Intrastromal refractive surgery by ultrashort laser pulses: side effects and mechanisms

摘要

The Feasibility of refractive surgery with ultrashort laser pulses in the fs-regime was stuided. The experiments were performed with an Erbium fibrelaser oscillator, which was amplified by means of chirped pulse amplification in a Titanium-Sapphire regenerative amplifier. With this system pluse durations of 180 fs and pulse energies of up to some hundred um J were possible. The photodisruption was performed in corneal tissue in order to create corneal incisions and lamellars. Surface quality and htermal damages of the cuts inside the tissue were studied with the help of micromorphological analysis, such as scanning electron microscopy (SEM) kand histological sections. high level precision along with minimal thermal damage could be observed. Saline solution as a model substance was used for studying side effects as bubble formation and pressure trransients. The pressure measurements were performed using composition of different gas constituents with the help of flash photography and gas chromatography. The results demonstrate the minimal invasive treatment of corneal stroma by fs-photodisruption. Studies of secondary effects indicate, that additional processes have to be considered.