title: Evaluating diffusion of light in the eye by objective means.
abstract: OBJECTIVE
  The authors have developed an index of diffusion that describes the relative spread of light inside and outside the region of image focus of the living human eye. It provides in numerical terms a measure of light scatter and can be used to characterize the optical deficit in eyes with age- and disease-related abnormalities of the anterior segment.
  
  
  METHODS
  An improved version of the double-pass method of examining the aerial image formed by reflection of the retinal image of a point source is employed, together with a new way of analyzing the image. Experimental estimation shows the contaminating effect of back scatter from the media and corneal reflection to be negligible. Measurements are objective and do not require any responses on the part of the patient. Data become available practically on-line.
  
  
  RESULTS
  Index of diffusion values were obtained on 13 patients and varied from 0.22 to 1.04, strongly tending to increase with age. They are rather robust to pupil size, exposure duration, and small amounts of defocus.
  
  
  CONCLUSIONS
  The index appears to provide a promising measure of optical performance of the media of the anterior segment of the eye, which might be useful in studying the effect of aging, injury, and disease.
authors.affiliation: Division of Neurobiology, University of California, Berkeley 94720.
authors.forename: G
authors.initials: G
authors.lastname: Westheimer
authors.forename: J
authors.initials: J
authors.lastname: Liang
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000869:Anterior Eye Segment / Q000503:physiopathology; D004058:Diffusion; D005069:Evaluation Studies as Topic; D005128:Eye Diseases / Q000503:physiopathology; D006801:Humans; D008027:Light; D008875:Middle Aged; D009885:Ophthalmology / Q000379:methods*; D012160:Retina / Q000502:physiology*; D012542:Scattering, Radiation