The study included 68 shortsighted eyes up to -3.0 diopter sphere , i.e. 198 samples of tears ( per three samples taken from each of the eyes ) , divided into two groups according to the kind of excimer laser intervention performed : the group 1 -- eyes treated by LASIK method ( n = 31 ) , and the group 2 -- eyes treated by the PRK method ( n = 37 ) .