If you understand how the femtosecond laser works in ophthalmic corneal surgery, you know why femtosecond laser surgery is highly safe. Femtosecond laser surgery works on two principles: one is the light transmission principle, and the other is the light blast principle. First, let’s take a look at the light transmission principle of the femtosecond laser: before surgery, the surgeon enters the patient’s basic information data and surgical data into the computer (including the laser focus, the depth of the light blast cutting, the diameter of the corneal flap, the size and width of the tip; the energy of the laser cutting and other data). The surgeon operates the femtosecond laser machine during surgery and flattens the cornea with a flattening cone lens so that the precise distance between the femtosecond laser emitter head and the focus point of each layer of corneal tissue is ensured. The depth of laser focus, which is the distance from the bottom of the flattened cone lens to the laser focus point, allows the femtosecond laser to deliver laser pulses in the pattern set by the surgeon to make various targeted cuts in the cornea. Briefly, the most impressive aspect of the femtosecond laser light delivery principle is the precise directionality and accuracy of the light delivery. Let’s look at the photobursting principle of the femtosecond laser: the laser pulses are focused into the corneal tissue to produce photobursting; for each pulse of photobursting, a micro-ion is produced; for each micro-ion, approximately 1 micron of corneal tissue is evaporated; the evaporated corneal tissue produces extended blisters and CO2 bubbles, which are absorbed by the corneal tissue after which the corneal tissue is thus separated from each other. The computer-controlled optical delivery system generates thousands of laser pulses, thousands of laser pulses in a dense, equal-width, equal-spacing fence-wall grating pattern, focused at the same depth, producing a light burst that forms a layer of tiny diameter bubbles in the corneal tissue, causing the corneal tissue to separate and form the corresponding separation surface, which is the cutting surface of the femtosecond laser. This cutting pattern is used to form the horizontal separation surface and the vertical surface. The laser pulses can also be focused at any angle and in any range of stacking in the corneal tissue to form different angles and ranges of tissue separation. Therefore, the femtosecond laser can be used to slice the cornea to create fine implants and flaps in corneal transplantation and LASIK surgery, or to spot sculpt the cornea to create tunnels in corneal stromal ring implantation surgery.