title: Photoreceptor orientation in iris coloboma.
abstract: OBJECTIVE
  Investigate photoreceptor orientation and alignment in an observer with a simple coloboma of the iris and no retinal involvement.
  
  
  METHODS
  Using a psychophysical procedure, extensive measurements of the Stiles-Crawford functions of the first kind (SCE I) were obtained from this observer.
  
  
  RESULTS
  In this observer, the usual center-of-the-exit-pupil-of-the-eye alignment tendency of photoreceptors (inferred from the peaks of the SCE I functions) is absent. The inferred orientation of photoreceptors at numerous retinal loci tested lies outside the pupil, opposite the direction of the downwardly displaced pupil center.
  
  
  CONCLUSIONS
  These results add support to previous suggestions that nonphototropic forces such as retinal tractional forces should be considered as an integral part of the mechanism(s) subserving human photoreceptor alignment in both normal and anomalous observers.
authors.affiliation: Southern California College of Optometry, Fullerton.
authors.forename: J E
authors.initials: JE
authors.lastname: Bailey
authors.forename: V
authors.initials: V
authors.lastname: Lakshminarayanan
authors.forename: J M
authors.initials: JM
authors.lastname: Enoch
mesh_terms: D003103:Coloboma / Q000503:physiopathology*; D006801:Humans; D007498:Iris / Q000002:abnormalities*; D008027:Light; D008297:Male; D008875:Middle Aged; D010786:Photoreceptor Cells / Q000503:physiopathology*; D011601:Psychophysics; D011680:Pupil / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology