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Validation of the visual acuity iPad app Eye Chart Pro compared to the standard Early Treatment Diabetic Retinopathy
Hassan Hazari1, Rachel Curtis1, Karen Eden1
1Department of Ophthalmology, Queen's University and Hotel Dieu Hospital, Canada.
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.
