Half top hat wound configuration for penetrating keratoplasty: 1-year results

Shaped corneal transplantation surgery

Since its inception in 1905, keratoplasty techniques have continuously evolved. Shaped keratoplasty procedures have allowed corneal surgeons to use complex graft-host junctions and non-circular graft designs to optimise wound strength and healing, facilitate early suture removal and expedite visual rehabilitation. While this was initially limited to penetrating procedures, shaped lamellar keratoplasty techniques have since emerged. Furthermore, the arrival of femtosecond laser has dramatically increased the range of graft designs available to surgeons, due to the technology's ability to precisely cut complex wound edges. This review describes the broad range of shaped keratoplasty grafts currently available and elaborates on their respective advantages and disadvantages in relation to conventional keratoplasty.

[Modern modifications of penetrating keratoplasty with complex operative incision]

The basic principle of modern keratoplasty is selectivity, i.e. the choice of whether to replace only the affected corneal layer. However, when layer-by-layer and interlayer transplantation is not indicated, the method of choice is conventional penetrating keratoplasty. An alternative can be its modifications with complex profiles of the transplant edges and the bed, which are better justified in terms of pathogenesis. The most popular among them are mushroom, zig-zag and top-hat. These surgeries combine optical benefits of penetrating keratoplasty as they do not involve dissection of the corneal optical zone and can negate - to a certain degree - its main downsides such as low trauma tolerance of the postoperative scar, significant level of postoperative astigmatism, and increased visual rehabilitation time. Mushroom-shaped incisions can be performed manually with a femtosecond laser or a microkeratome, zig-zag incision - only with a femtosecond laser. Considering the diversity of keratoplasty modifications with complex operative incisions, further research is required for evaluation of their clinical effectiveness and analysis of postoperative complications.

Corneal transplantation and glaucoma

Glaucoma is the leading cause of irreversible vision loss post-keratoplasty and an important cause of graft failure. With newer techniques, such as lamellar, endothelial, and laser-assisted keratoplasty as well as keratoprosthesis gaining popularity, clinicians will need to consider the incidence, risks, evaluation, and management of glaucoma for each type of keratoplasty when determining which type of transplant may be most appropriate. A comprehensive literature search of glaucoma in the setting of corneal transplantation was performed and serves as the basis for this review. Preexisting glaucoma and aphakia are notable risk factors. Patients that are candidates for deep anterior lamellar keratoplasty may benefit from reduced rates of post-keratoplasty glaucoma. Although glaucoma also complicates eyes with Descemet stripping endothelial keratoplasty, the severity is less and the intraocular pressure is more easily controlled when compared to penetrating keratoplasty. Endothelial keratoplasty creates unique perioperative issues mostly related to management of anterior chamber air bubbles.