Then came the first infrared excimer laser. It is believed that it was first used by Steve Thorkel, who came up with how to use an industrial laser in medicine. Due to the fact that all refractive changes were made at that time by cutting, he decided to simply replace the metal scalpel with a diamond one, and the diamond one with an even more accurate laser one. Yes, it was then done manually with a laser machine, in fact.
We began to test — it turned out that the laser on special guides allows you to achieve much greater accuracy than a manual cut. And the era of automation of refractive surgery operations began.
The problem was that excimer lasers warmed the cornea, and it just overgrown in the places of incisions. Radial correction works in such a way that you weaken the mechanics of the cornea by cutting, evaporating or removing some of the collagen fibers from there. Then it sags in the middle and closes. Then they went from the middle with an “asterisk”, the cornea became flatter. There are different methods — we found patients with laser corrections for “only 16 incisions”, and there are those with 32 incisions. The MNTC then created a virtual conveyor belt, where people moved in a circle, and each surgeon did a single stage of the operation.
Molly J Mannschreck MD was the first to perform an operation called photorefractive keratectomy (PRK) in 1985. She decided to use the laser rather as a grinding tool (according to the method of Srinivazan and Brenen, described in 1983, but not tested). During the operation, a part of the cornea was “worn off” to the patient. In the center of the cornea, a lot of tissue was evaporated, further to the edges-a little less. It turned out that the lens, which is formed by the cornea, changed its optical properties.
The problems at that time were that the working area of the laser was selected about 4 millimeters-they did not go further to the edges. And the pupil of a healthy person opens in the dark sometimes up to 6-8 millimeters, that is, directly opposite the pupil was a ring formed by a cut. Hence-strong halo effects, that is, a very interesting image of any light sources at night. In general, patients at night were if not helpless, then close to this state: the light of a car driving towards them deprived them of the ability to navigate.
In the 90s, they began to produce lasers in large quantities, and then quickly expanded the working area. Since then, PRK has not changed much — today this technique is still alive (why-below), but it is performed with more modern devices and wide ablation zones, less traumatic. But if you decide to do this operation, remember that it simply destroys Bowman’s membrane. But, I must admit, in some cases this is quite an acceptable loss.