The different forms of laser refractive surgery all have the same aim-to change the corneal curvature, and to thereby change its focusing power and eliminate the need to wear spectacles and contact lenses.
From a patient perspective, it is important to understand the advantages and disadvantages of the different forms of laser refractive surgery, in order to choose the one which is most appropriate for you.
In order that we understand the different procedures, it is important to know something about the cornea.
The human cornea is about 500 microns thick. It has five layers. The top layer, also known as the epithelium is about 50 microns thick. This layer of cells is capable of regeneration. The epithelium can be scraped off the cornea, and it regrows within 3 days.
The second layer is a thin layer known as the Bowman’s membrane. It is the base on which epithelial cells grow. The third layer is known as the stroma. It constitutes the bulk of the cornea, and consists of layer upon layer of clear, ordered cells, which lend the cornea its transparency. The stroma cannot generally regenerate.
The final two layers are the descemet’s membrane and the endothelial cells. These layers are not involved in laser refractive surgery.
Laser Refractive Surgery involves corneal reshaping. Corneal Reshaping is carried out by removing tissue from the corneal stroma. By removing tissue in a precise shape, a new radius of curvature of the cornea can be obtained. Tissue needs to be removed from the Bowman’s layer and stroma, and not the epithelium, because epithelial tissue can regenerate, and negate the effects of our intervention.