Epikeratophakia: the surgical correction of aphakia. I. Lathing of corneal tissue.

Epikeratophakia is a newly developed form of refractive corneal surgery for the correction of hyperopia. In this procedure, a piece of donor corneal tissue is lathed to a specific dioptric power. The epithelial cells are removed from the recipient cornea, and the donor tissue is sutured to the front of the eye. The resulting change in corneal curvature provides the visual correction, as, for instance, in the correction of aphakia. We describe here the computational analysis used to lathe human donor corneal tissue for use as epikeratophakia grafts. With these equations, the precision of the observed thickness of the lathed lenticule was +/- 0.05 mm and the precision of the observed diameter was +/- 0.25 mm. We found that, in a graft of a given diameter, the smaller the optical zone, the greater the maximal dioptric power of the graft, limited only by the central thickness of the donor cornea and the mechanical limitations of the cryolathe. In our case, the highest theoretical correction obtainable was 37 diopters.