title: Measurement of ocular alignment with photographic Purkinje I and IV reflection pattern evaluation.
abstract: OBJECTIVE
  To provide reference data for the measurement of ocular alignment and of angles of strabismus with a new stationary photographic apparatus at near and at distance fixation; to verify quantitative relations between the data by comparing experimental data with theoretical predictions.
  
  
  METHODS
  Use of Purkinje I and IV Reflection Pattern Evaluation in conjunction with a new stationary photographic apparatus; application of previously derived equations; simulation of angles of strabismus of 5 degrees and 10 degrees in the primary position.
  
  
  RESULTS
  Data from 62 subjects with orthotropia show good linearity of measured angles in different directions of gaze; a 95% confidence interval for errors up to 18.6% in the simulated angles of strabismus; no need for individual calibration of the apparatus; no bias due to wearing of spherical corrections, and a detection threshold for microstrabismus of +/- 0.35 degrees.
  
  
  CONCLUSIONS
  Data concerning orthotropic and simulated strabismus prove the accuracy of Reflection Pattern Evaluation to assess ocular alignment, for instance, for the diagnosis of strabismus in primary and secondary positions, at near and distance fixation. The measuring range can easily be extended to larger angles of strabismus.
authors.affiliation: Department of Ophthalmology, University Hospital, RWTH Aachen University, Germany.
authors.forename: J C
authors.initials: JC
authors.lastname: Barry
authors.forename: R
authors.initials: R
authors.lastname: Effert
authors.forename: A
authors.initials: A
authors.lastname: Kaupp
authors.forename: A
authors.initials: A
authors.lastname: Burhoff
mesh_terms: D000328:Adult; D000360:Afterimage / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology*; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D009216:Myopia / Q000503:physiopathology; D010781:Photography / Q000295:instrumentation / Q000379:methods*; D011680:Pupil / Q000502:physiology; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D013285:Strabismus / Q000175:diagnosis* / Q000503:physiopathology; D015348:Vision, Binocular