What is SMILE xtra or LASIK xtra ? It is an extra or additional or extra procedure called cross linking added to strengthen the cornea at the time of corneal laser procedure. This is done to increase the biomechanical strength of the cornea as laser weakens corneas. This is done in few cases where the surgeon feels that it’s risky to do laser alone. Instead of the conventional one hour cross linking procedure done for keratoconus, an xtra procedure uses a higher strength riboflavin for 90 second