In reply
We thank Dr Harris for his letter to the editor concerning our simplified mathematical model for corneal rotational autograft. We agree with Dr Harris that there are limitations to our simplified model, especially in clinical situations that differ from our stated assumptions. We also agree that moving the scar beyond the pupillary margin and relocating the center of the largest zone of clear cornea over the center of the entrance pupil is the goal of the surgery. To simplify our calculations, we limited our analysis to situations where the center of the pupil and the center of the cornea were in close proximity. In our patient, suturing the intraocular lens would have resulted in a relatively unpredictable shift in the pupil center relative to the corneal center. Another assumption that we made in our simplified model is the circular shape of the cornea. We are currently attempting to generate a more involved mathematical solution assuming a horizontally oval corneal shape and a distance separating the center of the cornea from the center of the pupil. We suspect that in these situations, the displacement may have to be in a direction other than the superior direction; temporal displacement may be more advantageous in some cases (such as the one presented by Dr Harris and as described in the classic article by Bourne and Brubaker).