title: Monocular and binocular reading performance in subjects with normal binocular vision.
abstract: BACKGROUND
  It is well known that problems with binocular vision can cause issues for reading; less known is to what extent binocular vision improves reading performance. The purpose of this study was to explore the role of binocularity by directly comparing monocular and binocular reading in subjects with typical reading skills and normal binocular vision. A secondary purpose was to assess any asymmetry in monocular performance and its association with the sighting dominant eye.
  
  
  METHODS
  In a balanced repeated measures experiment, 18 subjects read paragraphs of text under monocular and binocular conditions. All subjects went through an optometric examination before inclusion. Reading speed and eye movements were recorded with an eye tracker.
  
  
  RESULTS
  The mean difference in reading speed (2.1 per cent) between monocular (dominant and non-dominant eye averaged) and binocular reading speed was not significant. A significant difference in reading speed was found between binocular and the non-dominant eye, as determined by the far sighting test (p = 0.03). Monocular reading showed significantly increased (8.9 per cent) fixation duration (p < 0.01) and longer regressive saccades by 0.43 character spaces (p < 0.01). Reading with the non-dominant eye, as determined by the near sighting test, showed increased progressive saccade length by 0.2 characters compared to the dominant eye (p = 0.03). No other significant differences between dominant and non-dominant eyes were found. The agreement between the faster reading eye and ocular dominance was 44 to 56 per cent depending on whether dominance was determined at near or far.
  
  
  CONCLUSIONS
  The outcomes suggest that in subjects with normal binocular vision, there is no marked enhancement in reading performance by binocular vision when reading paragraphs of text. Furthermore, the monocular reading performance appears to be close to equal and any small differences in performance appear not to be strongly associated with ocular dominance.
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden. jan.johansson.1@ki.se.
authors.forename: Jan
authors.initials: J
authors.lastname: Johansson
authors.forename: Tony
authors.initials: T
authors.lastname: Pansell
authors.forename: Jan
authors.initials: J
authors.lastname: Ygge
authors.forename: Gustaf Öqvist
authors.initials: GÖ
authors.lastname: Seimyr
mesh_terms: D000328:Adult; D023882:Dominance, Ocular / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011932:Reading; D012016:Reference Values; D015348:Vision, Binocular / Q000502:physiology*; D014792:Visual Acuity; D055815:Young Adult
keywords: binocular; eye movements; monocular; ocular dominance; reading; reading speed; sighting dominance