Timing of Digital Device Exposure as a Source of Measurement Error in Dry Eye Disease Research: A Critical Narrative Review.

Dry eye disease (DED) is a common, multifactorial disorder of the ocular surface, and rising digital device use is increasingly recognised as a modifiable contributor. Digital eye strain (DES), a related but distinct symptom construct that also encompasses uncorrected refractive error and binocular vision anomalies, is reported in 50-90% of regular device users, compared with 5-50% for DED itself depending on diagnostic criteria; these figures should not be conflated. Reduced blink rate during screen viewing appears driven substantially by cognitive task demand rather than the screen itself, since a controlled comparison of matched digital and hard-copy reading found no difference in blink rate between formats. Incomplete blinking, however, was higher with the digital device and is independently associated with dry eye signs and symptoms in cross-sectional data, though that data did not measure device exposure and cannot establish that screen use causes the incomplete blinking seen in habitual users. No additional effect of contact lens wear on screen-related dryness was detected in one experimental study using 20-minute exposures; this is not evidence of no effect. Behavioural interventions, including the 20-20-20 rule, and oral omega-3 carry only low-certainty evidence, and a large randomised trial found omega-3 ineffective for dry eye more broadly. The 2023 Tear Film and Ocular Surface Society (TFOS) Lifestyle report comprehensively reviewed this literature and identified an unanswered question: no study has systematically tracked how ocular surface measurements change over time after digital device exposure ends. This review takes that gap as its focus. It argues that recent, unstandardised device exposure before ocular surface testing is a source of measurement error that has not been controlled for across the dry eye literature, examines the evidence for this effect, and proposes a research design and, informed by imaging tools that have become available since 2022, a feasible way to close the gap.