What happens in lasik operation?
There are two possible ways to perform refractive operation: first,  to perform the procedure on the cornea, the second - to exchange the crystalline lens with the artificial one. 

The second approach is extremely rare, because the lens (1) is inside the eye and (2) it allows us to accommodate (=change the focus of vision). Thus, this method is relevant only to extremely high myops and people who have some degree of cataract (the clouding of the lens).

In "classic" myopia the eye is larger than "normal" one, and the lens thickness is less relevant in the terms of treatment. 

Back to LASIK - the operation is performed on the cornea: for myopic eye the corneal thickness should be reduced, for hyperopic eye there are other protocols (special thickness reduction).