Femto-LASIK and LASIK – Modern Techniques in Precision Laser Eye Surgery (Femto LASIK)

Femto-LASIK is a refractive surgery procedure used to correct vision problems. Using Femto-LASIK, doctors can, for example,

• nearsightedness,
• farsightedness, and
• astigmatism

.

Unlike standard LASIK, the Femto-LASIK method does not require a mechanical incision in the cornea. In standard LASIK, the doctor uses a precision mechanical device for this purpose. 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 derived from the initial letters of Laser-Assisted in situ Keratomileusis. This roughly translates to “shaping the cornea in situ using a laser.” “Femto” stands for the femtosecond laser.

Femtosecond laser for refractive surgery; By Philos2000 – Own work, CC BY-SA 3.0, Link

The goal of Femto-LASIK: Sharp vision without glasses

The purpose of the surgery is to enable patients with refractive errors to see well without visual aids. The cause of nearsightedness or farsightedness is the eye’s incorrect refractive power. The cornea, or rather the curvature of the cornea, plays an important role in this. It refracts the light entering the eye. In these refractive errors, the refractive power is too high or too low in relation to the length of the eyeball.

LASIK alters the curvature of the cornea through precisely controlled tissue removal:

• Tissue removal in the center of the cornea flattens the cornea, reduces its refractive power, and thus corrects existing nearsightedness.
• Tissue removal toward the edge of the cornea increases the curvature and refractive power, thereby correcting farsightedness. In cases of astigmatism, LASIK can normalize the irregular curvature of the cornea.

Femto-LASIK Compared to PRK

The LASIK procedure was developed in 1989 as an alternative to photorefractive keratectomy (PRK). Femto-LASIK has been available since 2001.

In PRK, after the wafer-thin corneal epithelium is removed, the laser is used directly on the surface of the cornea. After the surgery, the cornea is essentially an open wound until the corneal epithelium has regrown.

For several days, PRK patients experience quite severe pain due to the exposed nerve endings in the cornea. Because of the increased risk of infection, protective contact lenses must be worn.

The LASIK procedure has successfully eliminated these problems. In this procedure, at the start of the process, not only is the corneal epithelium removed, but a sort of slightly thicker “lid”—known as a flap—is created. The doctor cuts this flap, along with the epithelium, from the upper layers of the cornea.

The flap, which is about one-tenth of a millimeter thick, is repositioned after the laser treatment is complete. In this way, the cornea is protected after the laser treatment as if by a natural bandage. An eye patch is usually no longer necessary as early as the day after the procedure—except while sleeping. Pain is minimal.

Another advantage of this method is that results are achieved much more quickly. Most patients can see clearly again shortly after the surgery. They also notice an immediate improvement in their visual acuity. This makes it possible to treat both eyes simultaneously without any issues.

These advantages have led to LASIK’s rapid adoption. Between 2004 and 2014, the EUREQUO database collected information on more than 27,000 refractive surgery procedures. According to this data, LASIK reached the peak of its popularity in Europe in 2007, accounting for 85 percent of all “glasses-free” surgeries.

From then on, however, both the absolute numbers and the relative share declined again to 40 percent in 2014. Since then, photorefractive keratectomy has been experiencing a renaissance.

If you have your previous eyeglass prescriptions or an eyeglass/contact lens prescription card, please bring them with you to the examination. This also applies to any medical reports from your ophthalmologist. On the day of the preoperative examination and on the day of surgery, you should also avoid wearing eye makeup.

The preoperative examination for Femto-LASIK usually takes two to three hours and includes a series of measurements. Before the Femto-LASIK procedure, the doctor measures the eye’s refractive error as well as the corneal thickness and corneal profile.

A computer program calculates the amount of tissue that needs to be removed at each point on the corneal surface to achieve the desired curvature. During the surgery, this data controls the movement and operation of the computer-controlled laser device.

You should not wear contact lenses for two weeks prior to Femto-LASIK: The measurements are precise to one-hundredth of a millimeter, 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. For this reason, you must not drive afterward. Your companion may be present during the measurements and consultation.

Refractive surgery, including Femto-LASIK, corrects vision defects © reineg / Fotolia

Immediately before the brief procedure, the eye is anesthetized and an eyelid retractor is applied to keep the eyelids open.

