Top-hat shaped corneal trephination for penetrating keratoplasty using the femtosecond laser: a histomorphological study.

PURPOSE: To evaluate a novel technique for penetrating keratoplasty (PK) with the use of a new software algorithm for the femtosecond laser, designed to create penetrating cuts in a top hat configuration.

DESIGN: Consecutive histomorphological case series.

PATIENTS AND METHODS: Twelve eyes of 12 patients underwent penetrating keratoplasty by means of a 60-kHz femtosecond laser (IntraLase, Irvine, California) with a software specifically developed for corneal surgery. Of the 12 patients, the reason for keratoplasty was keratoconus in 4 patients, bullous keratopathy in 6 patients, keratotorus in 1 patient, and status post chemical burn in 1 patient. A new software was used to create penetrating cuts in a top-hat-shaped configuration. In all cases, cutting parameters were identical in all donor and corresponding host corneas: 7.0 mm diameter of the anterior side cut, 8.5-8.7 mm diameter of the posterior side cut, and a depth of 300 microm for the lamellar cut. In all cases, a complete penetrating cut with the laser in the host cornea was not intended intraoperatively. Complete penetration was performed subsequently and manually with a diamond knife because of logistic conditions. Trephined corneoscleral rings and button corneas were analyzed macroscopically and histologically to determine cut quality.

RESULTS: All procedures were performed without any complications. With application of appropriate combinations of pulse energy and spacing, trephination took less than 200 seconds. Macroscopic examination and histology of donor and recipient specimens showed a straight, smooth cut with perpendicular edges in all donor buttons. No corneal edema and no visible damage to the keratocyte nuclei were found. At the region of manual dissection, a small stromal tissue-tag was present in parts of the circumference in all donor buttons. No evidence of any cut complication was noted.

CONCLUSIONS: Top-hat-shaped penetrating keratoplasty using the IntraLase femtosecond laser enables a quick and sufficient trephination of both human donor and host corneas. It creates favorable histomorphological results with regard to cut quality of the donor and host corneas.