After CXL , epithelial thickness was significantly thinner 2.5 and 2 mm below and 1.5 mm above the corneal apex ( 49.26 5.69 m ; range : 43 to 62 m ) , and 2.5 and 1 mm nasal and 2 mm temporal to the corneal apex ( 46.66 4.53 m ; range : 39 to 57 m ) compared to preoperative values ( P < .05 for all measurements ) .