The Central Corneal Light Reflex Ratio from Photographs Derived from a Digital Camera in Young Adults
Suampa Duangsang MD*, Supaporn Tengtrisorn MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand
Objective : To determine the normal range of Central Corneal Light Reflex Ratio (CCLRR) from photographs of young adults.
Material and Method: 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 1,200%. 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.
Conclusion : This method is easy to perform and has potential for use in strabismus screening by paramedical personnel.
Keywords : Central corneal light reflex, Photographs, Screening, Strabismus
