Justin Cooper , 2025-04-18 15:34:00
April 18, 2025
2 min read
Key takeaways:
- Digital eyestrain symptoms were greatest with a cognitively demanding task on a screen and least with a less demanding task on paper.
- Working distance decreased over time across all tasks.
Working distance decreased significantly over the course of 30-minute reading tasks on both paper and a screen, but digital eyestrain symptoms were instead linked to cognitive demand and the mode of presentation, according to a study.
“[Digital eyestrain], also known as computer vision syndrome, has been associated with a wide range of symptoms, with no definitive cause identified to date,” Elianna Sharvit, OD, MS, and Mark Rosenfield, MCOptom, PhD, FAAO, Dipl AAO, both of SUNY College of Optometry, wrote in Optometry and Vision Science.
Working distance decreased significantly over the course of 30-minute reading tasks on both paper and a screen, but digital eyestrain symptoms were instead linked to cognitive demand and the mode of presentation. Image: Adobe Stock
“Several investigations have reported that symptoms of eyestrain are worse when comparing the same reading or near task performed on paper vs. a digital screen,” they wrote. “Cognitive demand or load, otherwise known as the mental difficulty of a task, has also been associated with symptoms of digital eyestrain, although the mechanism linking the two has not been elucidated.”
Sharvit and Rosenfield conducted a study to learn more about how digital eyestrain symptoms correlated with working distance, cognitive demand and use of paper vs. a tablet screen. They recruited 30 students from SUNY College of Optometry (mean age, 24 years; 87% women), each of whom completed four 30-minute reading tasks:
- Reading random words from an Apple iPad and identifying those beginning with a specific letter (considered to be “cognitively demanding”).
- Reading a children’s story (Alice’s Adventures in Wonderland) on the same iPad (considered to be “less cognitively demanding”).
- The same task as the first but using printed paper instead of an iPad.
- The same task as the second but using printed paper instead of an iPad.
In each task, the iPad or paper was placed on a clipboard “so that the overall size and weight of the material would be as similar as possible,” the researchers wrote. The study participants could hold the reading material at any comfortable distance, but they were instructed to hold the clipboard upright and keep their chin pointed at the reading material.
Working distance was measured with a Clouclip device mounted to participants’ spectacles or spectacles with no lenses for those who did not wear glasses. The participants completed a symptom questionnaire immediately before and after each task.
All four tasks led to statistically significant increases in patient-reported digital eyestrain symptoms. However, the increase in symptoms was greatest with the cognitively demanding task on an iPad (median score change: 11) and lowest with the less cognitively demanding task on paper (median score change: 3.5), according to an analysis of variance.
When averaged across all four tasks, working distance decreased significantly within the first 10 minutes and then remained stable. However, working distance led to no significant change in symptom score in either univariate or multivariate mixed-effect linear regression models.
The findings indicate “that the increase in symptoms seen with more cognitively demanding tasks on the tablet computer was not related to a change in working distance,” Sharvit and Rosenfield wrote.
“Future investigations should seek to evaluate why cognitively demanding tasks performed on a tablet computer induced more subjective symptoms of digital eyestrain,” they said. “To explore this, objective testing of visual function (such as accommodative lag and ocular alignment), as well as assessment of the anterior surface of the eye and tear film, both during and after the task, could be used to determine whether the symptoms are truly visual in origin or rather if the perceived difficulty of the task is related to the development of symptoms on a psychological basis.”