Longitudinal pilot study on 12 young healthy adults comparing effects of smartphone use over a 60-minute period. Reading conditions and smartphone use was standardised for all participants. Ocular symptoms, tear function and binocular vision were assessed before and after each task. Eyestrain Symptoms Questionnaire (ESQ) and Numerical Rating Scale (NRS) were completed. Total ESQ and NRS scores were significantly worse after 60 minutes of reading on the smartphone, with tiredness and comfort being the worst of all the categories. Tear film variables (such as lipid layer integrity and tear meniscus height) were unchanged, however, measurements were taken 15 minutes after the task was completed, and so short-term changes would not have been detected. There was an increase in the rate of incomplete blinks over the time period, associated with worsening of ocular surface symptoms score and symptom of tiredness. A previous study showed that reduced blink amplitude (incomplete blinking) is a marker of general fatigue. Binocular accommodative facility was significantly reduced post-task. However, this could be influenced by vergence ability, so the authors acknowledge that future studies should include vergence testing as well as monocular and binocular accommodative testing.