LASIK – Laser in situ keratomileusis for the treatment of refractive errors (LASIK eye surgery) - Ophthalmology

LASIK (laser in situ keratomileusis) is an eye surgery that can correct various types of vision problems. The procedure can be a viable alternative to contact lenses or glasses for people with farsightedness or nearsightedness. Of course, patients should be aware of the benefits and risks associated with LASIK surgery. It is an outpatient procedure performed using anesthetic eye drops.

Experts have been performing LASIK surgery since 1990. Using a laser, doctors remove corneal tissue, thereby altering the curvature of the cornea.

Because the procedure takes place beneath the surface of the cornea, patients can regain sharp vision relatively quickly and painlessly. However, the incision made in the cornea does pose a higher risk to patients. The goal of this surgical method is to correct refractive errors. In the best-case scenario, patients can subsequently manage without artificial visual aids.

The cornea and the lens of the eye refract incoming light through their curvature and project a sharp image onto the retina. In cases of refractive errors (nearsightedness, farsightedness, and astigmatism), the focal point is not on the retina but in front of or behind it.

LASIK laser eye surgery can correct these vision problems quickly, with few complications, and painlessly. The curvature of the cornea can be altered by removing tissue. This adjusts the refraction of light and the focal point. Using a laser, doctors precisely control the removal of tissue down to the micrometer range. This is why the procedure is so reliable.

The LASIK procedure has been in use since 1990. During the procedure, experts use a corneal microkeratome or a femtosecond laser to cut a thin flap into the cornea. They lift this flap so that the laser can ablate the underlying tissue.

Illustration of refractive errors (https://commons.wikimedia.org/wiki/File%3ARefractive_errors.jpg)

 

Applications of LASIK

The LASIK method is suitable for the following diopter ranges and conditions:

• For the treatment of nearsightedness up to a maximum of -10 dpt.

In nearsightedness, the eyeball is too long. As a result, the sharp image of distant objects is focused in front of the eye’s retina. For clear vision, the focal point of the light rays must therefore be further back. This requires flattening the cornea.

• For the treatment of farsightedness up to a maximum of +4 dpt.

In hyperopia, the eyeball is too short, so the focal point is located behind the retina rather than on it. To increase the refractive power, the laser removes corneal tissue in the periphery.

• For the treatment of astigmatism up to a maximum of 6 dpt.

Due to the distorted cornea, incoming light does not converge at a single point on the retina.

• For the treatment of presbyopia up to a maximum of +3/-5.

In this procedure, the lower part of the cornea is ablated to simulate the effect of reading glasses.

For higher degrees of refractive error, there are various other procedures, such as an implantable contact lens (ICL).

The degree of refractive error for which LASIK is used varies from clinic to clinic. The German Ophthalmological Society recommends LASIK for nearsightedness up to minus ten diopters.

The LASIK method is not suitable for every person with a vision defect who is interested in the procedure.

The basic requirements are:

• a minimum age of 18
• a refractive error that has remained stable for two years
• a minimum corneal thickness to ensure corneal stability. After the procedure, the cornea must retain a certain residual thickness.

LASIK surgery is not suitable for:

• Keratoconus: This is a progressive thinning of the cornea.
• Glaucoma
• Collagenoses
• Wound-healing disorders
• Autoimmune diseases such as rheumatism
• Patients who do not have stable vision.
• Cataracts
• Pregnancy
• Allergies to necessary medications

Even if the patient must take contraindicated medications, LASIK surgery is not possible.

Because every patient has different expectations regarding this procedure, a detailed consultation with the doctor beforehand is essential.

Several examinations are necessary before the actual procedure:

1. First, a thorough eye examination is performed. The goal of this examination is to determine the current degree of refractive error. To ensure accurate results, two examinations should be conducted two weeks apart.
2. In addition, as part of the preoperative examination, the doctor measures the thickness of the cornea using a device called a pachymeter. Determining the thickness of the cornea is important because the cornea has a significant influence on intraocular pressure.

The cornea must be thick and stable enough to undergo the procedure. If the patient’s cornea is too thin, any responsible doctor will refuse to perform the surgery for safety reasons. Provided the requirements for the procedure are met, you can wait until one eye has regained full visual acuity. The preliminary examinations serve both to collect the specific data needed for treatment and to determine whether there are any contraindications.

The patient should stop wearing contact lenses for about two weeks before the preliminary examination.

In addition to measuring corneal thickness, further examinations should be conducted beforehand:

• corneal topography to determine the curvature of the cornea
• measurement of pupil size
• a tear film assessment
• measurement of intraocular pressure
• a general ophthalmological examination, as well as
• a medical history

The latter is necessary to gather information relevant to the procedure.

https://commons.wikimedia.org/wiki/File%3AOphtalmic-femtosecond-laser.jpg

• At the beginning of the procedure, the doctor administers a local anesthetic to the eye.
• The doctor then inserts an eyelid retractor, which holds the eye open as wide as possible.
• Next, the femtosecond laser or the corneal microkeratome cuts a thin flap into the cornea, which remains attached to the eye. The corneal shaper consists of a suction ring, which serves to stabilize the eye, and a movable cutting head. During the procedure, intraocular pressure rises sharply, leading to a temporary loss of vision. However, vision returns immediately once the doctor has made the incision.
• The doctor then lifts the flap and measures the thickness of the remaining cornea. Patients generally hardly notice the subsequent treatment with the excimer laser, as the laser light has a wavelength of 193 nanometers and is therefore in the invisible spectrum.
• As soon as the laser treatment is complete, the doctor rinses the treated area and folds the corneal flap back into place. Thorough rinsing is important to remove any foreign particles.

