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Femtosecond Assisted Descemet Stripping Automated Endothelial Keratoplasty ( DSAEK ) Donor Tissue Preparation. Natalie Stanciu, MD Richard M. Awdeh, MD Takeshi Ide, MD Sonia Yoo, MD Bascom Palmer Eye Institute ASCRS 2009: San Francisco. Background.
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Femtosecond Assisted Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) Donor Tissue Preparation Natalie Stanciu, MD Richard M. Awdeh, MD Takeshi Ide, MD Sonia Yoo, MD Bascom Palmer Eye Institute ASCRS 2009: San Francisco
Background • 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.
Background • 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.
Hypothesis • 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.
Methods • 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 Multiple Raster Low Single Spiral Low Multiple Raster High Single
Results • 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.
Limitations • 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.
Conclusions • 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.
Thank You 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.