Your eye is gently held open by an instrument, so it’s virtually impossible for you to close your eye during the procedure. During the actual tissue removal with the laser (ablation) the Allegretto Wavelight system uses a sophisticated tracking system that measures the position of your eye hundreds of times per second. The laser follows your eye and is therefore always perfectly centered on target. If for some reason your eyes suddenly moves to a degree that the laser loses it lock, it will not fire a pulse. One major advantage of the latest Allegretto laser is it fires 500 times a second! So treatments that take minutes with older lasers take seconds with the EX500.