Laser eye surgery equipment

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Our clinic is the only one in the Czech Republic that makes use of the unique combination of the iLASIK procedure with the iDESIGN technology. This method guarantees precision, safety and long-term stability of vision that exceeds the boundary of 20/20 (100% vision). Our aim is not simply to just remove dioptres, but to improve the patient’s vision to the maximum.

This unique laser system is the combination of three individual units:

  • iDesign
  • Femtosecond laser iFS®
  • Excimer laser VISX STAR S4 IR

iDesign®

iDesign represents the combination analysis of 5 measurements* of the basic parameters of the eye in a single instant. At the same time, it creates a proposal of an optimised surgical procedure tailor-made to the specific needs of the patient being examined and transfers the created surgery plan into the memory of the VISX STAR S4 IR laser. The laser subsequently executes the required change to the curvature of the cornea. 

A scan of the patient’s iris is performed simultaneously during the examination using the iDesign® system. This scan forms the basis for the identification and monitoring of the iris as part of the Automated Iris Registration (see VISX STAR S4 IR). This ensures that it is impossible to confuse patients and his/her eye to be operated because the iris scan is absolutely unique (similarly as a fingerprint). During the surgery, a special camera constantly compares pre-set reference points on the iris that were acquired during the examination using iDesign® with points that are being read while the laser procedure is taking place. In case of necessity this ensures diversion of the laser beam to the correct spot and as such guarantees that the planned changes to the shape of the cornea will be executed precisely.

*Utilisation rate of a single image – a total of 5 measurements:
  • Aberrometry (Wave front analysis)
    Hartmann-Shack Wave front sensor with high resolution (5x higher resolution than the previous version of the WaveScan) and Fourier reconstructive algorithm, utilising more than 1,257 analysis in 7 mm zone increase the precision of the measurements. 
  • Refraction of the eye (dioptre properties of the eye as a whole)
  • Pupillometry (measuring of the width of the pupil under different light intensity)
  • Keratometry (measuring dioptre refraction of the cornea)
  • Topography of the cornea (map of the cornea)

iFS® Femtosecond laser

Femtosecond lasers are used in ophthalmology when operating refractive errors, when operating the cornea and when operating the pupil. Femto-laser is one of the so-called solid-matter lasers. It works with ultra-short optical impulses with wave-length range of 1,100–1,600 nm. The advantage of this type of laser is great precision.

The laser incision happens based on the principle of photo-disruption. The laser beam is aimed into a single point where the energy is concentrated, and the tissue of the cornea immediately converts to gas. Tiny bubbles are formed and these help with the tissue separation. An important parameter of a laser is frequency with which the laser is able to generate laser pulses. A higher frequency of the pulses using lower energy, aimed with great precision, lead to the possibility of overlapping of individual points and thus eliminating the so-called tissue bridges that reduce the quality of the laser incision. It thus applies that the higher the frequency of the laser, the more technologically advance the device is.

Uses of Femtosecond laser iFS®:
  • Corneal lamella

During the first phase of a laser eye surgery, a thin lamella (flap) is created. The flap is then lifted and during the second phase of the surgery, using an excimer laser, the definitive correction of the curvature of the cornea is carried out. iFS® lamella is far more precise than with different devices of similar type. It cannot be compared in quality to the quality of the lamella created using mechanical microkeratome. 

• It reduces or eliminates entirely any complications – during the process of creating the lamella as well as in the post-surgery phase.
• Tighter separation between the points creates a smoother surface of the stromal bed and enables effortless lifting of the created corneal lamella.
• Software enables to individualise the parameters of the corneal lamella. It is possible to change not only the shape (for example to an elliptical shape where there is higher astigmatism) but also the angle of the side incision up to 150°. This ensures greater post-surgery stability of the flap, improved regeneration of the disturbed nerves and lesser incidence of symptoms of the dry eye syndrome.

  • Corneal tunnels

Corneal segments, also known as rings, are used in patients with keratoconus. These rings are inserted into corneal tunnels so as to flatten the cornea and femtosecond laser is far more precise and as such the surgery as a whole is safer than when using manual techniques. 

  • Corneal pockets

Some special implants are placed in corneal pockets, for example micro-lens for the correction of presbyopia or a ring (MyoRing) for the flattening of the cornea with high astigmatism or pro keratoconus.

