title: Factors influencing the pupillary light reflex in healthy individuals.
abstract: OBJECTIVE
  To determine the ocular anatomical factors influencing the pupillary light reactions to different wavelengths of light, measured with chromatic pupillometry.
  
  
  METHODS
  Community-based, cross-sectional study including subjects with normal ocular health (ages 50-79 years). Direct pupillary responses to continuously increasing irradiances (6.8 to 13.8 log photons cm(-2) s(-1)) of red (631 nm) and blue (469 nm) light were measured, using a dedicated infrared pupillometer. All subjects underwent swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) and noncontact partial coherence laser interferometry (Lenstar LS900, Haag-Streit AG, Switzerland). Univariate and multivariable regression analyses were performed to determine the anatomical features influencing pupillographic parameters.
  
  
  RESULTS
  Among the 177 included subjects, 167 (94.4 %) were Chinese and 116 (65.5 %) female. The average baseline pupil diameter in darkness (β = -0.080, p < 0.001) and the amplitude of the relative pupillary constriction (β = -0.233, p = 0.006) to blue light decreased with age. The amplitude of pupillary constriction was significantly larger in patients with a thinner iris, in response to stimulation with blue (β = -0.321, p < 0.001) and red light (β = -0.336, p < 0.001). Other ocular parameters (i.e., lens vault, anterior chamber depth width, iris volume, iris curvature, and lens thickness) were not significantly associated with pupillometric outcomes.
  
  
  CONCLUSIONS
  The amplitude of the pupillary light constriction to chromatic photic stimuli is reduced with increasing age and iris thickness in subjects with normal ocular health, a finding which needs to be integrated into future pupillometric studies.
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.
authors.forename: Sourabh
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.
authors.forename: Mani
authors.initials: M
authors.lastname: Baskaran
authors.affiliation: Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Annadata V
authors.initials: AV
authors.lastname: Rukmini
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.
authors.forename: Monisha E
authors.initials: ME
authors.lastname: Nongpiur
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Eye ACP, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: HlaMyint
authors.initials: H
authors.lastname: Htoon
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.|Eye ACP, Duke-NUS Medical School, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Cheng
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.
authors.forename: Shamira A
authors.initials: SA
authors.lastname: Perera
authors.affiliation: Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore.|Department of Physiology, Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Gooley
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore.|Singapore National Eye Center, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, Singapore, Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.affiliation: Singapore Eye Research Institute, 11, Third Hospital Avenue #5-00, SNEC Building, Singapore, 168751, Singapore. dan.milea@snec.com.sg.|Singapore National Eye Center, Singapore, Singapore. dan.milea@snec.com.sg.|Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore. dan.milea@snec.com.sg.
authors.forename: Dan
authors.initials: D
authors.lastname: Milea
mesh_terms: D000368:Aged; D000867:Anterior Chamber / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology*; D012016:Reference Values; D012025:Reflex, Pupillary / Q000502:physiology*; D041623:Tomography, Optical Coherence; D014794:Visual Fields
keywords: Intrinsically photosensitive retinal ganglion cells; Iris thickness; Pupil; Pupillary light reflex; Pupillometry