title: Normal values for the size of a halo produced by a glare source.
abstract: OBJECTIVE
  To determine the size of a halo in the visual field induced by bright light in healthy eyes of all ages using the Vision Monitor (MonCv3; Metrovision, Pérenchies, France) and to assess the repeatability of the method.
  
  
  METHODS
  Measurements were made in the right eyes of 147 healthy subjects (mean age: 48.2 ± 16.2 years) who were classified into six age groups. Using the Vision Monitor, optotypes of low luminance were presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). The repeatability of the method was determined in a subset of 37 subjects older than 50 years by calculating the Bland-Altman coefficient of repeatability.
  
  
  RESULTS
  The mean radius of the halo was 111.6 ± 39.8 arc min. Halo radius started to increase significantly from the age of 50 to 59 years. The relationship between halo radius and age (r = 0.65; P < .0001) was described by fitting a power function to the data. Halo size was independent of gender. The coefficient of repeatability of the method was ±44 arc min.
  
  
  CONCLUSIONS
  Halo size increases with age following a power model. The normal halo size values provided could help clinicians distinguish between normal or abnormal glare problems. The intersession repeatability observed for halo size measurement indicates this method could be useful for assessing visual impairment caused by glare.
authors.affiliation: Faculty of Optics and Optometry, Complutense University, Madrid, Spain.
authors.forename: María C
authors.initials: MC
authors.lastname: Puell
authors.forename: María J
authors.initials: MJ
authors.lastname: Pérez-Carrasco
authors.forename: Ana
authors.initials: A
authors.lastname: Barrio
authors.forename: Beatriz
authors.initials: B
authors.lastname: Antona
authors.forename: Catalina
authors.initials: C
authors.lastname: Palomo-Alvarez
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D019466:Glare; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012160:Retina / Q000502:physiology*; D012542:Scattering, Radiation; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult