KLEx

KLEx stands for Keratorefraktive Lentikel-Extraktion. This is the latest laser eye surgery procedure used to correct vision problems (e.g., nearsightedness and astigmatism). The method is minimally invasive and eliminates the need for glasses and contact lenses.

This procedure is also known under the brand name ReLEx SMILE (Small Incision Lenticule Extraction), SILK, CLEAR or SmartSight and is considered one of the gentlest technologies in laser eye surgery.

Unlike the LASIK method, KLEx involves removing a small disc-shaped piece of tissue (known as a lenticule) from within the cornea using a special laser.

Removing this lenticule changes the curvature of the cornea in such a way that the existing vision defect is corrected.

In the KLEx procedure, the cornea is not opened or removed with a flap, but only a tiny incision of a few millimeters is made: this makes the procedure less invasive.

Since only a tiny opening is required on the side, the stability of the cornea is largely preserved. This makes aftercare easier, as you don't have to be careful not to rub your eyes.

The small opening usually allows the eye to recover more quickly, with fewer postoperative complaints, less dry eyes, and less sensitivity to light in the first few days.

Thanks to state-of-the-art femtosecond lasers, the cornea is corrected without heat or mechanical stress, achieving highly precise results.

KLEx is particularly suitable for short-sightedness and astigmatism.

The KLEx eye laser procedure is minimally invasive and requires only a femtosecond laser. This high-precision laser can make micrometer-precise incisions, meaning that, like all our procedures, it does not require a scalpel.

A femtosecond laser first forms a lenticle inside the cornea, a tiny lens-shaped disc of corneal tissue whose shape corresponds exactly to the visual defect to be corrected. At the same time, the laser creates an access incision on the surface of the cornea that is only about 2 to 4 mm in size. Through this microscopic incision, the surgeon can gently remove the previously detached lenticule. Once the lenticule is removed, the shape of the cornea changes according to the desired vision correction. In the case of nearsightedness, for example, the cornea is flattened slightly so that incoming light rays are focused correctly again. The tiny incision at the edge of the cornea heals quickly on its own, so no sutures are required.

In this way, the visual impairment is precisely corrected without having to create a corneal flap and without removing large areas of the surface.

The advantages of KLEx at a glance:

Only a small 2–4 mm incision:
No large incision, no large wound.

Less dry eyes:
Since only a very small incision is made and the nerve pathways of the cornea remain largely intact, the risk of dry eyes after laser eye surgery is lower than with Femto-LASIK.

High comfort during the procedure:
Since the entire procedure is performed with only one laser, the procedure takes only a few minutes per eye, and anesthetic eye drops make the procedure painless.

In summary, the KLEx procedure is minimally invasive and a particularly gentle laser eye surgery method. It offers precise results thanks to state-of-the-art femtosecond laser technology, fast healing, high treatment comfort, and is also suitable for patients with astigmatism, while at the same time posing a low risk of typical complications associated with older procedures.

up to -8 diopters

not recommended

-5 diopters

KLEx can be used to treat myopia (nearsightedness) and astigmatism (corneal curvature).

Hyperopia (farsightedness) cannot currently be treated with KLEx. There are already laser systems that are being tested for the treatment of hyperopia, but they have not yet been approved.

KLEx is suitable for myopia up to approximately -8 diopters and astigmatism up to approximately -5 dpt.

Patients with astigmatism also benefit from KLEx, as the laser not only compensates for nearsightedness, but also corrects existing corneal curvature in the same step.

Actual suitability depends on your individual corneal thickness and eye condition. During the brief examination, we will work with you to determine which procedure is best for you. The brief examination at YOUSEE is free* and non-binding.

* Free consultation by our trained, non-medical staff.

The KLEx procedure is the most recent of the three most commonly used laser eye surgery procedures worldwide. In this video, our ophthalmologist Prof. Theo G. Seiler, MD, FEBO Ophthalmologist FMH introduces KLEx, which is often referred to online by its brand name, ReLEx SMILE.

The KLEX laser eye surgery procedure is considered one of the safest, most modern, and best researched laser eye surgery procedures. Serious complications are extremely rare, and studies confirm the high effectiveness and safety of the method.

Important: A detailed personal consultation with us and a thorough preliminary examination are essential for the success of the operation.

Your health is always our top priority: Our internal guidelines are stricter than the international standard.

