The distortion of pupil size in anterior segment photographs due to corneal refraction and observation direction

Abstract

Measurement of the pupil size is important in various researches. Commercially available pupillometer can measure monocular pupil size, however, bilateral simultaneous measurement is required for neuro-ophthalmologic examination. For this purpose, anterior segment photographs are frequently used. Because the cornea acts as the convex lens, pupil size will be magnified on the photograph, and the magnification will be determined by the refractive power of the cornea which varies person to person. For a more accurate measurement, compensation of the refraction effect is needed. An eye model is proposed that covers up the effect of the corneal refraction. This model can also give solution when the eye is deviated from neutral position. © 2011 Springer-Verlag Berlin Heidelberg.