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Conor Patrick Malone, Colm McCourt, Nawal T Al Daqqaq, Conor Murphy; Evaluation of Tablet Computers in the Assessment of Visual Acuity: Can iPads™ Replace the Snellen Chart?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5599.
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© ARVO (1962-2015); The Authors (2016-present)
Assessment of visual acuity (VA) is an essential clinical examination in ophthalmology and across many other specialties. In the community, primary care physicians use VA to assist in triaging patients for referral to ophthalmology. The advent of tablet computers presents an opportunity to offer physicians access to inexpensive, standardised, and accurate methods of measuring VA. Previous studies have found that glare and low baseline VA limit the reliability of tablet computers in assessing VA. This study seeks to assess the accuracy of a popular tablet application used for measuring VA and to examine the effects of decreased luminance on test validity.
79 ambulatory care patients were recruited from a large national ophthalmology tertiary referral centre. Each patient's VA was tested twice: firstly using the established Lighthouse vision chart and secondly on an Apple iPad 2™ tablet using proprietary Kybervision Visual Acuity XL software. Phase 1 used a luminance setting of 380 cd/m2. Phase 2 used a lower luminance of 160 cd/m2. Phase 1 included 88 eyes of 46 patients. Phase 2 included 61 eyes of 33 patients. VA was recorded on the LogMAR scale.
In Phase 1, at maximum device luminance of 380 cd/m2, there was a statistically significant difference between the standard chart and the tablet device for both unaided VA (p=0.0028) and best-corrected VA (p=0.0003). In Phase 2, at moderate luminance of 160 cd/m2, no statistically significant difference was found between measurements on the Lighthouse and iPad charts for either unaided VA (p=0.1008) or best-corrected VA (p=0.2849).
Previous studies have sought to validate the use of tablet devices for measurement of VA, but have cited glare and poor baseline VA as limiting factors. These outcomes were confirmed by Phase 1 of this study. ETDRS protocol recommends that luminance in VA assessment should be set between 80 and 320 cd/m2. Phase 2 of this study demonstrated that the use of moderate luminance (160 cd/m2) validates the use of this tablet computer and software application as an equal alternative to traditional printed or projected vision charts.
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