The procedure is entirely computer-controlled. The surgeon monitors the progress of the procedure through a surgical microscope, whose image is transmitted to a monitor. In the first step of the surgery, the flap is cut using the femtosecond laser.

The femtosecond laser is an infrared laser. It perforates the cornea with extremely short energy pulses so that the outermost layer can be folded aside like a lid (flap).

The rest of the procedure proceeds as in PRK: The exposed inner surface of the cornea is precisely reshaped using the UV light pulses of an excimer laser at thousands of closely spaced points. Eye-tracking feedback ensures that the laser moves in sync with eye movements.

This central step of the surgery is completed in less than a minute. The cornea is rinsed, dried, and covered with the flap.

In most cases, the eye socket is protected with a transparent bandage immediately after the procedure. From start to finish, the Femto-LASIK procedure takes about a quarter of an hour per eye. As early as the next day, patients usually have good vision and get a first impression of their improved visual acuity.

Antibiotic and lubricating eye drops are used for the first week after Femto-LASIK surgery. The lubricating, moisturizing drops are recommended for 4 to 6 weeks after the procedure; eye gels or ointments may also be used as needed.

Quite good visual acuity is often achieved within one to two days, and stable visual acuity is typically reached within a month.

Most patients experience only a slight sensation of a foreign body in the eyes during the first few days after Femto-LASIK. Increased glare and reduced night vision are commonly observed in the first few weeks. These symptoms may occur particularly in patients with very large pupils and higher correction values.

The first follow-up appointment takes place the following day at the clinic. After about one week, you will come in for a follow-up examination, and the final examination takes place after two to three months. Of course, your ophthalmologist can also perform these follow-up examinations.

However, LASIK and Femto-LASIK also have disadvantages compared to PRK. Healing after PRK may be slow, but it does eventually complete.

The main drawback of LASIK is flap-related complications. The inner corneal tissue cannot truly regenerate (otherwise laser eye surgery would not work at all). As a result, the area where the cornea was cut remains slightly unstable in the long term.

Germs can enter the interior of the cornea through the incision. The corneal epithelium can grow into the lower layers of the cornea and cloud the normally crystal-clear tissue. In addition, there are frequent cases in which the LASIK flap suddenly detaches again, even years after the surgery.

Furthermore, severing the corneal nerves while cutting the flap carries a certain risk of damage: The cornea often loses its ability to sense its own moisture levels for an extended period—and in some cases, permanently. As a result, the signals to the lacrimal gland to produce tears are lost.

The result is dry eyes, a condition that many patients can manage with eye drops. In rare cases, however, dry eyes can develop into a serious condition: it threatens vision and causes chronic pain.

In the week following the procedure, you may experience

• mild to moderate pain,
• burning and watery eyes,
• a sensation of a foreign body,
• blurred vision, and
• sensitivity to light

may occur. Dry eyes and problems with night vision (sensitivity to glare, halos around light sources) are normal during the first and second months after surgery. However, they sometimes persist longer. The night vision problems are related to scarring along the edges of the flap.

Visual acuity stabilizes in the weeks following the procedure. During this time, fluctuations in visual acuity are still to be expected.

• Ultimately, about 95 percent of LASIK patients have significantly better visual acuity after the procedure than they did before.
• However, about 15 percent do not achieve complete freedom from glasses. They still require visual aids, at least for demanding visual tasks.
• Flap complications (see above) are expected in about 0.4 percent of patients.

The most serious complication of laser eye surgery is keratectasia. This is a destabilization of the corneal tissue that leads to increasing deformation of the corneal surface. At the same time, visual acuity deteriorates.

Keratectasia occurs in 0.04 to 0.6 percent of laser eye surgery patients—sometimes not until 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, or a foreign body sensation due to dry eyes,
• impaired coordination between both eyes.

Starting at age 40, you may need reading glasses for close-up vision. You should wear them when necessary.

Possible complications with Femto-LASIK

• Overcorrection or undercorrection, requiring further surgery or corrective lenses.
• Loss of vision: It cannot be ruled out with absolute certainty that LASIK—for example, due to an infection that cannot be controlled with medication—could result in loss of vision.
• Increased sensitivity to light and glare—possibly permanent.
• Reduced night vision—possibly permanent.

