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Refractive Error Changes at Near After Smartphone Use
Taghi Naghdi1, Haleh Kangari1, Alireza Akbarzadeh Baghban2, Masoud Khorrami-Nejad31Department of Optometry, School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran2Proteomics Research Center, Department of Biostatistics, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3Department of Optometry, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran
OBJECTIVES: 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.
METHODS: 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).
RESULTS: 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).
DISCUSSION AND CONCLUSION: 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).
Keywords: Accommodation, digital eye strain, near work-induced transient myopia, open-field autorefractor, 20-20-20 rule
Manuscript Language: English
