app gives accurate visual acuity (VA) measurements that are comparable to those achieved using traditional VA charts.

Method: Twenty-four participants (aged 18-27 years, mean 20.13 ± 1.78 years) with VA of 6/60 Snellen or better regardless of any strabismus, amblyopia, or ocular pathology volunteered for this prospective study. The best-corrected monocular VA of each participant's right eye was measured on the Snellen chart at 6 m, the ETDRS chart at 3 m, and the EyeChart app presented on an iPhone SE at 1.2 m (4ft).

Results: The mean VA scores obtained were: -0.13 ± 0.08 logMAR on the Snellen chart, -0.11 ± 0.08 logMAR on the ETDRS chart, and -0.09 ± 0.07 logMAR on the EyeChart app. After Bonferroni Correction adjustments were applied, a significant difference was found between the EyeChart app and the Snellen chart (t = -3.756, p = 0.003), however the difference between the EyeChart app and the ETDRS chart did not reach statistical significance (t = -2.391, p = 0.076). The EyeChart app had a strong correlation with both the Snellen (r = 0.79, p < 0.01) and ETDRS charts (r = 0.88, p < 0.01). The Coefficients of Agreement revealed a variation of less than one logMAR line between the EyeChart app and the traditional VA charts (Snellen: 0.09 logMAR; ETDRS: 0.08 logMAR).

Conclusion: This study found that the EyeChart app gives accurate VA scores that are comparable to those achieved using the gold-standard ETDRS chart in a healthy young adult population. However, the accuracy and repeatability of the EyeChart app when testing a patient population must be investigated before it can be integrated into clinical practice.