Keratocyte survival following a controlled-rate freeze.

One of the major drawbacks of cryorefractive surgery is the delay in the postoperative recovery of corneal clarity. The authors have hypothesized that this delay is due to the death of graft keratocytes caused by the freezing process, and the need for subsequent repopulation by host keratocytes to restore corneal clarity. By using a slow, controlled-rate freeze on a modified Barraquer cryolathe, the authors are able to maintain keratocyte viability in the graft corneal tissue, as assessed by standard histologic methods and by collagenase digestion. Maintenance of keratocyte viability results in the rapid return of corneal clarity following lamellar keratoplasty in the rabbit, with few of the histopathologic changes seen following standard rapid freezing of corneal tissue.