Blink rate measured in situ decreases while reading from printed text or digital devices, regardless of task duration, complexity or working distance

PurposeTo compare blinking measured in situ during various tasks and examine relationships with ocular surface symptoms. Day-to-day repeatability of blink rate and interblink interval was assessed. MethodsTwenty-four students (28.6{+/-}6.3 years; 8M:16F) completed six reading tasks (printed text, laptop, TV, smartphone, smartphone at 50% brightness, smartphone with complex text), and two non-reading tasks (conversation, walking) in a randomised cross-over study. Ocular surface symptoms and clinical signs were assessed. Blink rate and interblink interval were measured using a wearable eye tracking headset. Blink parameters were compared across tasks and time (linear mixed model and post hoc comparisons with Bonferroni correction). Associations between blinking, symptoms, ocular surface, and clinical signs were assessed (Spearmans correlation). The smartphone reading task was completed twice to determine coefficient of repeatability. ResultsBlink rate was lower (mean 10.7{+/-}9.7 blinks/min) and interblink interval longer (mean 9.6{+/-}8.7s) during all reading tasks compared to conversation (mean 32.4{+/-}12.4 blinks/min; 1.5{+/-}0.6s) and walking (mean 31.3{+/-}15.5 blinks/min; 1.9{+/-}1.3s) (p<0.001). There were no significant differences in blink parameters between any of the reading tasks, nor between conversation and walking. Changes in blinking occurred within one minute of starting the task. No associations were evident between blink rate or interblink interval and ocular surface symptoms or signs. Coefficient of repeatability was {+/-}12.4 blinks/min for blink rate and {+/-}18.8s for interblink interval. ConclusionSpontaneous blinking can be reliably measured in situ. Blink rate was reduced and interblink interval increased during reading compared to conversation and walking. Changes in blinking were immediate and sustained, and not associated with ocular surface symptoms or signs.