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

Purpose To 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. Methods Twenty-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 (Spearman’s correlation). The smartphone reading task was completed twice to determine coefficient of repeatability. Results Blink 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. Conclusion Spontaneous 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research did not receive specific funding from agencies in the public, commercial, or not-for-profit sectors. The first author, NC received a UNSW Tuition Fee Remission Postgraduate Research Scholarship and the Australian Government Research Training Program Thesis Completion Scholarship. The research was also supported by the Dorothy Carlborg Research Grant from the Cornea and Contact Lens Society of Australia, and the UNSW Faculty of Science Research Infrastructure Scheme. The funding sources have no involvement in the study design, conduct of the research, collection, analysis and interpretation of data, writing of the report, preparation of the article or in the decision to submit the article for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Approval was obtained from the UNSW Sydney Human Research Ethics Advisory Panel I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The datasets generated during and/or analysed during the current study are available in the Mendeley Data repository