Centering corneal surgical procedures.

Currently used methods for centering corneal surgical procedures emphasize the visual axis of the eye but do not define it properly. We obtained the best optical result by centering the surgical procedure on the line of sight and entrance pupil of the eye, not on the visual axis. We found an error of 0.5 to 0.8 mm in currently used methods of marking the visual axis, which arose from the use of the corneal light reflex as a sighting point or from inadvertent monocular sighting in techniques requiring binocular sighting. Proper centering requires the patient to fixate on a point that is coaxial with the surgeon's sighting eye, and the cornea is marked at the point in line with the center of the patient's entrance pupil, ignoring the corneal light reflex.