Abstract
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.
Highlights
Testing visual acuity (VA) is one of the most sensitive ways of monitoring the functioning of the visual system (Levenson & Kozarsky 1990), it is vital to ensure any chart used to measure VA is accurate and repeatable
Yu et al (2014) tested smartphone-based electronic visual acuity (SEVA) technology on patients with a range of VAs and ocular pathologies and found it highly correlated to the ETDRS chart and near LEA numbers test with no significant difference between the VA scores achieved
Perera et al (2015) found that the Snellen iPhone app gave no significant difference in mean VA scores compared to the Snellen chart, the largest difference of nearly three lines was recorded when VA was worse than 6/18 Snellen
Summary
Testing visual acuity (VA) is one of the most sensitive ways of monitoring the functioning of the visual system (Levenson & Kozarsky 1990), it is vital to ensure any chart used to measure VA is accurate and repeatable. To provide more standardisation and accuracy in the scoring process the logMAR Bailey-Lovie chart was developed using a family of 10 non-serif letters (Bailey & Lovie 1976). The Early Treatment Diabetic Retinopathy Study used the same logMAR chart design principles but a family of 10 Sloan letters to develop the ETDRS chart (Kassoff 1979) which is considered the gold-standard chart for VA testing (Kalpana, Karthick & Jayarajini 2013). Yu et al (2014) tested smartphone-based electronic visual acuity (SEVA) technology on patients with a range of VAs and ocular pathologies and found it highly correlated to the ETDRS chart and near LEA numbers test with no significant difference between the VA scores achieved. Perera et al (2015) found that the Snellen iPhone app gave no significant difference in mean VA scores compared to the Snellen chart, the largest difference of nearly three lines was recorded when VA was worse than 6/18 Snellen
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