Surface Quality of Femtosecond Dissected Posterior Human Corneal Stroma Investigated With Atomic Force Microscopy

Purpose: To investigate and compare the surface roughness and morphology of posterior stromal lenticules created with a femtosecond laser using various pulse energies to that obtained with a mechanical microkeratome. Methods: A 150 kHz femtosecond laser platform (IntraLase iFS; Abbott Medical Optics) was programmed to create an 8.5-mm-diameter posterior stromal lenticule in 12 human corneal tissues. Specimens were dissected using different pulse energies (1.00, 0.75, 0.65, and 0.50) and fixed 2 mu m spot separations. Three additional posterior corneal lenticules were prepared using a mechanical microkeratome (Moria Evolution 3; Moria). After the procedure, each corneal tissue was examined by atomic force microscopy (Autoprobe CP; Veeco). Results: Femtosecond laser-treated tissues revealed similar morphological features, however, with significant differences in surface roughness in relation to the energy pulse used for lamellar dissection (P < 0.001). The most regular stromal surface was achieved when using 0.50 mu J pulse energy; on the contrary, the roughest specimens were those dissected using 1.00 mu J pulse energy. No differences in surface roughness were measured between mechanically resected tissues and those treated using 0.50 mu J pulse energy (P > 0.05). Conclusions: Atomic force microscopy submicron analysis of femtosecond-dissected donor tissues provided quantitative demonstration of the relation between pulse energy and stromal surface roughness. Surface quality of posterior corneal lenticules, comparable with that provided by mechanical microkeratome, is significantly improved when setting pulse energy for lamellar dissection of 0.50-mu J and 2-mu m spot separations.