Numerical modeling of imaging of the eye pupil through the cornea

In the experimental pupilometry one measures and analyses the size of the pupil image, which is observed through the optical system of the cornea. The size of the real pupil is different from this image. We have applied the out of axis ray tracing method using MATLAB environment (ca. 7000 rays) to calculate the properties of the pupil image. Calculations have shown that the observed image of the pupil is greater than the real pupil and is located in front of it. This concerns the size of the pupil image and its position as a function of the central corneal curvature, eccentricity of the elliptic approximation of the corneal profile and the size of the real pupil. Results show that differences in magnification of the virtual image of the pupil can reach 15%. Moreover the image of the pupil is always blurred. The quality of the image depends on the diameter and position of the optical system for observation of the pupil, the geometry of the cornea and the size and position of the real pupil. In the case of the nonrotational cornea, the image of the plain and circular real pupil is not plain and not circular anymore, what additionally limits the sharpness of the observed pupil image.