Femto-LASIK is a refractive surgery procedure that can be used to correct defective vision. Using Femto-LASIK, doctors can correct, for example
corneal curvature.
In contrast to standard LASIK, the Femto-LASIK method does not require a mechanical incision in the cornea. With standard LASIK, the doctor uses a mechanical precision device. With Femto-LASIK, a femtosecond laser is used to cut the corneal flap. Femto-LASIK is therefore very gentle on the cornea.
The abbreviation LASIK is formed from the first letters of Laser-Assisted insitu Keratomileusis. This means something like "shaping the cornea in situ using a laser". Femto stands for femtosecond laser.
Femtosecond laser for refractive surgery; By Philos2000 - Own work, CC BY-SA 3.0, Link
The aim of femto LASIK: sharp vision without glasses
The purpose of the operation is to enable patients with defective vision to see well without visual aids.
The cause of short-sightedness or long-sightedness is the incorrect refractive power of the eye. The cornea, or the corneal curvature, plays an important role in this. It refracts the light falling into the eye. The refractive power is too high/low in relation to the length of the eyeball.
LASIK changes the corneal curvature by precisely dosed tissue removal:
- Tissue removal in the center of the cornea flattens the cornea, reducing its refractive power and thus any existing myopia.
- Tissue removal towards the edge of the cornea increases the curvature and refractive power and counteracts long-sightedness. In the case of astigmatism, LASIK can normalize the irregular curvature of the cornea.
Femto-LASIK in comparison with PRK
The LASIK procedure was developed in 1989 as an alternative to photorefractive keratectomy (PRK). Femto-LASIK has been available since 2001.
In PRK, the laser is used to work directly on the surface of the cornea after removing the wafer-thin corneal epithelium. After the operation, the cornea is virtually an open wound until the corneal epithelium has grown back.
For a few days, PRK patients experience quite severe pain due to the exposed nerve endings in the cornea. Due to the increased risk of infection, bandage contact lenses must be worn.
The LASIK procedure has successfully avoided these problems. At the beginning of the procedure, not only is the corneal epithelium removed, but a kind of slightly thicker "lid" is created: The so-called flap. The doctor cuts this flap together with the epithelium from the upper layers of the cornea.
The flap, which is around a tenth of a millimeter thick, is replaced after the laser treatment is complete. In this way, the cornea is protected after laser treatment as if by a natural wound dressing. An eye bandage is usually no longer necessary the day after the procedure, except when sleeping. There is hardly any pain.
Another advantage of the method: success is achieved much more quickly. Most patients can see again without any problems shortly after the operation. They also notice the improvement in their visual acuity immediately. This means that both eyes can easily be treated at the same time.
These advantages have led to LASIK quickly gaining acceptance. The EUREQUO database collected information on more than 27,000 refractory surgical procedures between 2004 and 2014. According to this data, LASIK reached the peak of its popularity in Europe in 2007 with an 85 percent share of all spectacle-removal surgeries.
From then on, however, both absolute values and relative share fell again to 40 percent in 2014. Since then, photorefractive keratectomy has experienced a renaissance.
If you have previous spectacle values or a spectacle/contact lens passport, please bring these with you to the examination. This also applies to reports from your ophthalmologist. You should also not wear eye make-up on the day of the pre-examination and on the day of the operation.
The pre-examination before Femto-LASIK usually takes two to three hours and includes a series of measurements. The doctor measures the refractive error of the eye as well as the corneal thickness and the corneal profile before the Femto-LASIK treatment.
A computer program calculates the amount of tissue removal required to create the desired curvature for each point on the corneal surface. This data controls the movement and activity of the computer-controlled laser device during the operation.
You should not wear contact lenses for two weeks before Femto-LASIK: every hundredth of a millimeter is important for the measurements and wearing contact lenses distorts the measurement results.
A detailed consultation will take place after the examination.
Due to pupil dilation, you will not be able to see clearly for the rest of the day after the examination. You are therefore no longer allowed to drive. Your companion can be present during the measurements and consultation.
Refractive surgery, including Femto-LASIK, corrects visual defects of the eye © reineg / Fotolia
Immediately before the short procedure, the eye is anesthetized and an eyelid retractor is placed to keep the eyelids open.
The procedure is completely computer-controlled. The surgeon monitors the progress of the procedure using a surgical microscope, the image of which is transmitted to a monitor. In the first step of the operation, the flap is cut with the femtosecond laser.
The femtosecond laser is an infrared laser. It perforates the cornea with extremely short energy pulses so that the uppermost layer can be folded aside like a flap.
The rest of the procedure is similar to PRK: the exposed corneal interior is precisely remodeled with the UV light pulses of an excimer laser at thousands of closely adjacent points. Eye tracking feedback ensures that the laser moves with the eye movements.
This central step of the operation is completed after barely a minute. The cornea is rinsed, dried and covered with the flap.
The eye socket is usually protected with a transparent bandage immediately after the operation. From start to finish, the Femto-LASIK treatment takes about a quarter of an hour per eye. Patients usually have good vision and a first impression of their improved vision the very next day.
Antibiotic and wetting eye drops are used for the first week after Femto LASIK surgery. The wetting, nourishing drops are recommended 4 to 6 weeks after the procedure, as well as eye gels or ointments if required.
