title: Eye-related pain induced by visually demanding computer work.
abstract: OBJECTIVE
  Eye strain during visually demanding computer work may include glare and increased squinting. The latter may be related to elevated tension in the orbicularis oculi muscle and development of muscle pain. The aim of the study was to investigate the development of discomfort symptoms in relation to muscle activity and muscle blood flow in the orbicularis oculi muscle during computer work with visual strain.
  
  
  METHODS
  A group of healthy young adults with normal vision was randomly selected. Eye-related symptoms were recorded during a 2-h working session on a laptop. The participants were exposed to visual stressors such as glare and small font. Muscle load and blood flow were measured by electromyography and photoplethysmography, respectively.
  
  
  RESULTS
  During 2 h of visually demanding computer work, there was a significant increase in the following symptoms: eye-related pain and tiredness, blurred vision, itchiness, gritty eyes, photophobia, dry eyes, and tearing eyes. Muscle load in orbicularis oculi was significantly increased above baseline and stable at 1 to 1.5% maximal voluntary contraction during the working sessions. Orbicularis oculi muscle blood flow increased significantly during the first part of the working sessions before returning to baseline. There were significant positive correlations between eye-related tiredness and orbicularis oculi muscle load and eye-related pain and muscle blood flow. Subjects who developed eye-related pain showed elevated orbicularis oculi muscle blood flow during computer work, but no differences in muscle load, compared with subjects with minimal pain symptoms.
  
  
  CONCLUSIONS
  Eyestrain during visually demanding computer work is related to the orbicularis oculi muscle. Muscle pain development during demanding, low-force exercise is associated with increased muscle blood flow, possible secondary to different muscle activity pattern, and/or increased mental stress level in subjects experiencing pain compared with subjects with minimal pain.
authors.affiliation: Department of Optometry and Visual Science, Buskerud University College, Kongsberg, Norway. hannemt@hibu.no
authors.forename: Hanne-Mari Schiøtz
authors.initials: HM
authors.lastname: Thorud
authors.forename: Magne
authors.initials: M
authors.lastname: Helland
authors.forename: Arne
authors.initials: A
authors.lastname: Aarås
authors.forename: Tor Martin
authors.initials: TM
authors.lastname: Kvikstad
authors.forename: Lars Göran
authors.initials: LG
authors.lastname: Lindberg
authors.forename: Gunnar
authors.initials: G
authors.lastname: Horgen
mesh_terms: D000328:Adult; D001248:Asthenopia / Q000209:etiology / Q000503:physiopathology*; D001292:Attitude to Computers; D003201:Computers; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000503:physiopathology*; D009801:Oculomotor Muscles / Q000098:blood supply / Q000503:physiopathology*; D010146:Pain / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D010147:Pain Measurement; D017156:Photoplethysmography; D012016:Reference Values; D012039:Regional Blood Flow; D012720:Severity of Illness Index; D055815:Young Adult