As we can see from the history and trends of keratoconus development, with the development of technology and equipment, the effect and safety of refractive surgery have been sufficiently guaranteed, and people’s attention has begun to focus on postoperative corneal biomechanical changes. Corneal biomechanics is simply understood as the ability of the cornea to resist dilation, i.e., the ability of corneal tissue to resist pressure within the eye. The integrity of the corneal layers and structure is a key factor in maintaining normal corneal biomechanics, and since refractive surgery is based on the correction of refractive error by cutting a portion of the corneal stroma, postoperative corneal biomechanics may be affected to a greater or lesser extent. Current refractive surgery is subject to a rigorous preoperative examination to ensure that postoperative biomechanical changes are kept within safe limits. Of course, depending on the patient’s eye, multiple surgical procedures may be able to meet this requirement, but there are some differences in the impact on corneal biomechanics after different refractive procedures. In normal human corneal tissue, the anterior elastic layer (Bowman’s membrane) and the corneal stroma are generally considered to play a critical role in maintaining corneal biomechanics. The anterior corneal stromal lamellae are more densely arranged than the posterior, with more tilted branching and cross-linking, and the stroma of the peripheral cornea is also more ductile than the central zone, so that corneal tension resistance gradually decreases from the anterior to the deeper stroma, and from the peripheral to the central cornea. The rate of loss of corneal antitension in corneal flaps of different thicknesses When analyzing different keratoconus procedures, they can be broadly divided into surface surgery and interlaminar surgery. Surface surgery includes PRK, LASEK, epi-LASIK, and the latest transepithelial PRK surgery; interlayer surgery includes various LASIK surgeries, and it is still controversial whether SBK is also classified as surface surgery or interlayer surgery, but the author believes that it should be classified as interlayer surgery in terms of surgical principles. The stromal part cut by surface surgery is the most superficial stroma, and the range is the size of the treated optical area, and the retained stromal part is more peripheral stromal and relatively more anterior stromal; interlayer surgery produces a corneal flap containing a certain amount of anterior stromal, and then starts laser treatment from under the flap, because the healing method between the stromal is scar healing, so the tension resistance of the corneal flap and stromal bed will be greatly reduced after healing, so after interlayer surgery The stromal portion lost after interlaminar surgery is equivalent to the size and thickness of the anterior-most stroma of the corneal flap and the anterior-middle stroma of the optical area, while the retained stromal portion is relatively less in the peripheral and anterior stroma, so the biomechanical changes after interlaminar surgery are greater than those after surface surgery. Therefore, the biomechanical changes after SBK are between surface surgery and conventional LASIK. Comparison of Corneal Stromal Tension Resistance at Different Sites The latest LASIK procedure without a flap is theoretically less biomechanical than preoperative because the peripheral stroma is almost completely preserved and the central anterior stroma is equally intact, allowing internal pressure transfer to the periphery. Of course, there is still a lot of controversy regarding biomechanics, and some studies have shown that removal of the anterior elastic layer does not change the corneal biomechanical properties. The posterior elastic lamina (Descemet’s membrane) is malleable and low stiffness, and can effectively buffer a certain range of IOP against corneal morphology.