Your threshold for clear evidence may vary. I found several studies, including an attempt at a randomized trial measuring the effects of screen use on the optic

Your threshold for clear evidence may vary. I found several studies, including an attempt at a randomized trial measuring the effects of screen use on the optical surface: http://doi.org/10.1111/cts.12933 http://doi.org/10.1111/cts.12933 "Effects on the Ocular Surface from Reading on Different Smartphone Screens", Yuan, K. et al, 2020 A few other studies found differing effects on blink rate and visual fatigue from different screens. http://doi.org/10.1097/OPX.0000000000001616 http://doi.org/10.1097/OPX.0000000000001616 "How do Different Digital Displays Affect the Ocular Surface", Talens-Estarelles, C. et al, 2020 In this case, screen size was also associated with detrimental effects, with larger screens generally performing worse, and smartphones similar in effect to the e-reader. This may partially account for some hitherto unexplained preference for smartphones over computers among some users. The e-reader was better than the tablet, but not better than the smartphone. The earliest study to show any effect was Benedetto et al, focusing on visual fatigue, which has been widely cited: http://doi.org/10.1371/journal.pone.0083676 http://doi.org/10.1371/journal.pone.0083676 "E-Readers and Visual Fatigue", Benedetto, S. et al, 2013. At least one study found statistically insignificant effects, though the e-reader showed mostly improved (but insignificant) test results, which does not weigh against the existence of an effect: http://doi.org/10.1111/j.1475-1313.2012.00928.x http://doi.org/10.1111/j.1475-1313.2012.00928.x "Reading on LCD vs e-Ink displays: effects on fatigue and visual strain", Siegenthaler, E. et al, 2012. Siegenthaler et al do not measure effects on the ocular surface; such effects seem to have reached scientific interest only in the late 2010s. Also, the difference between e-Ink and LCD peak luminance in Siegenthaler was only 10%; the ratio of ambient to screen luminance has been observed to mediate the relationship between screen usage and eye strain: http://doi.org/10.1016/j.displa.2020.101943 http://doi.org/10.1016/j.displa.2020.101943 "Influence of ambient-tablet PC luminance ratio on visual fatigue", Yu, H. and Akita, T. 2020. While I attempted to find any high-quality studies, positive or negative, available looking at the relationship between screen type and eye strain, my interpretation of the data likely reflects (hah!) my strong intuition that shining a light directly into your eyes is bad.