Summary: KLEx is an effective and reliable solution for permanently eliminating the need for glasses and contact lenses.

* Free consultation with our trained, non-medical specialists.

Adults who suffer from refractive errors and wish to have their vision permanently corrected are generally suitable candidates.

Stable vision:
Your glasses or contact lens prescription should have been stable for at least 12 months. Significant fluctuations or progressive deterioration in vision are generally contraindications for laser treatment.

Age:
You should be at least 18 years old (preferably over 20) so that your eyes are fully developed. Technically speaking, there is no upper age limit, but the benefits are greatest before the onset of presbyopia.

Corneal condition:
Sufficient corneal thickness is required to ensure that enough tissue remains and the cornea remains structurally stable. We check this during the brief examination.

General eye health:
Your eyes should be healthy. Mild dry eyes are not a contraindication; on the contrary, KLEx is often particularly suitable for people who suffer from dry eyes or contact lens intolerance.

Even those who are active in dusty environments for work or sports or contact sports often benefit from the flap-free method.

If some of these points are not met, this does not automatically mean that we cannot help you.

In many cases, there are alternatives: If KLEx is not an option for you, Femto-LASIK or the insertion of an artificial lens (ICL) could be considered, for example.

We will advise you honestly and in detail about your personal options. However, your safety is always our top priority:

We only recommend KLEx if everything is right.

KLEx treatment is performed on an outpatient basis and takes only a few minutes per eye. You will be awake the entire time, but we can give you a mild sedative if you wish.

Before we begin, we will carefully examine your eyes. We will measure your corneal thickness, pupil size, and visual defects, among other things, so that we can program our laser with the highest precision for you individually.

On the day of the operation, please arrive without contact lenses, without makeup, and well-rested.

With KLEx (and all other laser eye surgery procedures), both eyes are treated in a single session. This is standard practice, safe, and much more convenient for you, as it allows you to see clearly with both eyes.

The femto laser used in KLEx surgery fixes the eye in place and gently presses it into the eye socket in order to create as flat a cut as possible. This prevents the eye itself from moving.

During the treatment, we will talk to you and guide you through the individual steps. Many of our patients are surprised at how quickly and unspectacularly everything goes.

Immediately after the operation, you can relax with us while we discuss the aftercare once again. We will then schedule your first follow-up appointment, and you will receive an emergency number that you can use to reach us at any time.

Since your vision may still be somewhat blurry immediately after the laser treatment, we recommend that you arrange for someone to pick you up or have someone accompany you.

On the day of the operation, it is normal for your eyes to water a little, burn, or feel as if there is something in them. Thanks to the gentle nature of the procedure, there is usually no pain.

At home, it is best to rest with your eyes closed.

You will come to us for your first follow-up appointment the day after the operation. At this point, most patients already have good visual acuity of around 60%. It takes about a week to reach 100%, and then we will see you again.

In the first few hours immediately after the operation, your vision will still be somewhat cloudy or blurred, but this will quickly clear up.

The day after the laser treatment, most people feel ready to resume their daily routine, i.e., they can read normally again and return to work.

However, we recommend that you take at least the day of the surgery and the following day off work and rest your eyes during this time.

For your safety, we will discuss with you during the check-up the next day when you can start driving again.

The improvement in vision achieved by KLEx is permanent. The treated refractive error or astigmatism does not usually return, and the result remains stable for life.

In rare cases, a small portion of the corneal tissue may regenerate, resulting in minimal residual refractive error. Experience shows that this mainly affects patients with very high initial diopters and usually occurs within the first few months. If your visual acuity is not completely satisfactory over time, there is the option of follow-up treatment. YOUSEE will cover the cost of such corrective procedures for you, provided they are medically indicated.

We are only satisfied when you are.

However, no laser eye surgery can stop the natural aging process: from around the mid-forties onwards, the lens in the eye becomes less flexible in most people due to age. This condition, known as presbyopia, means that at some point you will need reading glasses, even if your distance vision remains sharp.

A KLEx procedure cannot prevent presbyopia.

However, there are solutions for this (e.g., monovision), which we will be happy to tell you about when the time comes. The important thing is that you can now experience freedom from your glasses.

99.4% of YOUSEE patients are happy with the results of their laser eye treatment and enjoy a new attitude to life full of spontaneity and comfort.

The correction achieved by laser eye surgery is generally permanent.

