title: Visual discomfort while watching stereoscopic three-dimensional movies at the cinema.
abstract: OBJECTIVE
  This study investigates discomfort symptoms while watching Stereoscopic three-dimensional (S3D) movies in the 'real' condition of a cinema. In particular, it had two main objectives: to evaluate the presence and nature of visual discomfort while watching S3D movies, and to compare visual symptoms during S3D and 2D viewing.
  
  
  METHODS
  Cinema spectators of S3D or 2D films were interviewed by questionnaire at the theatre exit of different multiplex cinemas immediately after viewing a movie.
  
  
  RESULTS
  A total of 854 subjects were interviewed (mean age 23.7 ± 10.9 years; range 8-81 years; 392 females and 462 males). Five hundred and ninety-nine of them viewed different S3D movies, and 255 subjects viewed a 2D version of a film seen in S3D by 251 subjects from the S3D group for a between-subjects design for that comparison. Exploratory factor analysis revealed two factors underlying symptoms: External Symptoms Factors (ESF) with a mean ± S.D. symptom score of 1.51 ± 0.58 comprised of eye burning, eye ache, eye strain, eye irritation and tearing; and Internal Symptoms Factors (ISF) with a mean ± S.D. symptom score of 1.38 ± 0.51 comprised of blur, double vision, headache, dizziness and nausea. ISF and ESF were significantly correlated (Spearman r = 0.55; p = 0.001) but with external symptoms significantly higher than internal ones (Wilcoxon Signed-ranks test; p = 0.001). The age of participants did not significantly affect symptoms. However, females had higher scores than males for both ESF and ISF, and myopes had higher ISF scores than hyperopes. Newly released movies provided lower ESF scores than older movies, while the seat position of spectators had minimal effect. Symptoms while viewing S3D movies were significantly and negatively correlated to the duration of wearing S3D glasses. Kruskal-Wallis results showed that symptoms were significantly greater for S3D compared to those of 2D movies, both for ISF (p = 0.001) and for ESF (p = 0.001).
  
  
  CONCLUSIONS
  In short, the analysis of the symptoms experienced by S3D movie spectators based on retrospective visual comfort assessments, showed a higher level of external symptoms (eye burning, eye ache, tearing, etc.) when compared to the internal ones that are typically more perceptual (blurred vision, double vision, headache, etc.). Furthermore, spectators of S3D movies reported statistically higher symptoms when compared to 2D spectators.
authors: Optics and Optometry, Department of Sciences, Roma Tre University, Rome, Italy.
authors: Fabrizio
authors: F
authors: Zeri
authors: Stefano
authors: S
authors: Livi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001248:Asthenopia / Q000209:etiology* / Q000503:physiopathology; D002648:Child; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009040:Motion Pictures; D012030:Refractive Errors / Q000150:complications / Q000628:therapy; D012307:Risk Factors; D012720:Severity of Illness Index; D055815:Young Adult
keywords: 2D movie; stereoscopic three-dimensional movie; visual discomfort; visual symptoms