title: Design and validation of an infrared Badal optometer for laser speckle.
abstract: OBJECTIVE
  To validate the design of an infrared wavefront aberrometer with a Badal optometer employing the principle of laser speckle generated by a spinning disk and infrared light. The instrument was designed for subjective meridional refraction in infrared light by human patients.
  
  
  METHODS
  Validation employed a model eye with known refractive error determined with an objective infrared wavefront aberrometer. The model eye was used to produce a speckle pattern on an artificial retina with controlled amounts of ametropia introduced with auxiliary ophthalmic lenses. A human observer performed the psychophysical task of observing the speckle pattern (with the aid of a video camera sensitive to infrared radiation) formed on the artificial retina. Refraction was performed by adjusting the vergence of incident light with the Badal optometer to nullify the motion of laser speckle. Validation of the method was performed for different levels of spherical ametropia and for various configurations of an astigmatic model eye.
  
  
  RESULTS
  Subjective measurements of meridional refractive error over the range -4D to +4D agreed with astigmatic refractive errors predicted by the power of the model eye in the meridian of motion of the spinning disk.
  
  
  CONCLUSIONS
  Use of a Badal optometer to control laser speckle is a valid method for determining subjective refractive error at infrared wavelengths. Such an instrument will be useful for comparing objective measures of refractive error obtained for the human eye with autorefractors and wavefront aberrometers that employ infrared radiation.
authors.affiliation: School of Optometry, Indiana University, Bloomington, Indiana 47408, USA. dfwarren@indiana.edu
authors.forename: Danielle F W
authors.initials: DF
authors.lastname: Teel
authors.forename: R James
authors.initials: RJ
authors.lastname: Copland
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Jacobs
authors.forename: Thad
authors.initials: T
authors.lastname: Wells
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Neal
authors.forename: Larry N
authors.initials: LN
authors.lastname: Thibos
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007259:Infrared Rays; D008962:Models, Theoretical; D009907:Optometry / Q000295:instrumentation*; D012029:Refraction, Ocular / Q000502:physiology; D012030:Refractive Errors / Q000503:physiopathology
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