title: Excimer and Femtosecond Laser Assisted Corneal Transplantation
Creators: name: Seitz, Berthold
name: Flockerzi, Elias
name: Hamon, Loïc
name: Suffo, Shady
name: Daas, Loay
Publisher: name: MyCoRe Community
Year: 2024
Subjects: subject: Corneal Transplantation
subject: Hornhauttransplantation
subject: Femtosecond Laser
subject: Femtosekundenlaser
subject: Excimer
subject: Laser Keratoplasty
subject: 610

description: Purpose: To demonstrate the evolution of laser keratoplasty which started two decades before the clinical introduction of the femtosecond lasers (FSL) and compare the intraoperative feasibility and postoperative outcome of the excimer and femtosecond laser approaches. Methods: Hypothesizing that the properties of the wound bed are of utmost importance for the final optical performance of the graft, Naumann et al. have developed and optimized the technique of non-mechanical corneal trephination using a 193 nm excimer laser along metal masks for penetrating keratoplasty (PKP) since 1986. Starting out with an elliptical trephination the major improvement resulted from the introduction of eight “orientation teeth/notches” at round mask edges minimizing “horizontal torsion”. For non-contact donor trephination from the epithelial side, an artificial anterior chamber was used. Since 1989, more than 6000 PKPs have been performed successfully with the Meditec MEL70® and recently with the Schwind AMARIS 1050S excimer laser in Erlangen and Homburg/Saar. In 2005, we introduced the FSL for “inverse mushroom-shaped” PKP. Since 2006, various groups applied the FSL for PKP with “top hat”, “mushroom”, “zig zag” or “Christmas tree” interface configurations. Results: Prospective clinical studies have shown that the technique of non-contact excimer laser PKP may improve donor and recipient centration, reduce “vertical tilt” and “horizontal torsion” of the graft in the recipient bed, thus resulting in significantly less “all-sutures-out” astigmatism, higher regularity of the topography and better visual acuity. Besides less blood-aqueous barrier breakdown during the early postoperative course after PKP, excimer laser trephination does not induce cataract formation and does not impair the graft endothelium. Likewise, the rate of immunologic graft rejections is not adversely affected by the excimer laser. In addition, trephination of an instable cornea, such as in (pre-) perforated corneal ulcers or after RK or LASIK is facilitated. Clinical results of FSL lamellar or penetrating keratoplasties – requiring variable amounts of applanation thus causing distortion of corneal tissue, especially in keratoconus – are still limited and not yet finally convincing. In a prospective randomized study we and others found that the keratometric astigmatism and incidence of immune reactions after FSL PKP in keratoconus are significantly higher than after excimer laser PKP. After suture removal, mean refractive/topographic (Pentacam and AS-OCT) astigmatism values were significantly lower in the EXCIMER-keratoconus (KC) subgroup (3.0±2.5 D/3.2±2.7 D/3.5±2.9 D) than in the FSL-KC subgroup (7.3±2.8 D/8.1±3.0 D/8.3±3.7 D; p≤0.006). Mean SRI (Surface Regularity Index) was significantly lower in the EXCIMER-KC subgroup than in the FSL-KC subgroup after suture removal (0.57±0.40 vs. 1.16±0.54; p=0.003) indicating a higher regularity of corneal topography in the EXCIMER-KC subgroup. Conclusions: The evolution of non-mechanical laser keratoplasty started in Erlangen in 1986. Because of undisputed clinical advantages, especially in eyes with keratoconus and instable thin corneas after PKP, noncontact excimer laser trephination with orientation teeth/notches is still favored in Homburg/Saar in daily practice. The FSL-assisted keratoplasty technique has been very exciting but due to major lack of all-suture-out data after introduction of the technique 15 years ago – the superiority of this high price and difficult to maintain option has not been proven, yet! FSL-assisted PKP without liquid interface seems to have major disadvantages in comparison to excimer laser PKP especially in keratoconus.
description: Transplantation: Ethics, Techniques, Immunology, p. 67