LASIK

The laser in - situ keratomileusis (LASIK ) is an eye surgery to correct refractive errors of optical. You may be weighing the pros and cons as well as the existing risks represent an alternative to glasses or contact lenses. The surgery is currently the most widely used method within the refractive surgery.

Basics

In this applied since 1990 laser procedure is accomplished a change in the corneal curvature by resection of tissue in the cornea. The tissue ablation of the cornea is indicated by the cutting and opening of a blade, the so-called Flap possible. A LASIK patient has very quick and relatively painless sharp vision, as the operation is performed under pain-sensitive corneal surface and has the epithelium in contrast to the surface treatments (PRK, trans - PRK) re-grow, not only. Through the operation-related corneal incision ( flap ), however, results in a higher risk potential.

The LASIK offers the chance to correct refractive errors, but is also usually a surgical procedure on a healthy organ in principle dar. In the best case, the remaining refractive error less than ± 0.5 diopters and the patient can see without visual aids (glasses, Contact lens ) live. The uncorrected visual acuity, that is, the visual acuity without aids, improves dramatically usually achieved and ideally 1.0 or more. The best corrected visual acuity ( visual acuity with optimal spectacle correction ), however, remains ( depending on the treatment method) usually unchanged or slightly changes.

Treatment area and contraindications

The LASIK procedure is considered indicated for the correction of:

• Myopia up to max. -10 diopters
• Hyperopia up to max. 4 diopters
• Astigmatism up to max. 5 diopters

These limits can vary from one to two diopters higher or lower depending on your country, clinic and used laser system. The German Ophthalmological Society (DOG) classifies example the LASIK for myopia up to -10 diopters and astigmatism up to 3 diopters " scientifically recognized " as a.

Contraindications are circumstances that prohibit a LASIK treatment or only allow a careful consideration of the risks. An essential prerequisite for a LASIK treatment is a sufficiently thick cornea. Too thin cornea is regarded as strict contraindication. The limit applies a residual thickness after treatment of at least 250 microns. This residual thickness is calculated from the corneal thickness minus the flap thickness and the maximum excavation depth. LASIK should not be performed when chronically present progressive corneal diseases. In particular, in keratoconus prevents its treatment, since the cornea is further weakened and the disease would worsen dramatically. If the refraction of the patient is not stable, which means the soft refractions in a relatively short time intervals significantly from each other, no LASIK treatment should be carried out. Contraindications continue the eye disease glaucoma with visual field damage and symptomatic cataract apply. Systemic diseases that exclude a LASIK treatment, are collagen vascular, autoimmune diseases and wound healing. Finally LASIK patients should be at least 18 years old.

Preliminary

The expectations on treatment outcome are very different from patient to patient and should be discussed in advance extensively with the attending physician.

First, in addition to a detailed specialist medical eye examination is the determination of the actual refractive error in the foreground. The refraction should be performed at least twice at an interval of at least 2 weeks. This should be done by an experienced ophthalmologist or an optometrist, a refraction with an autorefractor is insufficient in any case. Further the corneal thickness, are found mostly with the help of a so-called pachymeter. Since, the short-sighted, the patient is more cornea has to be removed, it is essential that this is also thick and sturdy enough for the planned surgery. If too thin cornea, the responsible doctor will reject the operation for security reasons. If the thickness is sufficient, however, it is sufficient as a precautionary measure during surgery completely off, wait after surgery of the first eye until the visual performance of the corresponding eye has returned to normal. Next, a sufficient distance between consultation and the operation performed is just recommended to allow the patient sufficient to think about the risks of eye surgery.

The preliminary investigations serve on the one hand, to capture the correct treatment data, to exclude contraindications but on the other hand. The patient should not wear contact lenses at least two weeks before the preliminary studies.

Total following analysis should be performed prior to the operation:

• Determination of corneal thickness with an ultrasonic pachymeter or anterior chamber OCT
• Corneal topography to determine the curvature of the cornea and detecting Hornhautirregularitäten
• Measurement of pupil size ( pupillometry )
• Measurement of intraocular pressure
• Tear film destination
• General ophthalmological examination including slit-lamp examination
• Case history

Course of treatment

First, the eye is numbed with drops and a local eye speculum is used, which keeps the eyes wide open. With a microkeratome ( Callus ) or a femtosecond laser (so-called Femto- LASIK) is a thin lamella cut (diameter about 8 to 9.5 mm and thickness between 100 to 160 microns ) in the cornea. (Hereinafter flap ) this plate is not completely separated, but maintains a connection to the rest of the cornea, which serves as a " hinge ". This " hinge " is now mostly superior ( ie above), but occasionally also placed nasally ( toward the nose ) (partly depending on the microkeratome ).

