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Oren Yehezkel, Anna Sterkin, Maria Lev, Uri Polat; Digital precise remote near visual acuity evaluation using mobile devices. Invest. Ophthalmol. Vis. Sci. 2013;54(15):582. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Our aim was to develop a tool for precise remote self-assessment of near visual acuity in order to accurately and remotely estimate the functional reading acuity.
We used an application by Ucansi Inc., developed for iOS-based mobile devices (iPhone, iPad, iPod), based on the technology tested both on mobile devices and PCs (electronic visual acuity, eVA). Here we present part of the data, collected on 73 volunteers that were tested on iPhone 4, operating the application by themselves. The minimal measurable acuity is -0.18 logMAR, as determined by the pixel size of 0.078 mm. The stimuli were matrices composed of 25 letters "E" (5×5), each with a randomly chosen orientation out of 4 possibilities (left, right, up or down). Two variations of inter-letter spacing within the matrix were used (0.4 and 1 letter size). The task was to report the orientation of the central letter. The evaluation was performed using a staircase measuring the minimal detectable target size. For each staircase, the duration of target presentation (ranging between 240 to 30 msec) and the inter-letter spacing were changed. The results were compared to the standard clinical near visual acuity chart (ETDRS chart-based visual acuity, cVA) and to the required reading addition (measured using the fused cross-cylinder test, FCC).
There was a significant correlation between the eVA and the cVA. Best correlation was found between monocular eVA and cVA (R=0.85, p<0.01; eVA: mean of 0.34±0.02 logMar, ranging between -0.09 and 0.73; mean of 0.32±0.02; cVA: ranging between -0.04 and 0.72). There was also a significant correlation with the FCC measurement (R=0.73, p<0.01; mean of 1.58±0.07, ranging between 0 and 2.75).
The remote self-assessment of near visual acuity using the iOS-based application is very accurate and may better predict the functional visual acuity due to the brief stimuli presentation similar in duration to a single fixation between saccades during reading. Moreover, measurements under the conditions of letter crowding induced by the letter matrix used by the application better estimate the functional reading acuity as opposed to single letter detection used in reading chart measurements. The assessment may be performed both monocularly and binocularly. Finally, VA improvement measured with eVA was highly correlated to the improvement measured by cVA.
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