title: Relative optic cup depth assessments using three stereo photograph viewing methods.
abstract: OBJECTIVE
  A consistent stereoscopic (stereo) effect in disc photographs is important to be certain that apparent depth changes are real and are not the result of artifact caused by a variable stereo angle. The purpose of this study is to compare the accuracy of relative depth assessments using three different stereo photo viewing methods.
  
  
  METHODS
  We evaluated the ability of 12 observers to arrange sets of simultaneous stereo photographs (Nidek 3-Dx split-frame slides, Lentec transparencies) and sequential stereo photographs (Zeiss full-frame slides) according to apparent cup depth. Observer arrangements of each set of 10 photographs were compared to a "reference standard" sequence determined from cup depth measurements made by the Imagenet optic nerve analyzer.
  
  
  RESULTS
  The median number of sequence errors (n = 6) made by all examiners in arranging the Nidek 3-Dx simultaneous stereo slides was significantly lower than the median number of errors (n = 12) with the Zeiss sequential stereo slides.
  
  
  CONCLUSIONS
  Simultaneous stereo slides provide significantly more interobserver consistency for judgements of cup depth than sequential stereo slides.
authors.affiliation: Wills Eye Hospital, William and Anna Goldberg Glaucoma Service and Research Laboratories, Jefferson Medical College, Philadelphia, PA 19107, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Boes
authors.forename: G L
authors.initials: GL
authors.lastname: Spaeth
authors.forename: R P
authors.initials: RP
authors.lastname: Mills
authors.forename: M
authors.initials: M
authors.lastname: Smith
authors.forename: J E
authors.initials: JE
authors.lastname: Nicholl
authors.forename: B C
authors.initials: BC
authors.lastname: Clifton
mesh_terms: D000704:Analysis of Variance; D003867:Depth Perception; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D015588:Observer Variation; D009798:Ocular Hypertension / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results