title: A Shack-Hartmann-based autorefractor.
abstract: OBJECTIVE
  Autorefractors are typically based on either the optometer or the Scheiner principles, or a combination of the two techniques. These devices have dominated the market for objective assessment of refractive error for >30 years. The purpose of this investigation is to test a Shack-Hartmann-based system as an alternative to these systems.
  
  
  METHODS
  Fourteen subjects with varying levels of refractive error were measured with a Topcon autorefractor and a Shack-Hartmann-based autorefractor. Fourier transform techniques were used to extract sphere, cylinder, and axis information from the Shack-Hartmann images, avoiding the need for image processing. The deviation of the refractive error from a subjective refraction was used as a means of comparing the two devices.
  
  
  RESULTS
  The two devices performed similarly on this group of subjects. The mean difference in refraction between the two devices was nearly zero, suggesting that the likelihood and magnitude of errors for the two devices are equivalent.
  
  
  CONCLUSIONS
  The Shack-Hartmann-based autorefractor shows promise as an alternative to conventional optometer or Scheiner-based technologies. However, issues with extending the myopic range of the device still need to be resolved.
authors.affiliation: Zygo Corporation, Middlefield, Connecticut, USA.
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Beverage
authors.forename: Jim
authors.initials: J
authors.lastname: Schwiegerling
mesh_terms: D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D006801:Humans; D008433:Mathematics; D012030:Refractive Errors / Q000175:diagnosis*; D015203:Reproducibility of Results