  • Astigmatism correction

Here the laser is replaced by a diamond scalpel. It is used to create incisions in the cornea that correct its irregular curvature. The precision is better than in incisions made by the hand of the surgeon.

  • Keratoplasty

Femtosecond lasers are also used in transplantation of cornea. Due to higher precision, the healing time is reduced, and we are able to create a more precise shape of the transplant. A good example is lamellar keratoplasty (DSAEK), where only a part (lamella) of the cornea is replaced. Femto-laser creates a corneal target from the donor tissue as well as from the tissue of the recipient. The procedure is similar also in cases where the cornea is being transplanted in its full thickness, the so-called. Penetrating Keratoplasty of the cornea (PKP).

Excimer laser VISX STAR S4 IR

The essence of laser surgery is the re-modelling of the tissue of the cornea through the effect of the excimer laser depending on the dioptre error. The laser beam with a wavelength of 193 nm (UV) can, upon its incidence on the cornea, gently remove a pre-determined thin layer of tissue. The energy of the laser radiation disturbs the connection between the individual molecules of the corneal tissue and leads to their evaporation (vaporisation). Each pulse of the excimer laser is capable of removing corneal tissue with the precision of 0.25 microns. The distribution and size of the laser pulses is controlled by a computer and the required curvature of the cornea and thus a change of its optical robustness is achieved by the gradual lowering of the tissue. 

With short-sightedness, the cornea is flatter in its central part and as such is less refractive. With far-sightedness it is the opposite. Here, the aim of the procedure is to steepen the cornea and increase its refractivity. With astigmatism, the error is corrected by smoothing-out the irregular curvature of the cornea.

Because the excimer laser produces cold radiation, there is no danger of heat induced damage of the corneal tissue or any other structures within the eye. High precision and good predictability of changes in the surface curvature and its safety make excimer laser procedures one of the top-ranking methods in refractive surgical methods. Excimer laser can be used also to remove surface scars on the cornea (PTK).

The laser that we use, namely the VISX STAR S4 IR is one of the top argon-fluoride excimer lasers. With this system, the emphasis is on the gentleness of the procedure and its precision. The VISX STAR S4 IR can be used for the PRK surgery method and also for the LASIK method. In combination with the iDESIGN system, it represents the perfect individualised technology of dioptre error removal.

A modern laser procedure should remove minimal amount of corneal tissue, shorten the time of exposure of the corneal tissue to the minimum and ensure good vision even at dusk or in the dark. The VISX STAR S4 IR system manages all of the above excellently.

The used technology VSS (Variable Spot Size) enables the combination of trails in the range from 0.65 mm to 6.5 mm throughout the procedure with precise placement in the space based on processing the information acquired from the diagnostic pre-surgery examinations (iDESIGN, topography). The 0.65 mm diameter of the beam is used for the precise smoothing-out of slight curvature nuances in the cornea in tailor-made ablations. The duration of one laser pulse is 20 ns. This is how a truly minimal amount of tissue is removed using minimal temperature changes and the reduction of the overall duration of the procedure is achieved.

VISX S4 standardly works with an optical zone of 6.5 mm. This may be widened up to 8 mm based on individual needs of different patients. The maximum diameter of the treated area (ablation zone) can, however, be up to 9 mm. Using a greater optical zone in the area of the ablation lessens possible problems with night vision due to the natural widening of the pupil in times of worse light conditions. 

Other unique systems used in the VISX S4 device:
  • iDESIGN – individualised laser correction is a method developed by the VISX company. With this technology, VISX brings us perfectly precise measurements and the possibility to provide tailor-made corrections based on the needs of the individual patients. 
  • Active Track Automatic Centring – enables observation of the centre of the pupil during the procedure and its automatic centring onto the centre of the optical axis of the laser system. The frequency of scanning is three times higher than the frequency of the pulse and as such it safely records movement in-between the individual pulses.
  • Automated Iris Registration (IR) – enables precise measurements and eliminates mistakes associated with movement of the eye that may happen when the patient changes position even ever so slightly or when the eye blinks. Throughout the entire procedure, a special camera compares reference points on the iris acquired during the iDesign examination with points scanned during the laser procedure and as such it can ensure the deflection of the beam of the laser in the correct spot.

The combination of the above-mentioned systems registers, with the use of two infra-red video cameras all movements of the eye in the X – Y and Z axis. Due to this fact, the surgical procedure is absolutely precise, and it is possible to reach vision exceeding 100%.