title: Interactions of visual and cognitive stress.
abstract: BACKGROUND
  The objective of this research is to assess the ocular and muscular response to long-duration reading under different visual and cognitive difficulty levels.
  
  
  METHODS
  Thirty-five subjects, with 20/20 vision and without history of ocular pathology or cognitive deficits, participated in the study. Subjects read under different visual and cognitive difficulty levels for 6 (30-minute) conditions. Upper and lower orbicularis oculi, frontalis, and trapezius muscle activities were recorded using surface electromyography (EMG). Aperture size, pupil diameter, and pulse rate of the subjects were recorded with a video camera, pulse meter, and ISCAN eye tracker (ISCAN Inc.), respectively.
  
  
  RESULTS
  The results show that the texts read with a refractive error caused increased orbicularis oculi EMG power and reduced aperture size (P < 0.001). There was no statistically significant difference between the conditions for pulse rate, pupil diameter, or EMG activity of the frontalis and trapezius muscles with either visual or cognitive stress presented in this experiment.
  
  
  CONCLUSIONS
  Visual stress experienced due to reading under an induced refractive error is potentially mediated by a local mechanism, different from the mechanism underlying reading under low contrast or high cognitive demand.
authors: The Ohio State University, College of Optometry, Columbus, USA. Nahar.2@osu.edu
authors: Niru K
authors: NK
authors: Nahar
authors: Sowjanya
authors: S
authors: Gowrisankaran
authors: John R
authors: JR
authors: Hayes
authors: James E
authors: JE
authors: Sheedy
mesh_terms: D000293:Adolescent; D001248:Asthenopia / Q000209:etiology / Q000503:physiopathology*; D003071:Cognition / Q000502:physiology*; D018450:Disease Progression; D004576:Electromyography; D005133:Eye Movements / Q000502:physiology*; D005152:Facial Muscles / Q000503:physiopathology; D005500:Follow-Up Studies; D006801:Humans; D009801:Oculomotor Muscles / Q000503:physiopathology*; D011932:Reading; D013312:Stress, Physiological / Q000502:physiology*; D013315:Stress, Psychological / Q000150:complications / Q000503:physiopathology*; D014741:Video Recording; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult