[Perspectives of femtosecond laser-assisted keratoplasty]. / Perspektiven der Femtosekundenlaser-assistierten Keratoplastik.

The femtosecond laser technique allows completely new trephination procedures in penetrating and lamellar keratoplasty. With femtosecond laser-assisted penetrating keratoplasty it is possible to perform profiled trephination, such as top hat and mushroom profiles. Thus, it is easier to get a watertight wound closure intraoperatively and due to the larger wound surface wound healing is faster and allows early complete suture removal. In lamellar keratoplasty the femtosecond laser enables the surgeon to cut to any depth in the corneas resulting in thin corneal donor buttons, e.g. for DSAEK. In this manuscript an overview is given of the state of the art and of the perspectives of femtosecond laser keratoplasty.

Corneal lathing using the excimer laser and a computer-controlled positioning system.

PURPOSE: To present the excimer laser corneal shaping system (ELCS-S), an add-on device to the Keratom, a commercially available 193-nm excimer laser built by Schwind. METHODS: The system is designed for the preparation of donor corneas under sterile conditions using the ultraviolet laser to offer greatest possible flexibility. Lenticules for planolamellar grafting and refractive epikeratoplasty, as well as donor buttons for penetrating keratoplasty can be computer-designed by the surgeon or technician and lathed with the system. RESULTS: Using the excimer laser corneal shaping system (ELCS-S) on human donor corneas, the central surface of the epikeratoplasty lenticule exhibited only narrow, flat concentric notches corresponding to the single lathing steps. Transmission electron microscopy revealed a damage zone of less than 0.3 microm in close approximation to the treated surface. The final thickness revealed a difference of less than +/-53 microm from the intended, initially programmed value. Ultrastructural studies showed the perpendicular stromal surface of the penetrating keratoplasty buttons to be smooth with minimal protrusion of Descemet's membrane. Endothelial injury was observed in a zone averaging between 40 and 100 microm adjacent to the cutting edge only. CONCLUSION: The excimer laser corneal shaping system (ELCS-S) allows a computer-controlled, surgeon-designed, sterile preparation of lamellar and penetrating corneal grafts with the use of the excimer laser. This could offer significant advantages in comparison to presently available systems for lamellar dissection and trephination.

[Live epikeratophakia and deep lamellar keratoplasty for I-III stage-specific surgical treatment of keratoconus]. / Lebend-Epikeratophakie und Tiefe Lamelläre Keratoplastik zur Stadiengerechten chirurgischen Behandlung des Keratokonus (KK) I-III.

BACKGROUND: Perforating keratoplasty (PKP) for the treatment of keratoconus is a temporary procedure that sacrifices the healthy recipient endothelium. As an alternative to PKP we perform live-epikeratophakia (L-EPI) in keratoconus I-II and deep lamellar keratoplasty (DLKP) in keratoconus II-III. PATIENTS AND METHODS: 20 patients with keratoconus were operated on either with L-EPI for keratoconus I-II (n = 10) or DLKP for keratoconus II-III (n = 10) respectively. In all cases, corneal tissue eligible for corneal transplantation was used. L-EPI: The corneal lenticule was prepared by means of the Barraquer-Krumeich-Swinger (BKS) set. The recipient cornea was trephined to a depth of 0.3 mm with the Guided-Trephine-System (GTS). The incision was extended manually (inner diameter 7.0 mm, outer diameter 9.0 mm). No keratectomy was performed. The lenticule was fixed with a 10 x 0 nylon double-running anti-torque suture (DRA). DLKP: The recipient cornea was trephined with the 8.0 mm GTS to a depth of 0.68 mm. A lamellar removal of the upper layers was performed by hand. After mechanical removal of the graft endothelium, the remaining full thickness donor cornea was sutured into the bed with a 10 x 0 nylon DRA suture. RESULTS: L-EPI: Within this series, there was no disturbance of the healing process. Spherical equivalent and corneal astigmatism remained stable from the first month on. Visual acuity of 20/40 or better was obtained in 40% of the cases at 1 month, 53% at 6 months, and 100% at 1 year and 2 years. We did not observe any late decline of VA. Two patients with kerato-conus borderline stage II did not reach useful VA due to insufficiently reduced pre-existing irregular corneal astigmatism. These patients successfully underwent DLKP at 8 and 10 months respectively. DLKP: Except for 1 case (neurodermatitis), all lenticules remained stable with respect to refraction and radii up to the longest follow-up of 2 years. Starting from the first month on, refraction was stable. Visual acuity of 20/40 or better was reached in 33% of the cases at 1 month, in 56% at 6 months, and in 89% at 1 and 2 years. We did not administer systemic cyclosporine-A in either group. In the lamellar techniques presented, we did not observe any graft rejection. According to corneal topography, corneal astigmatism, spherical equivalent, and keratometry we did not observe any late re-onset of a progression of the cone. CONCLUSION: In patients with keratoconus stage I to III, L-EPI or DLKP appeared to be very useful therapies. Both procedures seem to end progression of the disease and allow to preserve the healthy recipient endothelium. If unsuccessful, either procedure may be repeated. Neither procedure precludes possibly later needed PKP.

