As early as around the year 1000, an Arab scholar came up with the idea of supporting the eye by means of optical lenses. Around 1240, monks put this idea into practice – the birth of eyeglasses. For centuries, they were the only way to correct defective vision. But in recent years, they have had competition.
Glasses and contact lenses
Eyeglasses and plastic contact lenses can be used to compensate for abnormalities in the refractive power of the eyes – nearsightedness, farsightedness and astigmatism caused by a curvature of the cornea. Similar to a prosthesis on an arm or leg, these aids allow more or less normal function – but only for the duration of wear.
Refractive surgery: pros and cons.
For several years, there has also been the possibility of permanently correcting defective vision by means of various surgical procedures. This subfield of ophthalmology is called “refractive surgery”. The advantage of no longer needing troublesome aids after the operation is also countered by disadvantages and risks. A thorough examination, good consultation and careful consideration of all points are therefore indispensable before deciding on an operation. However, refractive surgery procedures have increased massively in recent years – laser treatments on the eye have now been performed around 50 million times worldwide, making them one of the most common operations ever. This means that experience is also more numerous and methods and instruments more sophisticated, making individual risk assessment easier and procedures safer overall.
Surgical procedures at a glance
In principle, laser procedures on the cornea and implantations on the lens can be performed to restore normal vision. Which procedure is used depends on the type and severity of the refractive error. In the case of minor impairments, laser therapies are performed on the cornea; in the case of more severe refractive errors, operations on the lens are an option, possibly in combination with laser therapy of the cornea. Laser surgery on the cornea: The following is a listing of the laser procedures of the cornea that are most commonly used.
- LASIK (laser in situ keratimileusis): this procedure has been in use since 1994 and is the most commonly used. It involves lifting off a thin corneal flap – by microkeratome or now often by femto-second laser. Individual areas on the underlying corneal surface are vaporized using an excimer laser to correct myopia. Subsequently, the corneal flap is put back in its original place. It grows back on its own.
- PRK (photoablative refractive keratectomy): this is the oldest procedure in which the cornea is ablated with an excimer laser. Because the top layer of the cornea is mechanically removed in this procedure, the surface wound is larger than in LASIK. Therefore, the procedure is usually more painful and healing takes a little longer. Advantage: If complications occurind they are less severe than with LASIK.
- LASEK and Epi-LASIK are special forms of PRK, in which the upper corneal layer is lifted off differently. They combine the advantages of PRK (easier complications) and LASEK (fast healing).
Currently, there are four ways in which the cornea is measured and treated to tailor the refractive error (wavefront-optimized, wavefront-guided, topography-guided, Q-value-optimized). Lens surgery: Refractive lens surgery has also been used for years. This form of procedure is used when there are reasons against the corneal laser procedure. This is especially true in cases of higher degree refractive error (from -10 diopters in myopia and +4 diopters in hyperopia).
- Phakic lens: This is a type of contact lens that is implanted in the eye in addition to the patient’s own lens. This procedure is used mainly in young people: in the anterior chamber of the eye, that is, between the cornea and iris (Artisan lens) or in the posterior chamber of the eye, that is, between the iris and the body’s own lens (implantable contact lens = ICL).
- Clear Lens Exchange: in older people (from 45) or very severe myopia (> -20 diopters), the own lens is replaced by the artificial lens. This has the disadvantage that the eye thereby loses its ability to adjust to different distances (accommodation).
Which procedure when?
Here is an overview of when which procedure is usually used – however, these are only guidelines, which are reviewed in individual cases and modified if necessary. Nearsightedness (myopia)
- Low, stable myopia (up to -3 diopters) and lack of corneal curvature: corneal implant (Intrastromal Corneal Ring = ICR), a very thin arc-shaped plastic part that is inserted at the edge of the cornea (and can be changed).
- Moderate myopia: LASIK up to -10 diopters, PRK up to -6 diopters.
- Stronger myopia (-10 to -20 diopters): phakic lens.
- Severe myopia (from -20 diopters): complete lens replacement (Clear Lens Exchange).
Farsightedness (hyperopia)
- Low farsightedness (up to +4 diopters): LASIK.
- Medium hyperopia: phakic lens.
- Tärkere hyperopia (from +8 diopters): complete lens replacement.
Corneal curvature (astigmatism).
- Minor corneal astigmatism (up to 3 (5) diopters): LASIK, PRK
- Stronger form (from 3 diopters): astigmatic keratotomy (AK), in which the curvature is reduced by small arcuate incisions; also complete lens replacement possible.
Who is eligible?
In principle, some requirements must be met so that the affected person is eligible for one of these operations at all: the vision must not have changed in the months before, the patient should be 18 years old. Other eye diseases, certain general diseases, for example of the immune system, medications or allergies can speak against an operation. The results of the operation depend on the extent and type of refractive error. They are better the smaller the refractive error, better for nearsightedness than for farsightedness, and corneal curvature affects success.
What is the procedure?
Many specialized clinics offer information evenings, after which you can make an individual appointment with detailed consultation and initial examinations. This will determine whether any of the procedures are suitable at all, and if so, which one. This is followed by detailed preliminary examinations of the eyes. As a rule, one eye is operated on first and waited until its vision has returned to normal. In some cases (especially so-called monovision in presbyopia), the result of the operation is simulated beforehand with contact lenses to check whether it is individually tolerable. Several control examinations are important to evaluate the healing process. It is also important that the patient strictly adheres to the prescribed therapy guidelines. The costs are usually not covered by the statutory health insurance. For the actual operation, one can estimate 1200 to 2500 euros per eye; this includes the costs for pre- and postoperative examinations and any fine correction that may be necessary within twelve months after the operation.
What are the risks of refractive surgery?
Like any surgical procedure, these procedures carry risks – though experts disagree about their likelihood. Infections, image distortion and increased sensitivity to glare can occur. Overcorrections, undercorrections and incorrect corrections also occur, and not all of them can be corrected by a second operation. Twilight and night vision, in particular, are often impaired. The risk of blindness is considered to be very low. It is very important to consider one’s own motivation, to critically examine the methods and to seek advice from independent specialists – if necessary from several. By the way: It is very likely that even if the operation is successful, glasses will have to be worn from about 45 to 50 years of age due to presbyopia. It is also up to you to decide whether you want to take the risk of an eye operation abroad. These operations are usually a lot cheaper, but they involve travel costs and possible imponderables and risks. On the Internet you can find some forums where the topic of “LASIK tourism” is discussed.
