The designation Refractive surgery serves as a collective term for eye operations in which the total refractive power of the eye is changed. This way, the patient no longer needs glasses or contact lenses.
What is Refractive Surgery?
Refractive surgery is understood to mean all surgical interventions on the eye that lead to a change in the overall refractive power of the eye. With these procedures, it is possible to replace conventional visual aids such as glasses or contact lenses. Refractive surgery is considered effective and safe for correcting visual defects.
Refractive surgery began in the early 20th century. In the 1930s, the first corneal modeling studies were undertaken, including experiments on radial keratomy to correct myopia. At the time, however, these procedures often had complications such as scarring the cornea. From 1978 onwards, radial keratomy was increasingly used in the USA and the USSR. In 1983, refractive correction using an excimer laser was described for the first time. The first treatment on humans took place in 1987 in Berlin with photorefractive keratomy (PRK).
In the following years, this method was further developed into the LASEK procedure. From 1989 keratomileusis could be combined with the excimer laser method. The new procedure was named LASIK (laser in situ keratomileusis).
In Germany around 0.2 percent of all German citizens were treated using refractive surgery procedures. Approximately 25,000 to 124,000 interventions take place every year. The tendency is increasing.
Function, effect & goals
Refractive surgery is used to correct ametropia such as nearsightedness, farsightedness and asthma. An axial refractive visual defect is present when the length of the eyeball and the focal length of the optics system do not match. Short-sightedness (myopia) is when the eyeball is too long to refractive power.
On the other hand, if the eyeball is too short, farsightedness (hyperopia) occurs. If there are different focal points in different meridians in the optics system of the eye, it is a question of astigmatism (corneal curvature). With the help of the methods of refractive surgery, the total refractive power of the optical system can be adjusted in such a way that the surroundings appear sharp on the retina. Either the refractive power of the cornea is changed or the eye lens is replaced or supplemented by implantation. The refractive power is corrected by changing its curvature.
For this purpose, the ophthalmologist removes tissue with a laser or makes defined incisions. The intraocular pressure leads to a changed shape. While nearsightedness reduces the refractive power, farsightedness increases the refractive power. However, presbyopia cannot be corrected with the help of refractive surgery. A therapeutic restoration of this ametropia is not possible.
Nowadays it is primarily laser procedures for the application of refractive surgery that have prevailed. The most common method is the LASIK procedure. With the help of a fine femtosecond laser or a microkeratome, the ophthalmologist cuts a lamella with a diameter of 8 to 9.5 millimeters into the cornea of the eye. Then he folds the epithelium aside and treats the ametropia with the help of laser technology. As a rule, only 30 seconds are required for each laser irradiation, but this ultimately depends on the extent of the ametropia.
The LASIK method has the advantage that patients have full vision again a few hours after the procedure. This means that the cornea does not have to grow back because it is simply pushed aside during the operation. In addition, the patient feels almost no pain. The LASIK procedure is used for small to medium corrections. The visual defect range fluctuates between +4 and -10 diopters.
Another method of refractive surgery is the LASEK procedure. During this procedure, tissue is removed from the skin. With the help of alcohol, the ophthalmologist completely removes the epithelium. After the procedure, the patient is given a wound dressing that protects the cornea. The EpiLASEK process is a variant of the LASEK method. In this method, the epithelium is lifted off with a microkeratome.
The oldest laser procedure in refractive surgery is photorefractive keratomy. During this procedure, the ophthalmologist removes the epithelium with a special plane. Then it has to form anew. It takes a certain amount of time before the eyesight is restored. Refractive surgery also includes the insertion of intraocular lenses, which are artificial lenses made from different materials that are biocompatible. They are implanted in the eye, thereby changing its overall refractive power.
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As with all other surgical procedures, there is also the possibility of risks and side effects with refractive surgery. For this reason, a detailed consultation with the ophthalmologist should always take place before deciding on this type of procedure.
One of the most common complications of refractive eye surgery is impaired vision. This can u. a. noticeable through a restricted view at dusk or in the dark. Other possible side effects are a gloss effect, the development of halos or halogens, and a reduced contrast sensitivity. Occasionally the patient perceives phenomena in the field of vision. Over or under corrections are also conceivable after the procedure. They arise by changing the diopters again.
In most cases, follow-up treatment is needed to correct the complications. Another intervention can be helpful. Some patients also experience rare side effects such as eye irritation, redness, or severe tearing.
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