Top hat wound configuration for penetrating keratoplasty using the femtosecond laser - A laboratory model

Purpose: To evaluate the mechanical stability and induced astigmatism of a modified multiplanar "top hat" wound configuration for full-thickness penetrating keratoplasty (PK) using the femtosecond laser as compared with PK in a laboratory model. Methods: Eight human corneoscleral rims were mounted on an artificial anterior chamber. Four samples were assigned to the traditional PK group. Four samples underwent full-thickness keratoplasty with the femtosecond laser: a 9.0-mm cylindrical cut was made from the anterior chamber into the stroma, followed by a ring-shaped (outer diameter 9.0 mm, inner diameter 7.0 mm) horizontal lamellar resection at two-thirds corneal depth and a 7.0-mm cylindrical cut from the lamellae to the corneal surface. Mechanical stability was evaluated after placement of the cardinal sutures and the running sutures. Results: In the "top hat" PK group, wound leakage occurred at 19 3.36 mm Hg after placement of the cardinal sutures and at 86.25 +/- 9.74 mm Hg after placement of the running sutures. In the traditional PK group, leakage occurred at 0 0 mm Hg and 76.25 +/- 20.98 mm Hg after placement of the cardinal sutures and running sutures, respectively. Both techniques induced steepening of the corneal curvature postop. The modified wound group showed a mean change in average K of 3.43 +/- 3.62 D, whereas the traditional PK group showed a mean change in average K of 3.21 +/- 6.67 D. Conclusion: The femtosecond laser-produced "top hat" wound configuration for PK was found to be more mechanically stable than that produced by the traditional method.