Refractive Error Changes at Near After Smartphone Use

To quantify short-timescale refractive recovery after a standardized smartphone near task and timed distance-viewing breaks aligned with the 20-20-20 paradigm, and to determine how much of the accommodative/near work-induced transient myopia (NITM) recovery occurs within the earliest seconds of a break.

In this cross-sectional, 58 students symptomatic for digital eye strain (Computer Vision Syndrome Questionnaire score ≥ 6) completed a 20-minute continuous reading task on smartphone. Objective refractive error was recorded with an open-field autorefractor at baseline, immediately post-task, and after distance-viewing breaks of 20 seconds, 1 minute, and 2 minutes (≥6 m fixation; no near work permitted).

The mean age of participants was 20.85±1.43 years. At baseline near fixation, mean sphere and SE were -2.08±0.45 and-2.38±0.46 D, respectively. Immediately after 20 minutes of reading, a myopic shift was evident (sphere -2.12±0.50 D; SE -2.47±0.46 D). During distance breaks, refractive measures recovered toward baseline in a biphasic pattern: A significant early recovery within 20 seconds (sphere P=0.007; SE P=0.005), followed by smaller improvements from 20 to 60 seconds (sphere P=0.266; SE P=0.034) and from 60 to 120 seconds (sphere P=0.415; SE P=0.270). Cylinder remained stable across conditions (≈ -0.6 D; P=0.136), whereas sphere and SE varied significantly across near and break intervals (both P<0.001).

After a 20-minute smartphone near task, the largest component of refractive recovery occurs within the first 20 seconds of distance fixation, with diminishing returns up to 2 minutes. This objective kinetics support the refocusing premise of the 20-20-20 approach and indicate that incorporating more frequent distance-viewing breaks can capture most accommodative/NITM recovery (20-2 min-20).