1. Natalie Stanciu, MD Richard M. Awdeh, MD Takeshi Ide, MD Sonia Yoo, MD Bascom Palmer Eye Institute ASCRS 2009: San Francisco

2.  45,000 PKP are performed annually in the US, 45% include cases of corneal damage limited to endothelium.  DSAEK: popular alternative to PKP.  Most DSAEK tissue is cut with microkeratome  Limitations of microkeratome: inability to control the thickness and shape of donor tissue.  One potential reason why BCVA after DSAEK rarely 20/20.

3.  Recently the use of Femtosecond laser has been entertained as an alternative to mechanical mickrokeratome.  Advantage: Ability to control thickness and predictable shape.  Challenge is achieving smooth surface: a problem less encountered by microkeratome.

5.  Variables which can affect smoothness Low vs. High Energy Single vs. Multiple Pass Laser pattern: Raster vs. Spiral  In this pilot study, we compared relative smoothness of femtosecond-cut tissue using several different combinations of above variables.  We predict that Raster, Low, Multiple pass should produce the smoothest surface.

6. GroupEnergySpot Separation (microns) Line Raster Low Single 1.066 Raster Low Multiple 1.066 Raster High Single 1.9119 Spiral Low Multiple 1.066

7.  Fresh porcine eyes(n=2 for each group)  30 kHz INTRALASE Femtosecond laser was used to cut cornea flap.  Following the procedure, the donor tissue was immersed in fixative.  Scanning Electron microscopy(SEM) was used to assess relative smoothness of tissue.

8. Raster Low Single Raster Low Multiple Raster High Single Spiral Low Multiple

9.  Raster Low Single pass appeared to have smoothest surface.  Contradicts expected results however possible error introduced when multiple pass done in different directions.  Observed that easier to lift flap with multiple pass than single.  Overall raster smoother than spiral.

10.  Delay between fixating tissue and sending for SEM (environmental).  Challenge interpreting SEM picture without bias.  Sample size low.  Femtosecond 30kH machine used here may make extrapolating results to other laser machine difficult.

11.  Ideal to use human eyes in the future, using pig eyes may have introduced some error and difficulty in applying results.  Possible use of software programs to quantify analysis of SEM photos.  Principles applied here can hopefully bring us closer to achieving perfect visual outcome following DSAEK.

12. References: Sarayaba MA et al. Femtosecond Laser Posterior Lamellar Keratoplasty. Cornea. 2005;24:328-333. Suwan-apichon O et al. Mickrokeratome Versus Femtosecond Laser Predissection of Corneal Grafts for Anterior and Posterior Lamellar Keratoplasty. Cornea. 2006;25:966-968. Binder PS et al. Characterization of Submicrojule femtosecond laser corneal tissue dissection. J Cataract Refractive Surgery. 2008;34:146-152. Terry MA, Ously PJ. Replacing the endothelium without corneal surface incisions or sutures:the first United States clinical series using the deep lamellar endothelial keratoplasty procedure. Ophthalmology. 2003;110:755-764. Terry MA, Ously PJ. Endothelial replacement without surface corneal incisions or sutures: topography of the deep lamellar endothelial keratoplasty procedure. Aiken-Oneil P, Mannis MJ. Summary of corneal transplant activity Eye Bank association of America. Cornea. 2002;21:1-3.