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Laser refractive surgery

By using state-of-the-art laser technology, we are able to correct nearsightedness, farsightedness, and astigmatism.

 

With the discovery of the medical use of the excimer laser we embarked on a whole new era in refractive surgery.  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 (PTK method).

The scheme of laser surgery 

a) at myopia b) at hyperopia c) at astigmatismus

 

It is possible to view laser surgery from two basic standpoints. Surgeries may be split into two groups – superficial or deep and standardised or individual. What are the differences and what is the optimal way of carrying out a surgery?

 

Superficial methods

These procedures come under many different names but in essence it is all about the removal or remodelling of the top layer of the cornea. The top layer of the cornea is called the epitel and it is continuously being renewed. When removed, the nerve endings in the cornea are bared. This leads to considerable pain but for instance under contact lenses, the surface heals with a new layer of epitel within 3-4 days. This regenerative property of the surface of the cornea is made use of in all types of superficial surgeries. It is the epitel that is manipulated with every time and the laser procedure is carried out beneath the epitel. Which procedures are these? 

 

Deep methods

 

Procedures are further divided into standardised (conventional) and individual.

The standardised (conventional) procedure refers to a surgery technique whereby different patients with identical dioptric problem undergo an identical procedure. This way it is possible to easily remove common sight issues such as short-sightedness, far-sightedness and possibly a combination of the two with symmetrical astigmatism. The remodelled surface is absolutely symmetrical similarly as in glass used in regular glasses. This technique assures high quality post-op results and has been in use for many years.


So what then is the individual procedure and why is it recommended? Simply put, this is a ‘tailor-made’ procedure using state-of-the-art technology.


The basis for the individual procedure is the utilisation of super precise pre-operation analysis of the eye. Through such analysis we find out the complexity of the impairment of each individual patient. Alongside impairment of the axis (short-sightedness and far-sightedness and astigmatism that may well be removed using conventional procedures, this method has the potential to remove also more complex abrasions and especially any present irregularities. What follows is the making of an operation plan with suggestions of corrections to the curvature of the cornea. Subsequently, the complete data is exported to the control unit of the laser.

This type of operation is currently carried out using exclusively a lamella created through femto technology. This technique has absolutely precise results. Once the lamella is lifted a system enabling precise eye measurement is activated. For the entire duration of the operation, reference points on the iris are continuously being compared. These reference points were acquired during the patient’s pre-op visit (it is the so-called iris map) generating points that are scanned using a special camera during the laser procedure itself. This ensures absolutely precise incidence of the excimer laser rays on the surface of the cornea even if the patient must continue moving his eye. The quality of the laser ray itself is of utmost importance. Upon incidence the ray must be capable of creating a perfect trail of different sizes. It is only in this manner that that an absolutely perfect correction of the cornea and the removal of all optical imperfections may be achieved. All of the above factors when combined ensure that the individual approach brings results exceeding 100% sharpness of eye sight. The individual approach is also known as LASIK VAWEFRONT,PRK- CUSTOM VUE,NEOLASIK HD,LASIK PREMIUM or iLASIK – iDESIGN.

 

PTK (Phototherapeutic 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.

 

PRK (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.

 

NO TOUCH

Is a „ super modern“ operating method whereby the epitel is not removed mechanically but instead is removed using the excimer laser in the first phase of the procedure. The problem with this procedure is that each individual patient has a different thickness of the layer of the epitel. It is impossible to measure this thickness upfront. The epitel is therefore removed based only on estimates and as such the final results are often lacking in precision. 

We do not carry out this procedure in our centre.

 

LASEK

The surface method of laser refractive surgery which is, in fact, a variant of the older PRK method. The covering surface layer of the cornea, i.e. epithelium, is not fully removed but only prepared as a thin flap after the application of a special solution. The laser surgery itself then removes a small layer of corneal stroma. At the end of the surgery, the epithelial flap is returned to its original place. Over the next few days, the epithelium will recover and regenerate. At the end of the operation, similar to the PRK method, it is necessary to cover the eye with a special contact lens to protect the eye during the first few days of recovery and alleviate pain. The lens usually remains in the eye for four days. Most people feel pain associated with the healing of the eye surface during the first few days. Eyesight recovery is also longer as compared to the LASIK method. The sight will usually stabilize within several months.

