1. Effect of an irregular anterior surface on a lamellar femtosecond laser cut Robert E. Fintelmann, MD Michele M. Bloomer, MD Bennie H. Jeng, MD Authors have no financial interest Department of Ophthalmology University of California San Francisco Jengb@vision.ucsf.edu

2.  First femtosecond laser approved in 2000 to create lamellar cuts for LASIK  Now being used for  Anterior and posterior lamellar keratoplasty  Customized trephination for penetrating keratoplasty  Tunnel creation for intracorneal ring segments  Astigmatic keratotomy Introduction

3. Purpose  To determine if the femtosecond laser be used to create reliable cuts under an irregular corneal surface.

4. Methods  Three types of defects created  Rectangle at 210µm  Manual 2.5 mm punch  Manual triangular defect  Three corneas masked with hydroxypropylmethylcellulose  Three corneas without masking agent

5.  Lamellar cuts created with femtosecond laser (300µm depth, 9mm Diameter, power 3mJ, IntraLase, Model FS60, software v 1.12 Abbott Medical optics, Abbott Park, IL)  Corneas examined with ocular coherence tomography (RTVue SD-OCT with CAM-L lens) (Figure 1)  All corneas were then fixed in formaldehyde, cut through the created defect and examined under the microscope

6. Figure 1: OCT of Defects En face OCT of rectangle Transverse OCT of rectangle

7. Results  Femtosecond laser creates a smooth cut under irregular surfaces (Figure 2)  Irregularities on the surface can lead to differences in thickness in the bed (Figure 3)  No difference in bed appearance between masked and unmasked corneas

8. Figure 2: OCT of bed Thinning of bed under defect Bed under punch Bed under rectangle

9. Figure 3: Histopathology of cornea under defect Thicker bed outside area of defect Thinner bed in area under defect

10. Discussion  Femtosecond lasers can help changing an irregular surface into a smooth bed for a corneal transplant  Small study size insufficient to quantify the variability in the beds  Masking agent does not appear to be necessary for producing regular beds

11.  A corneal graft with a regular surface placed into the now smoother bed may give a good clinical outcome

12. References  Ratkay-Traub I, Juhasz T, Horvath C, et al. Ultra-short pulse (femtosecond) laser surgery: initial use in LASIK flap creation. Ophthalmol Clin North Am. 2001; 14(2): 347-355, viii-ix.  Harissi-Dagher M and Azar DT. Femtosecond laser astigmatic keratotomy for postkeratoplasty astigmatism. Can J Ophthalmol. 2008; 43(3): 367-369.  Ignacio TS, Nguyen TB, Chuck RS, Kurtz RM and Sarayba MA. Top hat wound configuration for penetrating keratoplasty using the femtosecond laser: a laboratory model. Cornea. 2006; 25(3): 336-340.  Malta JB, Soong HK, Shtein R, et al. Femtosecond laser-assisted keratoplasty: laboratory studies in eye bank eyes. Curr Eye Res. 2009; 34(1): 18-25.  Rabinowitz YS, Li X, Ignacio TS and Maguen E. INTACS inserts using the femtosecond laser compared to the mechanical spreader in the treatment of keratoconus. J Refract Surg. 2006; 22(8): 764-771.  Seitz B, Langenbucher A, Hofmann-Rummelt C, Schlotzer-Schrehardt U and Naumann GO. Nonmechanical posterior lamellar keratoplasty using the femtosecond laser (femto-plak) for corneal endothelial decompensation. Am J Ophthalmol. 2003; 136(4): 769-772.  Yoo SH, Kymionis GD, Koreishi A, et al. Femtosecond laser-assisted sutureless anterior lamellar keratoplasty. Ophthalmology. 2008; 115(8): 1303-1307, 1307 e1301.