Purpose: Smartphone use is now ubiquitous and is associated with a range of ocular and visual symptoms. However, little is known about the etiology of the symptoms which accompany smartphone use and the relative contribution of accommodation/vergence versus that of the ocular surface and of blinking. This study examined the effects of 60 min reading on a smartphone on ocular symptoms, binocular vision, tear function, blinking and working distance.Methods: Twelve young adults (18-23 years; 9F:3M) with normal vision and without dry eye, or major accommodative/binocular vision disorders, completed this pilot study. Participants read a novel on a smartphone for 60 min and the following were measured before and after the reading task: eye strain and ocular surface symptoms, non-invasive tear break-up time (NIBUT), lipid layer appearance, tear meniscus height, horizontal fixation disparity, binocular accommodative facility. Spontaneous blink rate and amplitude were counted every 10 min, and viewing distance was measured at the same timepoints. Pre- and post-task comparisons were made using Wilcoxon signed-rank test and changes during the task were assessed using Friedman test. Associations were examined using Spearman's correlation.Results: Eyestrain symptoms and ocular surface symptoms increased after smartphone use, specifically comfort, tiredness and sleepiness items (p ≤ .02). Binocular accommodative facility decreased from a median of 11.3 (IQR 6.6) cycles/min pre-task to 7.8 (2.5) cycles/min post-task (p = .01), but there was no significant change in fixation disparity or working distance. There were no changes in NIBUT, lipid layer or tear meniscus height. Number of incomplete blinks per minute increased from a median of 6 blinks at 1 min to 15 at 60 min (p = .0049). Total blink rate (complete plus incomplete blinks) gradually increased over time, but this trend was not significant (p = .08). A greater increase in incomplete blinks over 60 min of reading was associated with worsening of the overall ocular surface symptoms score (ρ = -0.65, p = .02) and of the tiredness item (ρ = 0.70, p = .01).Conclusions: Extended use of smartphones appears to have important implications for ocular surface health and binocular function.
Keywords: Smartphone; accommodation; binocular vision; blink; digital device; ocular surface; ocular symptoms; tear function.