**1. Introduction**

76 Keratoplasties – Surgical Techniques and Complications

Morrison, J.C., & Swan, K.C. (1982). Full-thickness lamellar keratoplasty. A histopathologic

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Sugita, J., & Kondo, J. (1997). Deep lamellar keratoplasty with complete removal of pathological stroma for vision improvement. *Br J Ophthalmol* , 81, 184-188. Thomas, C.L., & Purnell, E.W. (1965). Prevention and management of early and late

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580.

The concept of lamellar keratoplasty (LK) is that of targeted lamellar replacement of corneal tissue while retaining normal cornea. It involves replacing anterior stroma at different deepness with an anterior lamellar keratoplasty (ALK). Despite the significant advantages of LK surgery, penetrating keratoplasty (PK) remains the most common procedure, largely because lamellar surgery is more technically demanding and time consuming 1. Moreover, interface irregularity arising from manual lamellar dissection often results in suboptimal visual outcomes 2. Long-term graft survival rates and endothelial cell counts after PK continue to drop for many years after surgery, clearly showing the disadvantage of unnecessary replacement of a healthy endothelium in anterior-stromal disorders 3. For these reasons, PK is now being replaced by various types of lamellar techniques that aim to replace damaged tissue only, while maintaining healthy tissue intact.

Recent improvements of surgical techniques and advances in instrumentation, such as microkeratome-assisted LK (ALTK) 4, and excimer laser assisted LK (ELLK), 5,6 have contributed to improve visual quality in corneal lamellar surgery, promoting a paradigm shift in the surgical treatment of anterior corneal disease.

The new femtosecond laser technology has been introduced for ophthalmic surgery in the last years with the aim to resolve the microkeratomes related problems in LASIK surgery 7. This new technology has been shown to be the "top" to perform LASIK flaps, creating flaps of precise and homogeneous thickness, reducing the flap related problems (free cap, button hole, flap irregularity) and leaving more stroma for the excimer ablation allowing to correct higher refractive defects (especially with the ultrathin flaps of 90 microns).

Moreover, the femtolaser technology, allowing to perform precise corneal cuts with a planned and customized shape, offers clear advantages also applied in anterior lamellar keratoplasty (ALK) surgery8-10.

Penetrating Keratoplasty (PK) is still the most common and effective technique for corneal transplantation, but is an "open sky" surgical technique and could be complicated by choroidal effusion or haemorrage, spontaneous lens expression and vitreous loss 1. Moreover, this technique is characterized by an everlasting endothelial cell loss, leading to corneal decompensation necessitating a re-PK to restore a clear graft. To avoid these risks, more conservative surgical techniques have been proposed for the treatment of anterior corneal pathologies with healthy endothelium, enclosed in the great chapter of the lamellar keratoplasty (LK) 2, 3. So that, during the last 10 years, to increase the results of traditional

Femtosecond Laser Assisted Lamellar Keratoplasties 79

corneal pathologies (5 post-traumatic corneal scar, 3 post-keratitis corneal leucoma, and 13

The femtosecond laser of the Ophthalmic Department of Catholic University of "Sacro Cuore" (Figure 1) features are as follows: spot size of < 3µm, repetition rate of 60 kHz (for the first 10 patients the repetition rate was 15kHz); laser pulse duration of 600-800 fs (±50); maximum laser pulse peak power of 12 MW (±2); central laser wavelength of 1053nm; maximum pulse energy of 7.3 mJ (±0.7); maximum laser beam output of 110mW (±11). The laser acts with four different ablation patterns (Raster, double raster, spiral and pocket) that can be mixed by the surgeon for the surgical target. The femtosecond laser pulses result in multiple corneal intrastromal gas bubbles (micro-cavitations), requiring only a manual light lamellar dissection

The first step was performed in the laser room where a femtosecond laser cut was created on both donor and receiving cornea(Figure 2). In the second step, performed in the surgery room, the donor lamella was sutured into the receiving stromal bed with 16 radial 10/0

To realize the donor lamella, the cut was performed on an entire donor cornea, analyzed and delivered by an ocular tissue bank, positioned on an artificial anterior chamber (Moria, France). Mean lamellar diameter was 8.34mm ± 0.28 SD (range: 8.2 - 8.7mm), and mean lamellar thickness was 353.91µm ± 38.82SD (range: 220 - 400µm). The donor button has been planned thicker than the amount of receiving cornea removed, in way to restore a normal corneal thickness (at least 550 micron), and 0.2 mm larger, in way to avoid too much corneal compression with the sutures and to evade the risk of anterior chamber (AC) reduction after

Fig. 2. Femtosecond laser cut on recipient bed after docking on the cornea of the patient.

using a blunted spatula, to create the intrastromal cut with a smooth surface.

The Femto-ALK surgical technique has been realized in two surgical steps:

moderate keratoconus).

**2.3 Surgical procedure** 

nylon stitches.

surgery.

**2.2 Femtosecond laser features** 

manual ALK, the use of high technologic tools such as microkeratomes or excimer lasers with customized ablation patterns has been proposed, with uncertain outcomes 4-6.

With the aim to realize a more safe, repeatable and effective LK technique, suitable to every surgical skills, in 2005 we started to use the femtosecond laser technology (IntraLase, AMO, USA) (Figure 1,2) in several cases of anterior corneal pathologies (Femtolaser-assisted Anterior Lamellar Keratoplasty – Femto-ALK -. Early data published on Cornea in 2008) 9. With the diffusion of the new manual techniques of DALK, especially the "Big Bubble" one11-15, allowing the better visual results ever reached by a ALK, the Femto-ALK technique resulted quite inadequate. For these reasons, we developed a more effective femtolaser assisted lamellar technique: the Femtolaser-assisted Deep Anterior Lamellar Keratoplasty (Femto-DALK). Below the description of our Femtolaser-assisted LK techniques and the results reached after more than two years of follow-up with these two techniques.

Fig. 1. The femtosecond laser (IntraLase, AMO, USA) settled near the excimer laser (Technolas 217C, Bausch & Lomb, USA) in the Laser Room of the Ophthalmic Department of Catholic University of " Sacro Cuore" of Rome, Italy.
