Laser eye surgery is part of the field of refractive surgery. This includes eye operations in which the overall refractive power of the eye is changed in order to compensate for visual defects. Surgical eye correction allows patients to dispense with glasses or contact lenses or reduce their required strength. Here you will find further information as well as selected laser eye specialists and centers.
With short-sightedness, those affected see objects close up sharply, while objects in the distance appear more or less blurred.
With short-sightedness, the focal point of the eye is in front of the retina. This means that the eye is relatively too long for the refractive power of the cornea, or the cornea is too curved for the anatomy of the eye.
There are various surgical procedures for myopia. If myopia is not too pronounced, it can be corrected by refractive surgery using a laser.
Artificial lenses can be implanted in the eye for very severe short-sightedness. These are usually implanted in addition to the patient's own lens.
Farsighted people see objects in the distance sharply, while objects close up appear blurred. The eye must accommodate the lens in order to see objects close up clearly. This means that the eye muscles deform the lens and "focus" on the closer objects.
As a result, farsighted people often find seeing strenuous. Young people can often compensate for farsightedness through accommodation.
If the lens's ability to focus on near objects decreases over the years, this creates a blurred visual impression that needs to be corrected. This is why farsighted people often hardly notice their farsightedness, if at all, until they reach adulthood.
In farsightedness, the focal point of the eye is mathematically behind the retina, which is why a blurred image is created on the retina. The eye is relatively too short, or the cornea is relatively too flat for the length of the eye.
Refractive surgery can also be used for long-sightedness surgery. Hyperopia is corrected by laser or lens surgery in laser eye centers.
In astigmatism, the curvature of the cornea (sometimes also of the lens) is unevenly greater in one direction than in another. Almost every eye has some degree of astigmatism.
In some people, however, this imbalance is so strong that incoming light rays are focused on several points of the retina. As a result, they have poorer vision both near and far.
Astigmatism can be corrected using
can be corrected.
Presbyopia is the age-related loss of the eye's ability to focus.
At a young age, the lens of the eye is soft and flexible and can easily change its shape so that the eye can focus on objects near and far. From the age of 50 , the lens of the eye loses its elasticity and the eye becomes less and less able to focus on near objects.
Initially, the difficulties begin in dim lighting, but later they are also present in good lighting.
Presbyopia cannot be completely corrected by laser refractive surgery. However, so-called monovision can be achieved. This means that one eye is optimized for near vision and one for distance vision.
If the lack of elasticity of the lens is compounded by a clouding (cataract), it may make sense to insert an artificial lens. To do this, the body's own lens is completely removed. However, these are usually set for a specific distance, whereas multifocal lenses can also be set for several focus ranges.
The cornea is the main contributor to the overall refractive power of the eyes. The strength of the refractive power depends on the curvature of the corneal surface. The steeper the surface, the more strongly the incident light is refracted; the flatter the surface, the less light is refracted.
Myopia and hyperopia in the eye and their correction © bilderzwerg / Fotolia
Laser eye surgery makes use of these physical principles. The surface curvature of the cornea is changed in order to favorably influence the refractive power of the eye.
To do this, the surgeon uses special laser systems to remove fine sections of the cornea according to a precisely calculated pattern. He vaporizes tissue in a fraction of a second. If the curvature is too steep, it is attenuated; if it is not curved enough, the radii of curvature are made steeper.
Structure of the cornea © bilderzwerg / Fotolia
The described tissue ablation can take place in different levels or depth layers of the cornea. Depending on which procedure is used, these layers lie
Laser surgery procedures include
LASIK stands for laser in situ keratomileusis, which means reshaping of the cornea using laser energy.
As extremely fine tissue removal is possible using lasers, the curvature of the cornea can be remodeled.
First, a fine superficial lamella is prepared. A so-called microkeratome can be used for this. This uses a rapidly oscillating blade to separate a lamella at the front of the cornea. The lamella is not cut off completely, but remains connected to the cornea on one side. The lamella, also known as a "flap", is knocked aside so that the inside of the corneal tissue is exposed.
The desired amount of corneal tissue is then vaporized with short flashes of light using an excimer laser. This changes the refractive power and corrects the defective vision. The flap is then folded back into position so that the corneal surface is intact.