In addition, late complications may occur. PRK and LASIK are “relatively” new treatment methods. It cannot be ruled out with absolute certainty that complications may arise in later years. For example, the cornea could become weakened (keratectasia), which is associated with a significant deterioration in vision.

Even in cases without complications, surgical correction of refractive errors involves inherent problems. For example, the flattening or steepening of the cornea required for the respective correction may lead to a deterioration in the cornea’s optical imaging qualities.

This also means a reduction in best-corrected visual acuity compared to the condition prior to Femto-LASIK surgery. This is even more pronounced if there are delays in the healing of the corneal flap, or if wrinkles or scarring occur.

Under certain anatomical conditions of the eye, difficulties may arise during the preparation of the corneal flap. This risk is particularly present with microkeratome LASIK. This can lead to an interruption or rescheduling of the procedure, or may make another method seem advisable. By using the femtosecond laser in Femto-LASIK, this complication can be virtually eliminated!

Femto-LASIK is generally suitable for people with

• myopia (nearsightedness) up to approximately -9 diopters
• hyperopia (farsightedness) up to approximately +4 diopters
• astigmatism (corneal curvature) up to +/- 3 diopters

. Additional requirements include

• stable (non-progressive) vision correction,
• corneal thickness of at least 480 micrometers,
• no systemic diseases such as rheumatism or diabetes,
• no inflammatory or degenerative corneal diseases, in particular no “dormant” keratoconus (progressive thinning and bulging of the cornea).

In general, Femto-LASIK is a proven, well-researched, and relatively safe method for the permanent correction of mild to moderate refractive errors in suitable patients.

Femto-LASIK is now considered one of the most precise methods in laser eye surgery and offers significant advantages over conventional LASIK. Through the use of modern femto-technology, the corneal flap can be created with exceptional precision without using a mechanical microkeratome. While conventional LASIK or microkeratome-based LASIK still relies on a so-called microkeratome, the preparation in Femto-LASIK is performed entirely with a special laser. This results in uniform flaps and a very thin corneal flap, which enhances safety. The combination of an excimer laser and a femtosecond laser enables effective correction of refractive errors using the excimer laser. Femto-LASIK treatment yields particularly good results for astigmatism as well as nearsightedness and farsightedness.

When comparing Femto-LASIK and LASIK, many patients choose the Femto-LASIK method because of its advantages. The LASIK procedure itself usually takes about 10 minutes per eye and is performed using eye drops, making the procedure comfortable for the patient. Economic factors, such as the cost of Femto-LASIK—which often ranges in the range of several € per eye—also play a role in the decision. Alternative procedures such as ReLEx SMILE or Smile Pro also offer modern options within refractive surgery. Nevertheless, Femto-LASIK remains an established standard in laser in situ keratomileusis.

Studies, such as those published in the *Journal of Cataract and Refractive Surgery* or in *Refractive Surgery 2015*, confirm the high precision and safety of this method. Companies such as Carl Zeiss Meditec AG have played a key role in driving technological development forward. Overall, it is clear that LASIK and Femto-LASIK are leading the field of refractive surgery. Femto-LASIK offers a reliable solution for laser eye surgery and stands out for its modern technology, high precision, and long-term stable results.

What is Femto-LASIK?
Femto-LASIK is a modern variation of LASIK in which a femtosecond laser is used to create the flap. This makes the procedure particularly precise and safe.

How does Femto-LASIK differ from conventional LASIK?
In conventional LASIK, the flap is created using a microkeratome, whereas Femto-LASIK uses a laser. This reduces the risk of complications and increases precision.

Who is a good candidate for Femto-LASIK?
Femto-LASIK is suitable for patients with nearsightedness, farsightedness, or astigmatism. A prerequisite is sufficient corneal thickness and stable visual acuity.

Is the procedure painless?
Yes, Femto-LASIK is considered painless because the eye is numbed with eye drops during the procedure. After the procedure, you may experience a slight sensation of a foreign body in the eye.

What alternatives are there to Femto-LASIK?
Alternatives include procedures such as SMILE or ReLEx SMILE, which are also used in laser eye surgery. Other methods of refractive surgery are also available.