In order to perform refractive surgery, fs-laser pulses were focused into animal cornea. During histo-pathological analysis by light- and transmission-electron-microscopy new side effects of fs-photodisruption were found. Due to the high intensities at the focal region, self focusing followed by further nonlinear effects is observed, leading to streak formation inside the cornea and several micro-breakdowns on the sub-micron scale. The nature and origin of these streaks are further investigated.