Validation of the visual acuity iPad app Eye Chart Pro compared to the standard Early Treatment Diabetic Retinopathy Study chart in a low-vision population

• Published in: Journal of telemedicine and telecare 2022-10, Vol.28 (9), p.680-686
• Main Authors: Hazari, Hassan, Curtis, Rachel, Eden, Karen, Hopman, Wilma M, Irrcher, Isabella, Bona, Mark D
• Format: Article
• Language: English
• Subjects: Diabetes; Diabetic retinopathy; Telemedicine; Visual acuity
• ISSN: 1357-633X; 1758-1109
• DOI: 10.1177/1357633X20960640

Introduction A low-vision assessment (LVA) is central to developing a vision rehabilitation plan. However, access to LVAs is often limited by the quantity and geographic distribution of low-vision providers, as well as patient-centred transportation challenges. A tablet-based LVA tool kit, delivered virtually, has the potential to overcome many of these barriers. The purpose of this research was to validate a key component of the tablet-based tool kit – a commercially available iPad visual acuity (VA) test (Eye Chart Pro) iPad app – in a low-vision population. Methods Participants with low vision (n = 26) and those who were normally sighted (n = 25) underwent VA testing with both the iPad VA test application and the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. The VA data were compared using a t-test, linear regression and Bland–Altman analysis. Results There was no significant difference in the mean absolute difference in VA (log of minimum angle of resolution (logMAR)=0.11; p = 0.82). Eye Chart Pro and Standard ETDRS Chart measures were also not significantly different (p = 0.98). However, there were significant differences between test methods in the low-vision group and the normally sighted group (p > 0.0001 and p = 0.007, respectively). The Bland–Altman analysis showed a mean bias (difference) of –0.0005 logMAR between methods, and 95% limits of agreement of 0.298 and –0.299 logMAR. Discussion The ETDRS chart function on the Eye Chart Pro application can reliably measure VA across a range, from normally sighted patients to those with low vision.