| | Precision Surgery | There are other refractive surgeries called Radial Keratotomy (RK) and Photorefractive Keratectomy (PRK) which is used for reshaping the cornea.
PRK is the first surgical procedure aim of which was to change the shape of cornea by means of sculpting with a help of laser. Genuenly it is an outpatient procedure largely performed with local anesthetic eye drops. The way of work which is typical for such type of refractive surgery is to fondly reshape the cornea. Therefore microscopic amounts of tissue are putting away from the outer surface with a cool ultraviolet ray of light managed by computer. Due to it’s precision the beam can cut scores in a string of human hair without any damage or breaking, interestingly that every other pulse is able to retain 39 millionth of an inch of tissue in 12 billionths of a second.
RK, in its turn, deals with a very keen knife which is cutting slices in the cornea and as a result modifies its initial shape. The procedure is accounted for a short period of time, as a rule not more than a couple of minutes and patients are entirely return to their routine work in one to three days. The other surgical procedure - LASIK was evolved afterwards.
The main difference between these two types of surgeries is that the stroma, (the middle layer of the cornea), is unprotected before it is vaporized with the laser. For instance, in PRK epithelium - the top layer of the cornea, it is scraped away to show the stromal layer underneath. To compare, in LASIK, a flap is cut in the stromal layer and the flap is folded back.
Thermokeratoplasty – is the following type of refractive surgery, here in order to change the shape of cornea the heat is applied. The cause of the heat can be a laser also, as for that which is used for LASIK and PRK, but some differences exist. Other refractive devices contain corneal ring segments that are interjected into the stroma and special contact lenses that provisionally change the shape of the cornea (orthokeratology).
|
|
