title: Influence of stop position on spectacle magnification.
abstract: OBJECTIVE
  To develop and use equations of spectacle magnification when the limiting stop is either the entrance pupil of the eye or an artificial pupil in front of a lens.
  
  
  METHODS
  Spectacle magnification was determined for ophthalmic lenses in air and for water environments. The reference was the retinal image for an uncorrected eye in air with a natural pupil.
  
  
  RESULTS
  When an artificial pupil is placed in front of lenses, spectacle magnification is hardly affected by lens power, unlike the usual situation where the natural pupil is used. The water environment provides interesting influences in which spectacle magnification is highly sensitive to the distance between the cornea and eye entrance pupil. In water, retinal images are approximately 18% bigger than in air. Wearing air-filled goggles in water increases retinal image size by about 13% compared with that when they are not worn.
  
  
  CONCLUSIONS
  The equations extend earlier understanding of spectacle magnification and should be useful for those wishing to determine magnification of ophthalmic lens systems when artificial pupils and environments such as water are used.
authors.affiliation: *PhD, DSc, FAAO †PhD, DSc School of Optometry and Vision Science and Institute of Health and Biomedical Innovation, Queensland University of Technology, Queensland, Australia (DAA); and Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom (WNC).
authors.forename: David A
authors.initials: DA
authors.lastname: Atchison
authors.forename: W Neil
authors.initials: WN
authors.lastname: Charman
mesh_terms: D005139:Eyeglasses; D006801:Humans; D008433:Mathematics; D055095:Optics and Photonics; D011680:Pupil / Q000502:physiology