“What is the best laser eye surgery procedure?”
This is a question we are often asked, and the answer? There is no one best procedure, but there is the best procedure for you. In this section, we will discuss the advantages and disadvantages of KLEx.

Once you have laser treatment, you will be able to see at least as clearly as with your visual aids.
Fogged-up glasses, slipping contact lenses: all that is a thing of the past, and you can enjoy your new quality of life!

The laser incision made during this procedure is only 2 to 4 mm in size, leaving the stability of the upper corneal layer intact.

Since far fewer nerves are severed in the corneal surface, the risk of dry eyes is lower than with the other two procedures. Only a few patients report a foreign body sensation in the first few days.

Thanks to anesthetic drops, the procedure is completely painless, and the eye usually remains free of discomfort in the days following the procedure. Vision returns very quickly: often, around 60% vision is restored the very next day, and 100% vision is achieved after about seven days.

If you participate in a lot of sports, especially contact sports or outdoor activities, KLEx is a good choice. An accidental blow to the eye poses no risk: the outcome of the surgery will not be affected, as no flap can be displaced.

The KLEx laser eye surgery procedure offers patients who wish to have laser eye surgery a gentle and effective correction of their vision impairment. Without flap incisions, with fast healing and few side effects, it combines all the advantages of modern laser technology. KLEx is particularly suitable for people who value safe, comfortable, and fast treatment.

KLEx is the least invasive of all laser eye surgery procedures: the laser creates an opening measuring just a few millimeters, and serious complications are very rare. However, it is still a surgical procedure on the eye.

Although the vast majority of our patients are completely satisfied, it is important to us that you make a well-informed decision for or against laser eye surgery:

As successful as KLEx is, no reputable doctor can guarantee a completely perfect result. In very rare cases, a slight residual visual impairment may remain. Follow-up treatment can usually correct this, but a minimal residual need for vision aids cannot be completely ruled out.

Temporary side effects include dry eyes, sensitivity to light, and glare in the dark. However, these only occur in the first few days and weeks after the operation and then disappear on their own.

The KLEx procedure does not protect against natural age-related vision loss. This means that from around the age of 40, you will probably need reading glasses, even if your distance vision is and remains perfectly corrected. This is not a result of the surgery, but rather the normal passage of time.

In summary, the advantages of KLEx far outweigh the disadvantages:
No wonder the procedure is becoming increasingly popular.

Of course, we will discuss all the advantages and disadvantages with you in advance and address your individual situation so that you can make a well-informed decision at your leisure.

Although they are very rare, there is a possibility of complications with any surgical procedure. Serious problems are extremely rare with KLEx. Your safety is always our top priority: We carry out particularly extensive preliminary examinations in order to further minimize risks.

Possible risks at a glance:

In very rare cases, slight scarring of the cornea, known as haze, may occur after the operation. This clouding is caused by tissue reactions during healing. However, with KLEx, the risk of corneal clouding is very low, as the laser only creates a tiny opening.

Haze can be treated with eye drops and will then recede. Only in rare exceptional cases is it necessary to smooth out the clouding later with a procedure. YOUSEE takes preventive measures so that you hardly need to worry about this.

Despite careful planning, in rare cases it may happen that the desired visual acuity is not achieved exactly. Under-correction would mean that a slight residual visual impairment remains, so that you may still need weak glasses, while over-correction leads to slight hyperopia. This may cause reading to be temporarily perceived as somewhat strenuous. Such cases are very rare, occurring in less than 10% of cases. Incidentally, the success rate of YOUSEE is above the global average.

The risk of infection during laser eye surgery is very low anyway (less than 1%), as the procedure is performed under sterile conditions and we administer prophylactic antibiotic eye drops. If you follow our aftercare recommendations and do not forget to use the eye drops, the risk is further reduced.

Serious complications leading to significant and permanent vision loss are extremely rare (in the per mille range) with KLEx.
Blindness can never occur.
It is important that you follow all aftercare recommendations and, if in doubt, come in for an additional check-up.

We do everything we can to ensure that you achieve the best possible result without complications. However, if something unexpected does happen, we are always there for you and can help quickly and effectively.
Your eye health is always our top priority.

A word about the responsibility of laser eye surgery centers:
In a comprehensive test (2024), Stiftung Warentest emphasized the importance of careful preliminary examinations and transparent consultations before laser surgery.

We take this responsibility very seriously.

