Influence of femtosecond laser making-flap on surface characteristics of porcine cornea / 中华实验眼科杂志

ABSTRACT

Background The application of femtosecond laser in the corneal refractive surgery has made great progression recent years,but the morphology characteristic of corneal stroma surface after making-flap of femtosecond laser is closely concerned.Objective This study was to analyze the influence of photodisrnption of femtosecond laser on the corneal stroma surface and to investigate the effect of different laser pulse energy on the sudace ultrastructure of corneal stroma.Methods Corneal flaps were made with Visu Max femtosecond laser in 16 fresh porcine eyes with the pulse energy 125 nJ,155 nJ and 195 nJ respectively,and Moria-M2 microkeratome was used as control.Scanning electron microscopy (S-3400N Hitachi High-Technologies Corp) was used to observe and compare the ultrastructural characteristic of corneal stroma bed surface after making of corneal flap.Results The corneal strnma was evaporated and created a smooth surface when photodisrnption happened in the femtosecond laser group.Residual tissue bridges could been exhibited among the cavitation bubbles under the scanning electron microscope.Corneal strnma surface was smooth in the 125 nJ pulse energy group,but some tissue bridges still were visible.In the 155 nJ pulse energy group,much more smooth surface was seen without tissue bridges and mechanical damages on the corneal surface.However,the surface quality was worse and many tissue bridges and grooves existed in the 195 nJ pulse energy group.In addition,different sizes of slots caused by big cavitation bubbles were visible with the round and oval shape.The edges were regular and sharp with small damage zone after cutting with femtoseeond laser.However,many elevated fibril tissues could be seen on the corneal surface after making of flap with microkeratome.Many crimp and irregularity tissues were found on the surface.Blunt surface and indentations appeared in the cutting edge.Conclusions The mierostrueture of corneal stroma surface is more smoother after making of corneal flap with fentosecond laser in comparison with microkeratome.Pulse energy of 155 nJ is preferably during the making-flap with femtosecond laser.