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

 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.

 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.

 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.

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

 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.

Raster Low Single Raster Low Multiple Raster High Single Spiral Low Multiple

 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.

 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.

 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.

References: Sarayaba MA et al. Femtosecond Laser Posterior Lamellar Keratoplasty. Cornea. 2005;24: Suwan-apichon O et al. Mickrokeratome Versus Femtosecond Laser Predissection of Corneal Grafts for Anterior and Posterior Lamellar Keratoplasty. Cornea. 2006;25: Binder PS et al. Characterization of Submicrojule femtosecond laser corneal tissue dissection. J Cataract Refractive Surgery. 2008;34: 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: 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.