In recent years, treatment with the femtosecond laser (FEMTO-LASIK) has become increasingly common, as this procedure is significantly safer. If the laser incision is not made correctly, the treatment can be stopped and repeated at any time. If the procedure is interrupted, no damage to the cornea results.

Laser surgery offers the advantage of extremely precise incisions. The cornea usually heals within two days. However, healing of the entire incision site can take up to several months. The following video demonstrates the LASIK procedure:

One of the biggest advantages is that patients experience very little pain during and after the surgery. In addition, the treated area heals extremely quickly. Compared to implants, there is also a significantly lower risk of infection. On the other hand, there are some disadvantages to the LASIK procedure.

For example, the procedure causes destabilization of the cornea. The extent to which the vision defect can actually be corrected depends on the size of the pupil and the thickness of the cornea. Many patients find it uncomfortable that their eyes are very dry after the procedure. As some studies show, the desired correction of the vision problem can be achieved in about 80 percent of patients.

Complications are very rare and occur in less than one percent of LASIK surgeries. However, problems can arise after the procedure. As a general rule, the higher the diopter value to be corrected, the greater the likelihood of side effects.

The following complications are possible:

• Impaired vision at dusk or in the dark
• Reduced contrast sensitivity
• Glare, halos, or light halos: The latter affect vision by causing visual disturbances in the field of vision
• Overcorrection or undercorrection due to a renewed change in refractive error
• Perception of double images and double contours: This often leads to dizziness and balance disorders.
• The weakened cornea may become unstable under certain circumstances and, as a result, bulge outward (keratectasia). This leads to a deterioration in vision and, in the worst-case scenario, requires a corneal transplant. However, this happens very rarely.
• The flap may also shift in the first few days after the procedure. This is caused by external factors such as rubbing the eyes.
• Tissue cells may grow under the flap, causing cloudiness. In both cases, another surgery is necessary.
• One of the most common side effects of LASIK treatment is dry eyes. It affects 15 to 20 percent of patients. The cause is reduced tear production, as the corneal nerves can no longer detect when the corneal surface is dry.
• Some patients also complain of glare at night and at dusk.

Both the dryness and the glare subside in 95 percent of patients within the first three months. However, if the refractive error was 5 diopters or more, sensitivity to glare may be permanent. This can result in the patient being unable to drive at night.

Prices for LASIK eye surgery have fallen sharply in recent years. They vary from provider to provider. In Germany, the procedure costs at least 1,000 euros per eye. Added to this are the costs for various examinations.

Public health insurance plans generally do not cover the costs of this procedure. For privately insured patients, it is worth speaking with their insurance provider: private insurers evaluate each case individually. In any case, it is possible to claim the costs of laser treatment as a tax deduction. It is recognized as an extraordinary expense.

With a probability of more than 90 percent, visual acuity after the surgery is 0.5 diopters above or below the target value. 

More than 90 percent of patients are able to get by without glasses or contact lenses after the procedure. In more than 80 percent of cases, patients achieve uncorrected visual acuity of 100 percent or better.

In five to ten percent of patients, residual refractive error persists after treatment. Doctors can correct this with a follow-up procedure.

However, there is no guarantee that the vision correction achieved through LASIK will last a lifetime. Vision may deteriorate again over the course of a person’s life due to natural causes.

LASIK treatment is now an established method of refractive surgery and enables many patients to live without glasses. During LASIK, the cornea is precisely reshaped using laser in situ keratomileusis to optimize refractive power. LASIK surgery typically takes only a few minutes per eye and is often performed on both eyes simultaneously. During the procedure, a flap is created using a microkeratome or femtosecond laser, and the underlying tissue is reshaped with an excimer laser. The corneal flap is then repositioned, allowing for rapid healing.

Refractive errors are corrected by specifically altering the curvature of the cornea, which can significantly improve visual quality. Especially in modern ophthalmology, the LASIK procedure is considered precise and safe, provided that certain requirements—such as sufficient corneal thickness—are met. Alternatives such as LASIK and LASEK or LASEK and PRK may be considered if the cornea is too thin or if LASIK is not an option.

A comprehensive preoperative examination by an ophthalmologist is crucial before any LASIK surgery. During this examination, the retina, corneal tissue, and eye movements, among other things, are assessed. Factors such as being at least 18 years old or having individual risk factors also play an important role, as the surgery may otherwise be declined for safety reasons.

Costs, such as € per eye, vary depending on the provider—such as Care Vision—and the technology used, though not all health insurance plans cover these costs. Overall, laser eye surgery represents a long-term solution for many people, particularly LASIK for nearsightedness. Despite modern technology, a follow-up correction may be necessary in some cases. Traditional LASIK techniques and laser-assisted procedures have permanently transformed eye surgery and offer an effective way to correct refractive errors.