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Research Papers

In situ monitoring of second-harmonic generation in human corneas to compensate for femtosecond laser pulse attenuation in keratoplasty

[+] Author Affiliations
Valeria Nuzzo, Karsten Plamann

Laboratoire d'Optique Appliquée, ENSTA-Ècole Polytechnique-CNRS UMR 7639, Chemin de la Hunière, 91761 Palaiseau Cedex, France and Laboratoire Biotechnologie et Œil,Université René Descartes, Paris V, EA 4063 Hôpital Hôtel Dieu, 1 place du parvis Notre Dame, 75181 Paris Cedex 4, France

Michèle Savoldelli

Université René Descartes, Laboratoire Biotechnologie et Œil, Paris V, EA 4063 France and Hôpital Hôtel Dieu, 1 place du parvis Notre Dame, 75181 Paris Cedex 4, France

Michele Merano

Ecole Nationale Supérieure de Techniques Avancées, CNRS UMR 7639, Laboratoire d’Optique Appliquée, Chemin de la Hunière, 91761 Palaiseau Cedex, France

David Donate

Université René Descartes, Laboratoire Biotechnologie et Œil, Paris V, EA 4063 France and Hôpital Hôtel Dieu, 1 place du parvis Notre Dame, 75181 Paris Cedex 4, France

Olivier Albert, Pedro Felipe Gardeazábal Rodríguez

Ecole Nationale Supérieure de Techniques Avancées, CNRS UMR 7639, Laboratoire d’Optique Appliquée, Chemin de la Hunière, 91761 Palaiseau Cedex, France and Université René Descartes, Laboratoire Biotechnologie et Œil, Paris V, EA 4063 France and Hôpital Hôtel Dieu, 1 place du parvis Notre Dame, 75181 Paris Cedex 4, France

Gerard Mourou

Ecole Nationale Supérieure de Techniques Avancées, CNRS UMR 7639, Laboratoire d’Optique Appliquée, Chemin de la Hunière, 91761 Palaiseau Cedex, France

Jean-Marc Legeais

Université René Descartes, Laboratoire Biotechnologie et Œil, Paris V, EA 4063 France and Hôpital Hôtel Dieu, 1 place du parvis Notre Dame, 75181 Paris Cedex 4, France

J. Biomed. Opt. 12(6), 064032 (November 16, 2007). doi:10.1117/1.2811951
History: Received October 25, 2006; Revised August 21, 2007; Accepted August 21, 2007; Published November 16, 2007
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The application of femtosecond lasers in corneal transplant surgery requires high pulse energies to compensate for the strong optical scattering in pathological corneas. However, excessive energies deteriorate the quality of the incisions. The aim of this study is to demonstrate the dependence of side effects on local radiant exposure, numerical aperture, and tissue properties, to quantify the penetration depth of the laser for individual corneas, and to provide a method for optimizing the energy in the volume of the cornea. We examine histological and ultrastructural sections of clear and edematous corneas with perforating and lamellar incisions performed at different pulse energies. We demonstrate that the augmented energies in edematous corneas may result in unwanted side effects even when using high numerical apertures. The dependence of the laser beam penetration depth on pulse energy is evaluated by histology and an exponential decrease is observed. We show that the penetration length can be determined by evaluating the backscattered second-harmonic emission associated with the nonlinear optical properties of the tissue. This approach represents a noninvasive method for the in situ quantification of the laser beam attenuation, enabling us to adapt the pulse energy accordingly. Experiments using adapted energies show that the side effects are minimized.

© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Valeria Nuzzo ; Karsten Plamann ; Michèle Savoldelli ; Michele Merano ; David Donate, et al.
"In situ monitoring of second-harmonic generation in human corneas to compensate for femtosecond laser pulse attenuation in keratoplasty", J. Biomed. Opt. 12(6), 064032 (November 16, 2007). ; http://dx.doi.org/10.1117/1.2811951


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