[Method of designing a mold for processing corneal lenticules in epikeratophakia with excimer laser].

PURPOSE: To design a mold for processing optical power in epikeratophakia. METHOD: With excimer laser a corneal graft with appropriate optical power shall be got on the formula of the mold's radius curvature. RESULTS: Based upon the formula from the data, a 12D mold was accomplished to obtain a suitable cornea lens for epikeratophakia. CONCLUSION: The 12D mold presents the value to some extent in processing the desired optical power of corneal graft for those patients requiring epikeratophakia.

Trephination with vacuum trephine in undercorrection of myopic epikeratoplasty.

For the treatment of undercorrection after myopic epikeratoplasty, early suture removal, scar revision, retrephination, replacement of lenticule and, recently, excimer laser photorefractive keratoplasty have been employed. We performed trephination with Hessburg-Barron vacuum trephine on 11 eyes of 11 patients whose post-epikeratoplasty myopic power was over -4.00 diopters for 3 consecutive months. Patients were followed up on post-trephination 1 month, 3 months and 6 months. The mean duration from epikeratoplasty to trephination was 14.27 months, the mean pre-trephination spherical equivalent was -8.50 D and the mean keratometric reading was 40.87 D. The mean reduction of spherical equivalent was -4.07, -5.99, -8.02 D at post-trephination 1, 3, 6 months, respectively. The mean keratometric reading was 37.60 diopters at 1 month and 41.53 diopters at 6 months. At 1 and 3 months, there were significant reductions of myopic power in refraction and keratometry (p < 0.01), but, at 6 months, regression to pre-trephination levels took place (p > 0.05). There was no change of uncorrected and best corrected visual acuity between baseline and post-trephination 6 months.

Trephination with vacuum trephine in undercorrection of myopic epikeratoplasty

For the treatment of undercorrection after myopic epikeratoplasty, early suture removal, scar revision, retrephination, replacement of lenticule and, recently, excimer laser photorefractive keratoplasty have been employed. We performed trephination with Hessburg-Barron vacuum trephine on 11 eyes of 11 patients whose post-epikeratoplasty myopic power was over -4.00 diopters for 3 consecutive months. Patients were followed up on post-trephination 1 month, 3 months and 6 months. The mean duration from epikeratoplasty to trephination was 14.27 months, the mean pre-trephination spherical equivalent was -8.50 D and the mean keratometric reading was 40.87 D. The mean reduction of spherical equivalent was -4.07, -5.99, -8.02 D at post-trephination 1, 3, 6 months, respectively. The mean keratometric reading was 37.60 diopters at 1 month and 41.53 diopters at 6 months. At 1 and 3 months, there were significant reductions of myopic power in refraction and keratometry (p 0.05). There was no change of uncorrected and best corrected visual acuity between baseline and post-trephination 6 months.