Interferometric testing of soft contact lenses

Gregory A. Williby, Daniel G. Smith, Richard B. Brumfield, John E. Greivenkamp

Research output: Contribution to journalConference article

9 Scopus citations

Abstract

Rapid growth in the contact lens industry towards higher levels of customization has precipitated the need for advances in the metrology techniques and instrumentation used to evaluate soft contact lenses. By measuring the transmitted wavefront, the information needed to evaluate a wide range of lens types (spherical, toric, bifocal) is obtained. A Mach-Zehnder interferometer is used with the lenses tested in saline solution. The lenses must be tested in saline solution to prevent dehydration of the lens, which results in an index change. The lenses are mounted in a cuvette, or water cell, that circulates fresh saline. Calibration of the instrument is complicated by the aspheric wavefronts produced by the lenses and the inherent aberrations picked up by the wavefront as it is imaged from immediately behind the lens to the detector. Simply removing a baseline, no test optic measurement from the measured wavefront does not satisfactorily remove the induced aberrations. Instead, removal of the induced aberrations is achieved by reverse raytracing. In reverse raytracing, the wavefront at the detector is traced back through the system to immediately behind the lens. The use of raytracing code enables theoretical wavefronts to be generated and expected-to-calculated performance evaluations to be made at the transmitted wavefront level.

Original languageEnglish (US)
Pages (from-to)329-339
Number of pages11
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5180
StatePublished - Dec 1 2003
EventOptical Manufacturing and Testing V - San Diego, CA, United States
Duration: Aug 3 2003Aug 5 2003

Keywords

  • Aspherics
  • Interferometery
  • Ophthalmology
  • Optical testing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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