The corneal flap can also be prepared using a femtosecond laser system (fs laser or femto-LASIK).
This laser device emits short flashes of infrared light that are focused with the utmost precision at pre-calculated points on the cornea. Each flash leads to a separation point in the corneal layers. Following a computer-controlled pattern, thousands of such light signals are focused into the cornea, ultimately forming a lamella.
Compared to the lamella, which can be cut using a microkeratome, the "femtosecond laser flap" is even more precise. The rest of the procedure is as described for LASIK.
LASEK stands for laser-assisted subepithelial keratomileusis. As with LASIK, this involves reshaping the cornea using laser energy. As with LASIK, an extremely fine removal of tissue is carried out using a laser to remodel the corneal curvature.
LASEK uses a special alcohol-based solution that is applied to the surface of the eye for a few seconds. It loosens the epithelium from its firm anchorage on the corneal surface and exposes the actual corneal substance.
The layer can then be lifted from the surface as a thin flap and pushed aside. As soon as the surface of the corneal tissue is exposed, the desired tissue removal can be carried out by exposing it to short laser pulses.
The laser pulses are computer-controlled. This ensures that exactly as much tissue is removed as is necessary for curvature correction. The epithelial flap is then pushed back over the surface, which acts like a natural bandage.
In addition, a protective contact lens is applied and left in place for a few days to allow the surface to heal.
During the first few days after the operation, the eyes may feel uncomfortable and watery.
Photorefractive keratectomy(PRK) is the predecessor procedure to LASEK.
In this procedure, the epithelium is not detached with alcohol, but the uppermost layer of the cornea is removed directly. The resulting wound closes within a few days as the cell layer grows back. Long-term results are already available for this procedure, as it has been tried and tested since 1984.
Other refractive surgery procedures include
If the cornea is only slightly curved , this can be corrected in certain cases using special relief incisions (fragmentation). These special relief incisions can also be performed as part of cataract surgery to optimize the refractive result.
Some corneal diseases lead to a "bulging" of the cornea (so-called keratoconus). Under certain conditions, it can be useful to stabilize the cornea by inserting tiny struts.
This can at least partially compensate for the reduction in vision caused by the deformation of the cornea.
Not all degrees of short-sightedness or long-sightedness can be treated using laser procedures. For example, if too much corneal tissue is removed with the laser, too little tissue may remain. This can cause the eye to lose its stability.
It can therefore make sense for people with severe short-sightedness or long-sightedness to compensate for the defective vision by implanting an artificial lens. This involves either inserting an additional artificial lens(intraocular contact lens - ICL) into the eye or replacing the patient's own lens with an artificial lens.
If an artificial lens is inserted into the eye in addition to the patient's own lens, this is known as a phakic intraocular lens. This is mainly used for very severe short-sightedness, possibly in conjunction with high astigmatism. It is used less frequently for long-sightedness.
The additional lens can be positioned in the anterior chamber of the eye (between the cornea and iris) or fixed in the iris itself.
Replacing the natural lens of the eye with an artificial lens is usually performed for cataracts.
You can find out whether correcting defective vision using refractive surgery is possible and sensible by talking to your ophthalmologist.
Favorable conditions are:
Every decision to undergo refractive surgery is highly individual. It is based on the wishes and needs of the person affected and the possibilities and recommendations of the ophthalmologist. Some reasons that speak in favor of laser eye surgery are
In refractive surgery, the doctor checks visual acuity using reading tests (reading charts). The patient tries to recognize letters or symbols from a certain distance.
A person with normal vision (visual acuity = 1.0) can recognize objects with a resolution of one angular second. This measurement is subjective.
The ophthalmologist determines which treatment is most promising © peopleimages.com | AdobeStock
Skiascopy is available for the objective measurement of the refractive power of the eye (refraction). This can already be carried out on small children and babies. The unit of measurement for the refractive power of the eye is the diopter.
Refraction can also be measured using an autorefractometer. This is a device that performs projection and focusing using photosensors and image processing.
The doctor can also determine which correction is necessary to compensate for the astigmatism. To do this, he holds toric lenses in front of the eye. These distort the image.
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