 

EpiLASIK

The surface method of laser refractive surgery similar to the LASEK and PRK methods. The surface covering layer of the cornea is cut off using a special “epikeratome”. The laser surgery itself then removes a small layer of corneal stroma. At the end of the surgery, the epithelial flap is returned to its original place. Over the next few days, the epithelium will recover and regenerate. At the end of the operation, similar to the PRK method, it is necessary to cover the eye with a special contact lens to protect the eye during the first days of recovery and alleviate pain. The lens usually remains in the eye for four days. Most people feel pain associated with the healing of the eye surface during the first few days. Eyesight recovery is also longer as compared to the LASIK method. The sight will usually stabilize within several months.

 

LASIK (Laser in situ Keratomileusis)

Is still the most precise and safest method and as such is currently the preferred method at all top centres worldwide.  The principle of the method consists in cutting away a narrow surface lamella of the cornea (most commonly 100-140 micrometers thick) and treatment of the tissue with excimer 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 process of the eye after a LASIK procedure is very fast (just a few hours) and basically painless. The post-op rehabilitation is more or less immediate and the eye is stabilised within a couple of days. This leads to only a minimal limitation of the patient’s activities post-op.  Currently we know LASIK in two basic forms. The difference is in the technology used to create the cornea lamella. The historically older method uses an appliance referred to as the mechanical microkeratome that is made up of two fundamental parts. The first part is attached to the surface of the eye so as to fixate it and prevent unwanted movement. The other part is then slid into the first part. It moves in a similar manner to a jack plane. A smooth cut is ensured by a fast moving (oscillating) razor blade. Safety and pretty good precision of the thickness and regularity of the lamella is ensured thanks to continuous enhancement in technology. This success rate of this method is directly dependent on the dexterity and experience of the surgeon. This procedure is also known as NEOLASIK or LASIK OPTIMUM at some refractive centres in the Czech Republic.

 
(videoreport HERE)

The Scheme of a refractive intervention using the Lasik method

a) cutting off the corneal lamella b) uncovering of the corneal lamella c) Laser-assistated remodeling of the stroma

 

 

 

d) resultant change in the cornal cuvature e) replacing of the corneal lamella f) final condition

 

FEMTOLASIK

The other option of creating a cornea lamella with the LASIK method is using the femtosecond laser – FEMTOLASIK (also known as intraLASIK, All-Laser LASIK, NEOLASIK HD, CRYSTAL LASIK,6D DIAMANT LASIK). The cutting of the lamella using a laser happens based on the principle of photo-disruption. The laser beam is focused on one point where the energy is concentrated and the tissue of the cornea immediately transforms into gas (it quite literally evaporates). This creates minute bubbles that further aid the process of tissue separation. The very best femtosecond lasers are capable of creating a point with a diameter of just 2 microns. The lamella creates in this manner is more perfect and smoother than when using the oscillating razor blade. Other advantage of this method is the possibility to also shape the edges of the lamella using special software and thus finding out just how well the lamella re-attaches itself into the original position. The eye is once again fixated using a suction ring and the laser beams fall on the cornea through an opening in a special cone.

ReLEX SMILE (NEOSMILE 3D,LASIK SMILE, LASIK FLEX)

It is a method using exclusively the energy of a femtosecond laser. It does not create a classic open lamella of the cornea but instead the femtolaser creates a sort of 3D lens deep within the cornea. It is subsequently freed from the surrounding tissue and removed from the cornea using pincers through an incision of about 3 millimetres. The result is the thinning and flattening of the cornea at its centre. As such this procedure is exclusively suitable for the correction of short-sightedness. The problem is that to date it is impossible to individually shape the cornea.
We do not carry out this procedure in our centre.

iLASIK – iDESIGN

In this sense, probably the greatest novelty in the Czech Republic is a method referred to as iLASIK - iDESIGN. This unique method is a fusion of the iDESIGN analysis of the eye and the iFS femtosecond laser combined with the excimer laser STAR S4 IR made by the renowned US company VISX.
The VSS technology (Variable Spot Size) uses software that enables combining of imprints of different sizes ranging from 0.65 mm to 6.5 mm throughout the procedure and their precise placement in the area using data compiled during the pre-op diagnostic examinations and using the iDESIGN analysis and thus carrying out an optimal photo ablation. The outcome is absolutely fantastic making this method the only one approved by specialist as suitable also for NASA pilots.



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