The microkeratome is usually made of two parts, a suction ring for fixation and a movable cutting head moves with an oscillating blade over the eye. During the Mikrokeratomschnitts the eye temporarily loses his sight, since the intraocular pressure increases strongly, and the optic nerve ( optic nerve ) pulls the trigger. The cut is done in a few seconds and the vision returns immediately.

The right retrievable video shows a typical LASIK with a microkeratome. The eye is kept open by a lid retractor and the area surrounding the eye is sterile covered. Before the microkeratome, the cornea is marked asymmetrically in order to position the flap in case of a complication again correctly. The suction ring of the microkeratome is then placed centrally on the eye and used the microkeratome itself. A rapidly oscillating the microkeratome blade performs the forward motion, and thus cuts the flap (in this case, superior).

After the cut, the flap is then opened and measured by Ultraschallpachymeter the remaining corneal thickness to determine if the flap had the desired thickness. In flap open is ensured before the actual treatment that is uniformly dry surface to be treated. If this were not the case, it come due to the strong absorption of the Excimerlichts in water, in an uneven tissue removal would.

The excimer laser treatment itself is hardly noticeable because the light of the excimer laser is invisible with its wavelength of 193 nm. One only sees slight shape changes on the treated surface of the cornea.

After the laser ablation, the treated area is rinsed and the flap folded back, with further rinsing. Thoroughly rinse is important to remove any foreign objects ( Abtragsreste, epithelial cells) from the area between flap and cornea (called the interface). Using a small sponge the excess liquid is sucked from the interface and the flap smoothed. So that the treatment is complete and the lid retractor can be removed.

The flap creation with a femtosecond laser is a growing by over mechanical microkeratome. He offers several advantages, in particular the greater security. If the laser cut is not performed correctly, the treatment can be repeated after each case or aborted safely. Since the laser perforation of the tissue with tiny bubbles, always tissue bridges left behind, which must be separated with a suitable instrument the doctor to completely separate the tissue. One can imagine that in some way the perforations on stamps, in which an effort is necessary in order to separate them, but the separation is exactly at the specified location. The physician decides therefore to stop treatment, the bubbles produced are absorbed by the tissue and the cornea is virtually intact. A special technique of corneal flap separation is called Flaporhexis. It reduces the mechanical stress of the corneal flap when separating from the corneal stroma, leaving the central area on the entrance pupil free from contact with an instrument. This provides the perfect environment for an uninfluenced by mechanical instruments wavefront- guided ablation with the excimer laser represents a further technique of corneal flap separation is known as sat -opening ( " Scharnieröffner ").

Another advantage is the precision of the cut, which ensures that the flap with high accuracy, the preset dimensions. In particular, the thickness of the flap is much more precise and allows cutting significantly thinner flaps (minimum 80 microns ). The treatment using a femtosecond laser is often referred to as LASIK surgery, but is from a medical standpoint, does not constitute a difference to the normal LASIK

After a successful flap cut is this, including the pain-sensitive epithelium, folded to the side and performed on the underlying tissue, the laser treatment. The duration of the laser irradiation is determined by the amount of correction and the treatment diameter, but is advanced lasers usually less than 30, a so-called eye-tracking system S. In the following the treatment of eye movement and guides the laser beam by these movements. After the laser treatment, the flap is folded back to the original place back, rinsed the area between the flap and corneal thoroughly and carefully positioned the flap. Is the doctor satisfied with the Flapposition, he removes the lid retractor and the patient can close his eye. The epithelium heals on the edge of the flap independently within one to two days. However, a firm adhesion of the entire cut surface takes several weeks to several months to complete.

Pros and Cons

Advantages of LASIK:

• Little pain during and after the operation.
• Very rapid recovery of vision, the treatment outcome is practically experienced immediately after the procedure.
• Compared with implants low risk of infection.
• There are many years of experience in front of millions worldwide operations.

Cons:

• The structure of the cornea is destabilized.
• The flap brings various risks (see risk).
• The maximum correction is dependent on corneal thickness and pupil size.
• Dry eyes are common.

Due to the constant evolution of technology are older or long-term studies for LASIK meaningful only conditionally. Improvements such as better tracking systems and optimized ablation profiles have not yet been included in these studies. Modern treatment methods and the increasing experience of the operators provide a high degree of predictability. Approximately 85 % of patients are in the range of ± 0.5 diopters.

