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The concept of top hat wound configuration for penetrating keratoplasty (TH-PKP) was introduced to ophthalmology 50 years ago by Jose Barraquer, who named it "a keratoplasty in two planes." 1 Busin from Italy reported in 2003 his experience with this novel wound configuration. 2 This technique combined the visual outcomes of PKP with the wound-healing advantage of lamellar keratoplasty. This manual top hat dissection technique has not reached worldwide popularity due to the time required in preparing this top hat shape donor and recipient, with actually similar visual outcomes to conventional PKP. Recently, we analysed our outcomes with the manual TH-PKP in comparison with the conventional PKP, and found that TH-PKP speeds up suture removal and contributes to higher endothelial cell counts in the grafts 1 year after surgery. 3
An easier and more precise way to create the top hat wound configuration is to use of the femtosecond laser, which has been used in the last decade for flap creation in lamellar refractive surgeries. During the last 3 years, several groups 4 - 6 have determined the feasibility of using the femtosecond laser in a human cadaver eye model to create the "top hat" wound configuration for PKP. The mechanical stability and induced astigmatism of this novel procedure were compared with the traditional PKP procedure and were found to be more mechanically stable than those produced by the traditional method, 4 - 6 and even more stable than other wound configurations created by the femtosecond laser itself. 7 Several publications have appeared since 2007, reporting on the preliminary results of femtosecond laser top hat and zigzag wound configuration for PKP. 8 - 12 Those reports demonstrated biomechanically stable wound, excellent wound apposition and faster recovery of best-spectacle corrected visual acuity visual acuity (BSCVA) with moderate astigmatism.
The main aim of this study was to compare, for the first time, the visual outcomes and complication rate of femtosecond laser (IntraLase Corp. Irvine, California) enabled top hat PKP (IEK) versus retrospective data on non-laser, manual top hat PKP (TH-PKP) and conventional PKP cases.
PATIENTS AND METHODS
In this prospective non-randomised study, we included 94 patients who underwent corneal transplantation at the cornea service of the Toronto Western Hospital, Toronto, Canada. Of these 94 patients, 23...