With the increasing maturity and popularity of excimer laser in situ keratomileusis (LASIK), the LASIK procedure has gradually evolved from the conventional thick flap to a thin flap, of which SBK is the most popular thin flap LASIK procedure in the ophthalmic community in recent years. It is an intermediate procedure between superficial and lamellar surgery, in which an ultra-thin flap of approximately 90-ll0 microns in thickness is created using a disposable microkeratome or femtosecond laser and laser cutting is performed under the anterior elastic layer of the cornea, leaving the anterior elastic layer intact. Compared to superficial surgery, the anterior elastic layer is preserved for better biomechanics, and the flap is so thin that deeper fibrous tissue is not lost; more of the corneal stromal bed is preserved than in traditional LASIK surgery, preventing postoperative corneal dilatation and the occurrence of medically induced cone corneas; because the tip of the flap is left on the nasal side, the nasal trigeminal nerve endings are preserved, significantly reducing the occurrence of early postoperative dry eye. SBK is favored by more and more ophthalmologists and myopic patients for its unique advantages, such as fast recovery of vision, good visual quality and higher safety.