title: Assessment of bilateral pupillary centroid characteristics at varying illuminations and post-photopic flash response using an automated pupillometer.
abstract: BACKGROUND
  The aim was to assess the symmetry and magnitude of illumination-dependent centroid shift and of post-photic flash re-dilatation response for normal pupils.
  
  
  METHODS
  This cross-sectional, observational, inter-eye comparative study was performed at a specialty hospital. Fifty eyes (25 volunteers) without any ocular abnormality underwent pupillometry for scotopic (0.4 lux), mesopic (4.0 lux), photopic conditions (40 lux) and for rate of pupillary re-dilatation after a photopic flash (500 lux) with an inbuilt pupillometer on a Scheimpflug device (Sirius, CSO, Italy). Main outcome measures were pupillary centroids at different illuminations and time-dependent pupil diameters after a photic flash response.
  
  
  RESULTS
  The mean pupil size for scotopic, photopic and mesopic pupils were significantly different (p < 0.001, ANOVA) for right and left eyes, analysed separately. The post-photic flash re-dilatation diameter was measured at zero, one, two, four, six, eight and 10 seconds after the flash. The mean diameters at given times post-photic flash were comparable in fellow eyes (p > 0.5, t-test) and highly correlated (r ≥ 0.8, p < 0.05 at all timed comparisons). The mean pupil diameter followed a time-dependent cubic function for both the right and left eyes. Speed was also governed by a time-dependent cubic function for both the right and the left eyes.
  
  
  CONCLUSIONS
  Fellow eye symmetry is seen in illumination-governed centroid shifts and the post-flash re-dilatation response. The pupil dilates back briskly with a time-dependent cubic function, which is similar for fellow eyes in normal patients.
authors.affiliation: Department of Cornea and Refractive Surgery, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates. drgauravprakash@gmail.com.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.affiliation: Department of Cornea and Refractive Surgery, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates.
authors.forename: Dhruv
authors.initials: D
authors.lastname: Srivastava
authors.affiliation: Department of Cornea and Refractive Surgery, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Suhail
authors.affiliation: Department of Cornea and Refractive Surgery, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates.
authors.forename: Ruthchel
authors.initials: R
authors.lastname: Bacero
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*
keywords: automated pupillometry; centroids; redilatation