title: The central corneal light reflex ratio from photographs derived from a digital camera in young adults.
abstract: OBJECTIVE
  To determine the normal range of Central Corneal Light Reflex Ratio (CCLRR) from photographs of young adults.
  
  
  METHODS
  A digital camera equipped with a telephoto lens with a flash attachment placed directly above the lens was used to obtain corneal light reflex photographs of 104 subjects, first with the subject fixating on the lens of the camera at a distance of 43 centimeters, and then while looking past the camera to a wall at a distance of 5.4 meters. Digital images were displayed using Adobe Photoshop at a magnification of l200%. The CCLRR was the ratio of the sum of distances between the inner margin of cornea and the central corneal light reflex of each eye to the sum of horizontal corneal diameter of each eye. Measurements were made by three technicians on all subjects, and repeated on a 16% (n=17) subsample.
  
  
  RESULTS
  Mean ratios (standard deviation-SD) from near/distance measurements were 0.468 (0.012)/0.452 (0.019). Limits of the normal range, with 95% certainty, were 0.448 and 0.488 for near measurements and 0.419 and 0.484 for distance measurements. Lower and upper indeterminate zones were 0.440-0.447 and 0.489-0.497 for near measurements and 0.406-0.418 and 0.485-0.497 for distance measurements. More extreme values can be considered as abnormal. The reproducibility and repeatability of the test was good.
  
  
  CONCLUSIONS
  This method is easy to perform and has potential for use in strabismus screening by paramedical personnel.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand. su_ampa@hotmail.com
authors.forename: Suampa
authors.initials: S
authors.lastname: Duangsang
authors.forename: Supaporn
authors.initials: S
authors.lastname: Tengtrisorn
mesh_terms: D000293:Adolescent; D001767:Blinking / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010781:Photography / Q000295:instrumentation; D012016:Reference Values; D055815:Young Adult