Good visual acuity is often achieved after one to two days and stable visual acuity within a month.
Most patients only notice a slight foreign body sensation in the first few days after Femto-LASIK. Increased glare and reduced night vision are often observed in the first few weeks. They can occur particularly in patients with very large pupils and higher corrections.
The first follow-up check takes place the following day in the clinic. After approximately one week, you will come for a follow-up examination, and the final examination will take place after two to three months. Your ophthalmologist can of course also carry out the follow-up examinations.
LASIK and Femto-LASIK also have disadvantages compared to PRK. Healing after PRK may be slow, but it is actually completed at some point.
The weak point of LASIK is the flap complications. The inner corneal tissue cannot really regenerate (otherwise laser eye surgery would not work at all). For this reason, the area where the cornea was cut always remains somewhat unstable in the long term.
Germs can penetrate into the cornea through the incision. The corneal epithelium can grow into the lower layers of the cornea and cloud the crystal-clear tissue. In addition, there are always cases in which the LASIK flap suddenly comes loose again years after the operation.
Furthermore, the severing of the corneal nerves when cutting the flap harbors a certain potential for damage: the cornea often lacks the sensitivity to measure its moistening state for a long time, in some cases even permanently. As a result, the signals to the lacrimal gland to produce tear fluid are missing.
The result is dry eyes, a condition that can be kept in check with eye drops for many sufferers. In rare cases, however, dry eyes can also develop into a serious illness, threatening vision and causing chronic pain.
In the week following the procedure, you may experience
- Mild to moderate pain,
- burning and watery eyes,
- a foreign body sensation,
- blurred vision and
- sensitivity to light
may occur. Dry eyes and problems with night vision (sensitivity to glare, halos around light sources) are normal in the first and second month after the operation. However, they sometimes last longer. Night vision problems are related to scarring at the edges of the flap.
The optical result stabilizes in the weeks following the operation. During this time, fluctuations in visual acuity can still be expected.
- Ultimately, around 95 percent of LASIK patients have significantly better visual acuity after the procedure than before.
- However, around 15 percent do not achieve complete freedom from glasses. They still need a visual aid, at least for demanding visual tasks.
- Flap complications (see above) are to be expected in around 0.4 percent of patients.
The most dramatic complication of laser eye surgery is corneal ectasia. This is a destabilization of the corneal tissue, which leads to an increasing deformation of the corneal surface. At the same time, visual acuity deteriorates.
Corneal ectasia occurs in 0.04 to 0.6 percent of laser eye surgery patients - sometimes years after the procedure.
Possible temporary side effects during the healing process after Femto-LASIK
- Increased sensitivity to light and glare, possibly permanent,
- Temporary overcorrection,
- Burning, itching, foreign body sensation due to dry eyes,
- disturbed cooperation of both eyes.
From the age of 40, reading glasses for close-up vision may be necessary. You should then also wear these.
Possible complications with Femto-LASIK
- Over- or undercorrection with the need for further surgery or corrective lenses.
- Loss of vision: It cannot be ruled out with absolute certainty that LASIK may result in loss of vision, e.g. due to an infection that cannot be controlled with medication.
- Increased sensitivity to light and glare - possibly permanently.
- Reduced night vision - possibly permanent.
Late complications may also occur. PRK/ LASIK are "relatively" new treatment methods. It cannot be ruled out with absolute certainty that complications may occur in later years. For example, the cornea could be weakened (keratectasia), which is associated with a significant deterioration in vision.
Even if there are no complications, there are fundamental problems with the surgical correction of defective vision. For example, the flattening or splitting of the cornea required for the respective correction may lead to a deterioration in the optical imaging quality of the cornea.
This also means a reduction in the best-corrected visual acuity compared to the state before the Femto-LASIK operation. This is all the more the case if there is a delay in healing of the corneal flap, wrinkling or scarring.
Under certain anatomical conditions of the eye, there may be difficulties in preparing the corneal flap. This risk is particularly present with microkeratome LASIK. This can lead to an interruption or rescheduling of the procedure or make another method appear advisable. By using the femtosecond laser in Femto-LASIK, this complication can be almost completely ruled out!
Femto-LASIK is generally suitable for people with defective vision with
- Myopia (short-sightedness) up to approx. -9 diopters
- Hyperopia (long-sightedness) up to approx. +4 diopters
- Astigmatism (curvature of the cornea) up to +/- 3 diopters
suitable. Further requirements are
- Stable (non-progressive) defective vision,
- corneal thickness not less than 480 micrometers,
- No systemic diseases such as rheumatism or diabetes,
- No inflammatory or degenerative corneal diseases, in particular no "dormant" keratoconus (progressive thinning and protrusion of the cornea).
In principle, Femto-LASIK is a proven, well-researched and relatively safe method for the permanent correction of mild to moderate visual defects for suitable patients.
LASIK has been used for over 20 years as the most advanced and most commonly used procedure for correcting vision defects. The combination of microsurgical incision technique and tissue vaporization using the excimer laser achieves particularly fast and precise results. The advantages are
- Large correction area,
- rapid regeneration of visual acuity,
- pain-free healing phase,
- stable results.