In a study of LASIK over a year achieved 78% of patients the desired correction (± 0.5 diopters, some with two OPs). After twelve months, only 5 % had night vision problems. Approximately 94 % had after this year the same or better uncorrected visual acuity. Very detailed study results presented the U.S. Food and Drug Administration ( FDA) on its website. These studies are carried out under the approval procedures for refractive laser devices and are considered very reliable. You will be closely monitored and conducted in parallel at several clinics.

Risks

As with any surgical procedure, there are a number of risks, in the LASIK. The type and frequency of occurrence depend, among other things, on the experience of the surgeon, the amount of correction, the technique used, and individual factors.

General risks that are inherent in both the LASIK, but also for any other type of refractive surgery, limitations of the twilight and night vision due to reduced contrast sensitivity, glare (specular effects) and Halo Gone are ( halos ). Occurrence can also short-to long -term over-or undercorrection, and a reduction in visual acuity with optimal spectacle correction (so-called best corrected visual acuity ). Infections of the eye are in any type of treatment, but particularly with implants, possible.

The risk of impairment of vision after LASIK treatment also depends on individual risk factors (such as the number of diopters, flat cornea, pupil size). In addition, the experience of the surgeon has a serious impact on the complication rate. A study from 1998 comparing the intraoperative complication rate of the first 200 treatments of an operator with the following 4800 treatments. In the first 200 treatments, the rate is 4.5 %, with the other treatments only at 0.87 %.

A very serious risk is the structural weakening of the cornea after Gewebsabtrag. This weakening and the constantly acting on the cornea intraocular pressure can cause a bulging of the cornea ( corneal ectasia ). The risk of this increases with decreasing residual corneal thickness after treatment. The minimum value for the residual thickness of 250 microns is. The residual thickness is calculated from the central corneal thickness minus the flap thickness and the central tissue removal. Furthermore, appear to play a role in Keratektasien genetic factors.

Brings particular, by cutting the flap LASIK method a number of risks. In the first few days after treatment, there may be a discomfort to the cornea. Very often, in 15-20 % of cases, dry eyes occur in the first weeks or months after treatment. The cause of dry eyes is in the severing of corneal nerves by the flap incision. The severed nerves can no longer discern the desiccation of the corneal surface and tear production and eyelid blink be reduced. For patients with chronic dry eye, the probability of re- deterioration increased.

The cutting of the flap is in particular in the use of a microkeratome, a serious risk represents the desired shape and size of the flap will not be obtained and, in rare cases it can also lead to incomplete or perforated flaps. Another risk is the ingrowth of epithelial cells under the flap. This lead to cloudiness in the affected area, but are relatively easy to remove from the doctor. The flap can be moved after the treatment by strong external influences, or even separated. Such risks are particularly at sports or car accidents. Finally, when LASIK is a risk of ectasia and occurs in a much higher degree than in the PRK, because the cornea is further weakened by the flap incision.

Since the first LASIK treatments were not performed until 1990, there is naturally no longer-term insights into their possible long-term consequences. At approximately <1 % of all patients of LASIK complications occur during surgery. The flap holds after surgery mostly on adhesive forces. The raising of the flap itself is still possible after seven years. The flap is normally extremely stable. Rarely are dislocations with little external influence (rubbing on the eye, contact lenses). More common are these due to sports injuries (about ball inside the eye), contact with pets or car accidents with airbag deployment. Only with proper treatment by a specialist, an acceptable visual acuity can be prepared in case of accidental again.

Proof of quality

The objective evidence of quality is very important for patients. There are several certificates that are used in health care.

QM certificate according to ISO 9001:2008

The ISO 9001: 2000 certificate is a pure process-oriented quality management Seal, which is awarded across industries. It reflects process quality and says nothing about the quality of medical treatment or the technical status of the instruments deployed from.

LASIK -TÜV

Especially for laser eye centers there since 2006, the so-called LASIK -TÜV, which is based on the ISO 9001: 2000 certificate. It is offered by TÜV SÜD and was developed in collaboration with the Commission Refractive Surgery ( KRC ), the Association of Specialty Clinics for Eye Laser and Refractive Surgery ( VSDAR eV ) and the Professional Association of Ophthalmic Surgeons ( BDOC ) was developed. In contrast to the ISO 9001: 2000 Certificate of LASIK - TÜV tests not only the process quality but also the service and quality of results. Specifically, the following aspects are examined: