The term refractive surgery serves as a collective term for eye surgeries in which the overall refractive power of the eye is changed. In this way, the patient no longer needs glasses or contact lenses.
What is refractive surgery?
The term refractive surgery serves as a collective term for eye surgeries that alter the overall refractive power of the eye. Refractive surgery refers to all surgical procedures on the eye that result in altering 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 the correction of ocular refractive errors. Refractive surgery had its beginning in the early 20th century. In the 1930s, the first corneal modeling studies were undertaken, which included experiments in radial keratotomy to correct myopia. However, at the time, these procedures not infrequently had complications, such as corneal scarring. Beginning in 1978, radial keratomy was increasingly used in the United States and the USSR. In 1983, refractive correction using an excimer laser was described for the first time. The first treatment in 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 given the name LASIK (laser in situ keratomileusis). In Germany, about 0.2 percent of all German citizens were treated by refractive surgery procedures. Each year, approximately 25,000 to 124,000 procedures are performed. Thereby, the trend is increasing.
Function, effect, and goals
Refractive surgery is used to correct refractive errors such as nearsightedness, farsightedness and astigmatism. An axial refractive error of vision occurs when the eyeball length and the focal length of the optical system do not match. Nearsightedness (myopia) is when the eyeball is too long in relation to the refractive power of the eye. In contrast, farsightedness (hyperopia) occurs when the eyeball is too short. If there are different focal points in the optical system of the eye in different meridians, it is astigmatism (astigmatism of the cornea). With the help of refractive surgery methods, the total refractive power of the optical system can be adjusted in such a way that the environment on the retina appears sharp. 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 causes a change in the shape of the eye. While a reduction of the refractive power is achieved in the case of nearsightedness, an increase of the refractive power is achieved in the case of farsightedness. However, presbyopia cannot be corrected with the help of refractive surgery. Thus, therapeutic restoration of this defective vision is not possible. Nowadays, laser procedures have become the most popular method of refractive surgery. The most common method is LASIK. Using a fine femtosecond laser or a microkeratome, the ophthalmologist cuts a flap with a diameter of 8 to 9.5 millimeters into the cornea of the eye. He then folds the epithelium aside and uses laser technology to treat the refractive error. As a rule, only 30 seconds are needed for each laser irradiation, but this ultimately depends on the extent of the defective vision. The LASIK method has the advantage that patients regain full vision just a few hours after the procedure. Thus, the cornea does not have to grow back because it is merely 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 varies between +4 and -10 diopters. Another method of refractive surgery is the LASEK procedure. In this procedure, tissue is removed from the skin. With the help of alcohol, the ophthalmologist completely detaches the epithelium. After the procedure, the patient receives a wound dressing that protects the cornea. A variant of the LASEK method is the EpiLASEK procedure.In this method, the epithelium is lifted off with a microkeratome. The oldest laser procedure in refractive surgery is photorefractive keratome. In this procedure, the ophthalmologist removes the epithelium with a special plane. Afterwards, it has to form anew. It takes a certain amount of time until the visual acuity is restored. Refractive surgery also includes the insertion of intraocular lenses, which are artificial lenses made of different materials that are biocompatible. They are implanted into the eye, changing its overall refractive power.
Risks, side effects and dangers
As with all other surgical procedures, there is a possibility of risks and side effects with refractive surgery. For this reason, a detailed consultation with an ophthalmologist should always take place before deciding to undergo this type of surgery. One of the most common complications of refractive eye surgery is impaired vision. This can be manifested, among other things, by limited vision at dusk or during the hours of darkness. Other side effects include a glossy effect, the appearance of halos or halogens, and reduced contrast sensitivity. Occasionally, the patient will notice phenomena in the field of vision. Over- or under-corrections are also conceivable after the procedure. These occur when the diopters are changed again. In most cases, follow-up treatment is required to correct the complications. A repeat surgery may be helpful in this process. Some patients also suffer from rare side effects such as eye irritation, redness, or severe tearing.
