Effective corneal refractive zone in terms of Gaussian optics

The portion of the cornea that transmits light for vision is clinically important in several contexts, including corneal ablation in refractive surgery. In contrast to geometric optics, Gaussian optics allows one to obtain simple, explicit formulas for the geometry of the effective corneal refractive zone for distant object points that are on or off the line of sight. In this article, Gaussian optics was used to derive the formula for the diameter of the zone and, when the zone is annular, the inner and outer diameter, as a function of corneal power, anterior chamber depth, pupil diameter, and angular position of the object point.