© 2011 Wichtig Editore - ISSN 1120-6721 Eur J Ophthalmol ( 2011; : 00) 000-000 00 1 INTRODUCTION Commercial femtosecond laser platforms make use of near-infrared pulsed laser to generate photodisruption, a photo-chemo-mechanical process that allows corneal tis- sue to be cut with micrometric precision. In recent years, advancements in technology have resulted in considerable improvements in the accuracy of corneal Femtosecond laser photodisruptive effects on the posterior human corneal stroma investigated with atomic force microscopy Sebastiano Serrao 1 , Marco Lombardo 1 , Maria P. De Santo 2,3 , Giuseppe Lombardo 2,4 , Domenico Schiano Lomoriello 1 , Pietro Ducoli 1 , Mario Stirpe 1 1 IRCCS Fondazione G.B. Bietti, Rome - Italy 2 CNR-IPCF Unit of Cosenza, c/o LiCryL Laboratory, Rende (CS) - Italy 3 Department of Physics, University of Calabria, Rende (CS) - Italy 4 Vision Engineering, Rome - Italy PURPOSE. To analyze the effects of femtosecond laser pulses on the posterior human corneal stroma with atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM). METHODS. A femtosecond laser (IntraLase iFS, Abbott, USA) was programmed to create a full posterior lamellar dissection in 9 human corneal tissues, using 3 different pulse energies (1.00 µJ, 0.75 µJ, and 0.50 µJ). Three corneal tissues were prepared in a similar fashion using a mechanical microkeratome (Moria Evolution 3, Moria, France). Six corneal tissues received an 8.00-mm diameter full cylindrical resection using either the femtosecond laser or the Barron trephine (Katena Products Inc., USA). The posterior corneal lenticules were first examined at AFM (Autoprobe CP, Veeco, USA). Both the pos- terior lenticules and the trephined corneal samples were scanned by ESEM (FEI Quanta 400, USA). RESULTS. Granules and crater-like features were observed on the stromal interface of all the laser dis- sected tissues, likely due to a secondary thermal effect of femtosecond laser dissection. Collagen fibers were seen only on samples treated with the 0.50 µJ pulse energy. Images of an even stromal surface were observed on the posterior stroma of mechanically dissected corneal samples. CONCLUSIONS. Mechanical and thermal effects, induced by femtosecond laser pulses on the human corneal stroma, were seen with AFM. Surface regularity of the photodisrupted stroma was inversely and non-linearly related to the pulse energy. The femtosecond laser provided high surface quality for lamellar resection of the posterior stroma comparable to those provided by mechanical devices. KEY WORDS. Atomic force microscopy, Femtosecond laser, Human corneal tissue, Scanning electron microscopy Accepted: December 14, 2011 ORIGINAL ARTICLE surgery using femtosecond lasers: the systems are able to dissect the tissue up to the desired depth and to sculpt borders with angled profiles. Researchers have demon- strated the versatility of the femtosecond lasers in corneal surgery, including corneal transplantation, post-kerato- plasty astigmatic keratotomy, and laser in situ keratomileu- sis (LASIK) (1-5). Only a few studies have investigated the effects of ultrashort laser pulses with human corneal tis- DOI: 10.5301/ejo.5000113