By using state-of-the-art laser technology, we are able to correct nearsightedness, farsightedness, and astigmatism.
The effect of an excimer laser
The principle of a laser surgery is the re-modelling of the corneal curvature using a laser beam. The laser beam, with a wavelength of 193 nm, that falls on the corneal surface is able to gently remove a very thin layer of the tissue that was specified in advance. The energy of laser radiation can interrupt the link between individual molecules of the corneal tissue resulting in the evaporation of the molecules. Every impulse of the excimer laser is able to remove the corneal tissue at an accuracy of 0.25 micron. The distribution of laser impulses is controlled by a computer via screens, and the gradual removal of the tissue results in the required modification of the corneal curvature and it also alters the corneal optical power.
In a nearsighted eye, the cornea is flattened in the central part, becoming less refractive while in a farsighted eye, the procedure makes the cornea steeper thereby increasing its refraction. Astigmatism is an eye defect that is corrected by reshaping the irregular corneal curvature so it becomes more spherical and uniformly curved. Since the excimer laser produces “cold” radiation, there is no risk of thermal injury to the corneal tissue or to any other eye structures. Thanks to high accuracy, good predictability of changes in the surface curvature and high safety, excimer laser procedures are currently among the leading refractive surgical methods. The excimer laser can also be used for therapeutic reasons, for example for the removal of surface scars on the cornea.
The scheme of laser surgery
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| a) at myopia |
b) at hyperopia |
c) at astigmatismus |
PROCEDURES OFFERED AT OUR CENTRE
LASIK method
( Laser in Situ Keratomileusis) is more recent and advanced method that is currently preferred at all leading centres where it is used to treat short-sightedness, mild and moderate far-sightedness, and astigmatism. The principle of the method consists in cutting away a narrow surface lamella of the cornea (most commonly 160-180 micrometers thick) and treatment of the tissue with laser after the lamella has been lifted off. After the deeper layers have been treated the lamella is returned back to its original site. It takes just a few minutes for the lamella to reattach and there is no need for sutures or covering the surface of the eye with a contact lens. The healing after the LASIK procedure is very rapid and practically without pain, the rehabilitation of vision lasts several days making early surgery on the other eye possible, while the limitation of patient activities in the postoperative course is minimum. LASIK is thus a method that si more demanding in terms of its overall procedure and demands also better technical equipment of the centre as well as a higher degree of experience of the surgeon, but the high precision of the method, the good postoperative stability and painlessness of both the surgery and postoperative course explain why the method is preferred to PRK.
The Scheme of a refractive intervention using the Lasik method
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a) cutting off
the corneal lamella |
b) uncovering of
the corneal lamella |
c) Laser-assistated remodeling
of the stroma |
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d) resultant change in
the cornal cuvature |
e) replacing of
the corneal lamella |
f) final condition |
PRK method
(photorefractive keratectomy) is a method consisting in a modification of the curvature of the corneal surface after removing its surface cellular level-epithelium. The surface of the cornea is first anaesthetised using a topical anaesthetic administered in the form of drops and the epithelium is then removed. This is followed by the laser procedure carried out in the surface layer of corneal stroma. As the epithelium layer forms a protective cover without which the eye becomes rather sensitive and even painful, the cornea must be covered with a contact lens after the procedure. Regeneration of the covering epithelium layer occurs within several days but even so the first days of the healing process of the eye are accompanied by pain and fuzzy (blurred) vision. Definitive healing of the cornea and stabilisation of vision vary to a large degree and can be expected to take several weeks to months. At present, PRK is an alternative to LASIK and i used to treat mild and moderate forms of short-sightedness.
Astigmatic keratotomy
Is a microsurgical method appropriate for the treatment (reduction) of astigmatism. The method consists in placing two arcuate incisions at the border of the cornea using a special diamond knife (blade). Varying the length, depth and location of the incision the surgeon can achieve the required change of the corneal curvature and thereby correct the astigmatism. For higher degrees of astigmatism and combined refractive errors, a combination of this procedure with LASIK can be considered. As a first stage, the incision are used to reduce corneal astigmatism, and the residual error is than approached-after the first incision have healed and refraction has stabilised (about 6 months after the incisions)-with a laser procedure.
PTK method
Photo-therapeutic keratectomy – is a laser therapeutic procedure to treat corneal surface diseases, for example recurrent erosions, corneal scars, etc. The course of the procedure and postoperative recovery are similar to those for the PRK technique. The procedure is based on the laser ablation of corneal surface layers after the covering epithelium has been removed. The procedure is performed under local anaesthesia using anaesthetic eye drops, and takes about 5 minutes. Following the procedure, a therapeutic contact lens will be applied on the eye and it remains there for 3-4 days until the cornea has healed completely. The patient has to apply antibiotic drops over this period of time. The eye may hurt. After the removal of the therapeutic lens, the patient will continue to apply anti-inflammatory eye drops.