title: Changes in the objective amplitude of accommodation with pupil size.
abstract: OBJECTIVE
  We evaluate the effect of pupil size on objectively measured amplitude of accommodation (AA).
  
  
  METHODS
  Pupil diameter and wavefront aberrometry were obtained in 15 eyes when stimulus swept across the range of clear vision in steps of 0.5 diopters. Wavefront refraction techniques were used to compute objective AA as the maximum refractive change. Measurements were obtained monocularly under low and high ambient room lighting conditions with a fixed luminance of the fixation target. Amplitude of accommodation computations were performed taking into account just paraxial rays (paraxial AA) or including the effects of the change of spherical aberration during accommodation (minRMS AA).
  
  
  RESULTS
  Mean pupil size values at low light level were 6.26 mm (relaxed) and 4.15 mm (maximum accommodation), whereas at the high light level, those values became 4.74 and 3.04 mm, respectively. The effects of both light level on accommodation were significant (p < 0.001), and accommodative miosis was slightly larger at low light levels. Mean minRMS and paraxial AA were always greater by more than 1 diopter in high than in low ambient lighting conditions (p < 0.01), indicating a significant impact of pupil size on AA.
  
  
  CONCLUSIONS
  The influence of the ambient lighting on the objective AA is not only attributed to the increased effects of spherical aberration as the pupil dilates but mostly attributed to a decrease in the paraxial accommodation as pupil dilates.
authors.affiliation: *MSc †PhD Grupo de Ciencias de la Visión, Universidad de Murcia, Murcia, Spain (all authors); and Grupo de Investigación en Optometría, Universidad de Valencia, Valencia, Spain (PB-M).
authors.forename: Francisco
authors.initials: F
authors.lastname: Lara
authors.forename: Paula
authors.initials: P
authors.lastname: Bernal-Molina
authors.forename: Vicente
authors.initials: V
authors.lastname: Fernández-Sánchez
authors.forename: Norberto
authors.initials: N
authors.lastname: López-Gil
mesh_terms: D057128:Aberrometry; D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D003315:Cornea / Q000502:physiology; D057108:Corneal Wavefront Aberration / Q000503:physiopathology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D011680:Pupil / Q000502:physiology*; D012029:Refraction, Ocular / Q000502:physiology; D055815:Young Adult