RELex

RELex is a trade name of Carl Zeiss Meditec from Germany, and uses the femtosecond laser to do what LASIK does.  LASIK currently does this with a combination of a femtosecond laser to create the flap, then an excimer laser to change the corneal shape.  RELex is eliminating the excimer laser step.

It is also called FLEx.  Here the femtosecond laser creates a corneal flap, then removes a lenticule of corneal tissue.  The flap is lifted and the lenticule removed, then the flap repositioned.

A modification of FLEx is SMILE.  This stands for small incision lenticule extraction.  Here only a partial flap is created through a side cut of about 5mm and the lenticule is removed through this side cut.  The possible advantages of the SMILE option include less post-operative irritation due to the smaller corneal epithelial cut, less effect on corneal sensitivity and tear production due to fewer corneal nerves being cut, and the possibility of improving biomechanical stability of the cornea.

The problem with this is that LASIK is a precise procedure when a femtosecond laser is used to produce the flap and then the excimer laser used to remove corneal tissue.  Excimer lasers are precise tools for tissue removal, whereas the femtosecond laser is not.  The femtosecond laser is very good at creating cuts, such as flaps, but is not as precise as the excimer laser in removing and sculpting the new corneal shape.

At this stage SMILE and FLEx, although they have some potential advantages that are yet to be realised, are not as accurate as LASIK using a combination of femtosecond and excimer lasers.  Their main appeal is that they may end up being cheaper because only one laser is required, but at this stage their use is not justified on either safety or accuracy grounds.