You can rest assured that we will only treat you if we are convinced that it is safe and appropriate in your individual case.

Please do not hesitate to ask us critical questions.
We will be happy to answer them: in detail, on an equal footing, and in a way that is easy to understand.

You may have heard of alternative laser eye surgery procedures, such as Femto-LASIK or Trans-PRK: but how do these procedures actually differ?

Important: When performed correctly, all common procedures yield similarly good results in terms of visual quality. The difference lies primarily in the procedure itself and the healing time. Here is a brief overview:

In Trans-PRK, the top layer of the cornea, known as the epithelium, is removed and the underlying cornea is shaped using a laser. This procedure does not require any incisions, but it does require a longer recovery time as this layer has to grow back. It takes longer to achieve full visual acuity than with KLEx.

In short:
Trans-PRK works on the outside of the cornea, while KLEx works on the inside.

This makes KLEx gentler, and the tiny incision heals faster.

Trans-PRK is gentler on the corneal structure, but healing is painful in the first 48 to 72 hours. In addition, the technology behind KLEx is more complex, making Trans-PRK the more affordable procedure.

In Femto-LASIK, a laser is used to prepare a thin corneal flap, which is then replaced. In KLEx, on the other hand, the correction is performed through a tiny opening on the side of the eye. Only a laser is used in both methods.

Both methods are very safe, and the eye heals very quickly in both cases.

Advantage of KLEx: There are no flap-related complications such as slippage of the flap, and dry eyes are less common.

Advantage of Femto-LASIK: Femto-LASIK can be used to treat a wider range of visual impairments, and the procedure is less demanding and therefore less expensive.

Important to know:

All of the laser procedures mentioned, Trans-PRK, Femto-LASIK, and KLEx, have the same goal and consistently achieve it in suitable candidates. The visual results are equally good after six months at the latest for all procedures.

There is no single best procedure, but there is the best procedure for you:
Together, we will find it.

Perhaps you have already been interested in offers abroad, such as laser eye surgery in Istanbul, which at first glance appear to be significantly cheaper.

This is completely understandable, after all, everyone wants to find a good solution at a fair price. But this is about something particularly valuable: your eyes and your vision.

Therefore, price should not be the only deciding factor. More important are the experience of the surgeon, the laser technology used, and, above all, personal aftercare that you can rely on at any time.

Germany and Switzerland have very high medical standards, giving you the assurance that quality, hygiene, and patient protection are paramount - without compromise.

The desire to save money is understandable of course, but we repeatedly see patients coming to us after inexpensive procedures abroad with uncertainties, unsatisfactory results, or even complications, and only then seeking the security and support they deserved from the outset.

Our suggestion for you:
Take the time for a non-binding, free* brief examination with us. We will listen to you, answer your questions, and calmly show you all your options, without pressure, but with respect and support for your decision.

* Free consultation by our trained, non-medical specialist staff.

One of the most common concerns among patients is the cost of treatment. Since health insurance companies in Germany and Switzerland classify refractive laser surgery as a voluntary, self-pay service, patients usually have to pay for KLEx laser eye surgery themselves. Statutory health insurance companies do not cover the costs, but private health insurance companies often reimburse part of the costs, depending on the tariff: it is worth inquiring individually. But what amounts can you expect to pay?

Important: At YOUSEE, all preliminary examinations, the surgery itself, and all follow-up checks are included in the price, not only for KLEx, but for all procedures.

Transparency is very important to us: with us, you will know in advance exactly what costs you will incur, with no hidden fees or surcharges.
You will also not be charged for any follow-up treatment if you are not satisfied with the result.

You can find the costs for a KLEx on our cost overview page.

Finally, we would like to address some frequently asked questions that we encounter time and again during consultations. Can't find yours? Contact us or drop by: We are happy to take the time for you.

Feel free to schedule a free* consultation appointment with us and together we will find out whether KLEx is the best procedure for you. By the way, the appointment is not only free*, but also non-binding. We advise, you decide: at your leisure and without pressure.

* Free consultation by our trained, non-medical specialists.

The KLEx procedure is a particularly gentle and safe method of laser eye surgery. It does not require a large incision, which significantly reduces the risk of complications. Many patients report that they found the procedure painless and uncomplicated.

The entire procedure is precisely planned, over quickly, and performed by our experienced specialists, who are there for you at all times. So you can rest assured that your eyes are in the best hands in a calm and trusting atmosphere.