Laser in situ keratomileusis
"In situ" = in place, in the normal place; "Kerato" = Cornea; "Mileusis" = shape, model
Lasik is a surgical procedure with which visual defects in the eyes can be corrected using a laser. Both short (Myopia) and farsightedness (Hyperopia) and astuteness (astigmatism) can be operated on with the help of Lasik. The term Lasik means something like "the cornea (" kerato ") on the spot (" in situ ") using a laser (" laser ") to shape (" mileusis ")".
Read more on the topic: Laser eye
Lasik has been used as an eye laser procedure since 1990.
Lasik is part of the so-called refractive Corneal surgery. This includes surgery on the cornea of the eye with the aim of that Eyesight (Visus) to improve. The cornea forms the front boundary of the human eye and, together with the eye lens, is responsible for the refraction of light and thus for the Visual acuity responsible, with the cornea about two-thirds and the lens makes up about a third of the refractive power. Thus, interventions on the cornea that change its refractive power (for example Lasik) can influence visual acuity.
Before a Lasik can be done, a number of measures must be taken to prepare for surgery. On the one hand it belongs to everyone surgical intervention a detailed discussion with the patient about the Lasik, which should address the process of the Lasik, the risks and complications, alternative treatments and postoperative care.
On the other hand, specific eye examinations must be carried out in advance for an eye operation. These include an ultrasound-controlled Dimension of the corneal thickness (Pachymetry), one Analysis of the corneal bulge (topography), one Measurement of the length of the eyeball (Eyeball length) and an examination of the tear film (composition, production, etc.). Also the Pupil size (Pupillometry) and the Intraocular pressure must be determined before performing a Lasik. It is also important to have a "contact lens-free" phase before the operation: Patients should not wear soft lenses for the last two weeks before the Lasik operation.
Advantages and disadvantages of Lasik
The great advantage of Lasik lies in the extensive freedom from pain immediately after the operation. In addition, the desired vision is achieved very quickly (within a few days) and there is only a very low risk of scarring of the cornea, which in turn would cause discomfort and impaired vision.
Depending on the type of procedure - it is an invasive surgical procedure - arise Disadvantages of Lasik. Incision errors and infections can occur due to the invasiveness. In addition, after a Lasik there is a risk of epithelial ingrowth, especially on the cut edges of the corneal flap.
In general, a further disadvantage of Lasik results from the limited applicability of this method. Not all visual defects can be remedied, but there are limits with regard to the strength of the visual defect, since the cornea can only be removed up to a certain residual thickness. This should not be less than 250 µm. For myopia (Myopia) this means a limit of eight diopters for Lasik Farsightedness (Hyperopia) of four Diopters and for Astuteness (astigmatism) of six diopters.
Contraindications that do not allow Lasik surgery to be performed include various points. On the one hand, this is not done if the patient's demands on the result cannot be met with the help of Lasik.
On the other hand, changing, unstable visual defects are still forming, Age under 18 years such as Infections of the eye (for example bacterial or viral diseases) a contraindication for a Lasik. Not only pathogen-related, but also autoimmune-induced inflammation prohibit the use of a Lasik. These autoimmune diseases include those of the connective tissue, so-called collagenoses, as these cause ulcers to form eye (Ulcers) favor. Wound healing disorders and new blood vessels (Neovascularization) at the Choroid (Choroid) are also contraindications for Lasik, as the latter increase the risk of bleeding during the operation.
Furthermore, in the case of untreated lesions, the Retina (retina) Lasik are not performed, as these can be aggravated by the procedure (especially by the suction process) and the risk of Blindness given is. Visual defects that are too severe (see “Disadvantages”) are also contraindications, since in this case too much cornea would have to be removed for optimal correction, so that the excessively thin remnant that remains can change pathologically. For example, corneal ectasia can develop, which is characterized by a protrusion of the cornea.
Likewise, in the case of changes in the deeper layers of the cornea or in the case of reduced wetting of the cornea with the body's own Tear fluid no Lasik should be performed. The last are pregnancy as well as a lack of cooperation from the patient (Incompliance). For example, this person must be ready to consistently fix a point during the Lasik (eye tracking).
To interpret a successful result, the following information is given on results of the Lasik that differ either by half a diopter or a whole diopter from the desired value.
When correcting foresightedness (Myopia) Lasik has a success rate of approx. 84% with a deviation of 0.5 Doptria from the desired visual acuity. If the range is extended to a deviation of one doptrie, a successful result is even available in 95% of the cases treated as part of the Lasik. When treating Farsightedness lower success rates are achieved. A maximum deviation from the desired result is reached at approx. 70%, the success rate with a visual acuity deviating by one diopter is 91%.
The result of the Lasik depends on the conditions of the operation as well as the instruments used and the individual requirements of the patient. The re-laser rate after a Lasik is 10-20%.
Alternative procedures to Lasik
There are other refractive methods surgerywhich are used to treat the cornea. These include the photorrefractive Keratectomy (PRK), the Laser epithelial keratomileusis (Lasek) as well as the epithelial laser in situ keratomileusus (Epi-Lasik). All of these procedures also use a laser to modify the cornea and make use of the principle of so-called surface ablation, including an ablation (ablation) of the corneal surface is to be understood.
The keratectomy used in photorefractive keratectomy means something like "Cutting out the cornea". The surface of the cornea is ablated with the laser, but without cutting the flap that is typical for Lasik.
With the Lasek, the uppermost corneal layer, the epithelium, is peeled off with the help of alcohol, then the underlying tissue is lasered and finally the peeled-off epithelium is placed back on the defect.
Also with the Epi-Lasik the epithelium of the cornea is first detached and, after the cornea is ablated, attached again to its previous location. The device used to cut the cornea is more blunt compared to the Lasik.
In contrast to Lasik, the other procedures mentioned cause considerably more pain after the operation, which gives Lasik an advantage in this regard.
Lasik as part of refractive Corneal surgery means laser in situ keratomileusis and is used to correct visual defects. myopia (Myopia) up to 8 dioptres, Farsightedness (Hyperopia) up to 4 diopters as well Astuteness (astigmatism) up to 6 diopters can be treated with Lasik. This procedure is based on the removal of deeper corneal layers using an excimer laser after folding back one Corneal lamella (Flap). This flap remains in contact with the cornea during Lasik and is placed back in its original position after laser treatment. A thorough examination of the eye - including the cornea and tear film production - is necessary before carrying out the procedure. Conveniently, the patient is pain-free very quickly after the operation and the desired visual acuity is achieved quickly within a few days. The invasiveness of the intervention and the resulting consequences such as increased risk of infection or incision errors have a disadvantageous effect. Occur as the most common complication dry eyes after a Lasik, which makes it necessary to use artificial tear substitutes twice (usually up to six months). Changes to the Cornea (deeper tissue, flap) as well as inflammation of various eye structures develop.
The result achieved with a Lasik with a maximum deviation of one diopter from the optimal visual acuity is the myopia (Myopia) 95%, in the Farsightedness (Hyperopia) at 91%. Alternative procedures include photorefractive keratectomy (PRK), the laser-epithelial keratomileusis (Lasek) and the epithelial laser-in-situ-kertomileusis (Epi-Lasik).
The cost of performing a Lasik is average 2000 euros per eye, whereby this price is subject to a strong fluctuation range. This must be borne by the patient himself, as the statutory health insurances do not currently cover the costs for the Lasik.