Automated detection of ocular focus

David G. Hunter, Kevin J. Nusz, Nainesh K. Gandhi, Imran H. Quraishi, Boris I. Gramatikov, David L. Guyton

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We characterize objectively the state of focus of the human eye, utilizing a bull's eye photodetector to detect the double-pass blur produced from a point source of light. A point fixation source of light illuminates the eye. Fundus-reflected light is focused by the optical system of the eye onto a bull's eye photodetector [consisting of an annulus (A) and a center (C) of approximately equal active area]. To generate focus curves, C/A is measured with a range of trial lenses in the light path. Three human eyes and a model eye are studied. In the model eye, the focus curve showed a sharp peak with a full width at half maximum (FWHM) of ±0.25 D. In human eyes, the ratio C/A was >4 at best focus in all cases, with a FWHM of ±1 D. The optical apparatus detects ocular focus (as opposed to refractive error) in real time. A device that can assess focus rapidly and objectively will make it possible to perform low-cost, mass screening for focusing problems such as may exist in children at risk for amblyopia.

Original languageEnglish (US)
Pages (from-to)1103-1109
Number of pages7
JournalJournal of biomedical optics
Issue number5
StatePublished - Sep 2004


  • Amblyopia
  • Lens opacity
  • Optics
  • Refractive error
  • Screening

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Biomedical Engineering


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