Superficial and deep methods of laser vision correction, that is, what does the phrase “laser vision correction” really mean?
Laser vision correction (defect) (laser refractive surgery) is a very precise and empowering way of interfering with the eyeball and modeling the anterior surface of the cornea with a laser, leading to the removal of the vision defect.
The history of laser refractive surgery dates back to the ’80s. PRK (or photorefractive keratectomy) has been a surgical procedure performed since the late ’80s and is considered one of the older methods of refractive laser surgery. The first successful procedure using an excimer laser, on the other hand, was performed by Dr. Theo Seiler in 1987. The invention of the LASIK method is credited to Joannis Pallikaris. In 1995, the U.S. Food and Drugs Administration (FDA) approved the excimer laser and approved PRK, or photorefractive keratectomy, as a generally available medical procedure.
Professional laser treatments are preceded by precise qualifying examinations to determine, among other things. Whether the visual defect has stabilized and there are no contraindications to the procedure.
Short-sighted, hyperopic and astigmatic people, as well as those suffering from so-called presbyopia (presbyopia), are eligible for the surgery, or rather procedures – because laser vision correction is performed with various methods that are constantly being developed and improved. The latest surgical technologies make it possible to combine myopia/farsightedness/dystopia surgery with simultaneous removal of other vision defects, such as astigmatism.
Laser correction of (defective) vision is now not only the best alternative to traditional glasses and contact lenses, but also the safest way of surgical intervention in the eyeball.
During laser eye surgery, the patient does not undergo general anesthesia. Laser vision correction is performed under local anesthesia (anesthetic drops are instilled into the eyes) in an outpatient setting.
The rapid development of ophthalmic techniques makes laser eye surgery a maximum-safety procedure. The number of complications is less than 1% of cases. For any medical procedure, the term “guarantee” is not used, but “effectiveness of the procedure.” The laser vision correction procedure is effective in approx. 95%. Statistics on laser vision correction report that about 95 percent of those operated on achieve a quality of vision safe for driving after the procedure.
Laser vision correction procedures take 15-20 minutes, and within a few hours to a few weeks (depending on the technique used) patients regain perfect vision.
Surface methods: EBK, PRK, TransPRK
The procedures involve removing the upper cell layer of the cornea (epithelium) and then properly reshaping the underlying corneal tissue using an excimer laser. In superficial methods, the removed epithelium undergoes natural recovery after the procedure. Surface methods are characterized by a slightly longer healing time and a smaller extent of defect removal than in deep methods.
The difference between the various superficial treatments lies in the way the epithelium is removed:
- PRK – the epithelium is completely removed, after being softened with an alcohol solution. After mechanical removal, the epithelium grows back naturally, which involves a longer time for the eye to heal and return to normal vision.
- EBKTM (Epithelial Bowman’s Keratectomy) is a modification of the LASEK and PRK methods. The epithelium is precisely removed with an Epi-Clear knife, which gently and in a fully controlled manner prepares the cornea for the procedure, leaving its deeper layers intact. Compared to other surface methods, after EBKTM the epithelium regenerates up to twice as fast, and the regeneration process is smoother than in other surface methods.The EBK method is the first choice method for a relatively small group of patients. At the same time, this procedure is distinguished by its lower price due to the cost of the equipment used and materials after the procedure.
- TransPRK – is done exclusively with an excimer laser and involves corneal profiling and removal of the corneal flap without the use of surgical instruments. Trans-PRK stands for Trans-epithelial PhotoRefractive Keratectomy. Corneal epithelial and dioptric correction is done simultaneously uniquely with the excimer laser. This is the most modern method of vision correction that can be performed under surface methods.
Deep methods
In deep methods, a corneal flap is produced, which fuses over time.
LASIK
In the method LASIK with a microkeratome (scalpel), the incision on the cornea is made with a microprecision knife. The ultra-thin flap (130 microns to 180 microns) is carefully deflected, and then the inside of the cornea is exposed to the excimer laser and reshaped so that the focus point is optimally on the retina. Then the flap is resealed, and the cornea heals within a few days.
FemtoLASIK (All-Laser-LASIK).
Method FEMTO-LASIK, also known as All-Laser-LASIK, is the next step in the development of the modern LASIK method. In traditional LASIK laser treatment, the cornea is cut with a scalpel (microkeratome), which carries certain risks. In the modern FEMTO-LASIK method, the cornea is opened with a high-precision femtosecond laser.
The operation of the laser is computer-controlled, the surgeon also has a microscope at his disposal, which guarantees maximum precision and selection of the diameter thickness of the separated corneal flap. The flap is raised on a “hinge” so that it can undergo corneal modeling with an excimer laser. For more information, see the post titled. “Don’t listen to what people say – listen to your doctor (1) FemtoLASIK or ReLEx® SMILE?”.
SBK-LASIK
In the traditional method, the deflectable corneal flap is 130 microns to 180 microns thick – in the SBK-LASIK method, only 90-100 microns. This is the advantage of the action of the special Carriazo-Pendular microkeratome head. Thanks to such precise manipulation on the cornea, the SBK-LASIK method can benefit people who have not previously qualified for laser vision correction due to a cornea that is too thin, too much myopia, or a combination of both.
EPI-LASIK
In this variation of the method, the surgeon uses an epikeratome – a tool that allows laser correction on the corneal surface itself, without intervening in the deeper layers.
Unlike traditional LASIK, the epithelial flap is not cut off here, thus minimizing traumatization of the corneal stroma. EPI-LASIK is therefore recommended for people whose lifestyle may involve an increased risk of experiencing eye trauma – athletes, soldiers, policemen, etc. This method is safe for patients with corneas that are too thin, which disqualifies them for other laser methods.
ReLEx® SMILE Method
Method ReLEx® SMILE Belongs to the so-called “free” methods. Inside the intact cornea, a so called “free” is created. lenticula (a thin section of the lens in the cornea). A minimally invasive incision is then made for the approach. The intraocular lens can then be removed through this small opening.
In this method – called the “keyhole” method – the corneal flap (flap) is not formed or cut. The procedure is performed through a small incision on the cornea, and is therefore minimally invasive.
This means that there is also minimal interference with the cornea, so the healing process of the eye is very short. The procedure is performed with the VisuMax® femtosecond laser, delineating the tissue to be removed for better vision.
During the procedure, a so-called microlens (lenticule) is debulked in the corneal dermis, which is removed through a small incision. First, the VisuMax® femtosecond laser works deeper – the posterior refractive surface of the microlens is formed, which is responsible for the main power change.
Next, the anterior surface of the lenticule is prepared slightly higher up. After incising the edges, the surgeon efficiently removes the microlens from the corneal parenchyma. The incision that breaches the corneal epithelium is much smaller than in methods that require debulking the flap.
