SBK is also a type of LASIK, called anterior subelastic laser keratomileusis, which is thinner than what is generally referred to as ultra-thin LASIK, with a flap thickness of about 100 microns, almost like making a flap under the anterior elastic layer of the cornea, which is the limit of the thickness of the LASIK flap, and cannot be made thinner. Thinner becomes EK or TPRK type of surface surgery, which takes about a month to recover and is more painful. In addition, the keratome used for SBK is the one use plus keratome, which produces a smoother and more controllable flap than the usual rotary keratome. In short, SBK means that the thickness of the flap is so thin that it is almost like making the flap under the anterior elastic layer. So the SBK of the corneal flap made with a mechanical knife in general is also called OUP-SBK; and the corneal flap made with a femtosecond laser can also be very thin, around 100 microns, so there is also a femtosecond laser SBK. In short, the thinner the corneal flap made for LASIK surgery, the better, and SBK is better than ultra-thin. And your cornea 570 microns, relatively thick, 400 degrees is not too high, with ultra-thin is also more than enough, but always SBK is less damage to the cornea. Corneal surface surgery: TPRK>EK>PRK, generally choose TransPRK (TPRK: trans-epithelial laser keratomileusis), this is a unique surgical procedure of Amaz Excimer. The surgery is very precise, more advanced than the general, is all-laser.