ELZA’s role in Eye Laser Surgery

Members of ELZA not only perform refractive laser surgery. They perform research, both clinical and laboratory based, to improve current technology, and they teach and educate on an international level multiple times every year.

The ELZA co-founder Prof. Farhad Hafezi is one of the associate editors of the US-based “Journal of Refractive Surgery”, the most important journal for refractive surgeons, and currently the highest ranked specialty journal in ophthalmology. In this role, he is constantly exposed to the latest developments in the field.

Besides, Prof. Hafezi serves as one of two european ophthalmologists on the Advisory Board of GlobalONE, the educational platform of the American Academy of Ophthalmology.

The patient greatly benefits from all this, because he/she is not treated by a simple „user“, but rather by a team that helps shaping the future of refractive surgery.

An eye surgeon undergoes his own LASIK

Refractive laser surgery has nowadays become a very safe and effective procedure. Nevertheless, every operation carries a residual risk, and the patient has to trust the doctor’s ability to keep him/her safe..

A question that patients ask their treating physician frequently is: „Doctor, would you undergo LASIK or PRK yourself?“

Our doctors did: the ELZA member Prof. Farhad Hafezi wore contact lenses for more than 20 years. He progressively developed dry eye, a condition typical after so many years of uncomplicated contact lens wear. In 2007, he underwent his own LASIK surgery, and is free of glasses and contact lenses ever since. See the video of his operation below.

The Chapters

Visual Disorders
Trans-PRK & Femto-LASIK
Treat Presbyopia
Refractive lens surgery, Bioptics
Complication management

Posts on Eye Laser Surgery published by ELZA

ELZA at the 2018 ATMO Eye Meeting in Tunisia

ELZA in Tunisia: ELZA founder Farhad Hafezi gives ... Read more

Growing the Refractive Surgery Market: Better Outcomes and Big Data

Prof. Hafezi an a video interview with EyeWorld at ESCRS ... Read more

ELZA at ESCRS 2018

The ELZA Institute's surgeons and researchers spent four ... Read more

Fixing your SMILE: how do you reoperate, and what are the consequences for corneal strength?

Other vision healthcare professionals regularly refer patients to ... Read more

ELZA at „Science2Clinix“ in Bangalore, India

Speaker Schedule Hafezi
The Narayana Nethralaya Hospital in Bangalore, India has ... Read more

ELZA at SAMIR 2018 in Tanger

SAMIR 2018
The ELZA Institute was represented at the 2018 ... Read more

SmILE biomechanically more solid than flap-based laser surgery

SmILE provides a biomechanically more solid residual cornea ... Read more

Visual Disorders


The human eye captures optical stimuli and transmits them to our brain. Like a camera, it possesses an optical system and a photosensitive layer. The optical system of the eye consists of the cornea and the crystalline lens, the cornea being responsible for two third of the refractive power, the crystalline lens for one third.

If the eye is “too long”, the condition is called myopia and if it is “too short”, the visual error is called hypermetropia. In European countries, 15-20% of the population are considered myopic and 5% hypermetropic.

Normal vision (Emmetropia)

When the eye (cornea and crystalline lens) deviates light rays in a way that the focal point is located on the retina, the eye is without visual error. A person with normal vision is capable of clearly and distinctly recognizing objects at close as well as at far distance.

Nearsightedness (Myopia)

When the focal point is located in front of the retina, the eye is called myopic. This is generally due to an eye that is physically longer than normal. Objects at far distance are perceived unclear. When observing a distant object, the optical system projects the image in front of the retina. On the contrary, objects at close distance are clear.

Farsightedness (Hypermetropia)

When the focal point of the eye is located behind the retina, the eye is called hypermetropic. This is generally due to an eye that is physically shorter than normal. Until approximately 45 years of age, hypermetropia can be corrected with accommodation byfrom the crystalline lens for far vision and sometimes also for near vision. This accommodative power however decreases with the age and a hypermetropic adult must often wear glasses. Over the age of 45 years, objects at near and far are perceived as unclear.


When a person is astigmatic, the focal point of the eye is scattered because of irregularities in the corneal curvature, the cornea looking more like an american football rather than a perfect sphere. Astigmatism is often paired with myopia or hypermetropia. To correct astigmatism, variations of the refractive power between different corneal meridians have to be compensated.

Aging Vision (Presbyopia)

Young people usually have good vision at near and at distance: they can observe a landscape and read newspapers. The human crystalline lens has an elastic capacity that allows it to adapt to various distances (accommodation). With age, the lens becomes hard and rigid, its elasticity decreases. This process is called loss of accommodation and is inevitable. This change of vision linked to aging is natural and concerns every adult starting at 45 years of age. Currently, it is not possible to restore lens elasticity.

Trans-PRK and Femto-LASIK (Z-LASIK)

Besiders classic methods of visual correction such as glasses and contact lenses, a number of surgical methods and modern procedures to allows to reduce or completely compensate for the visual defect.

Glasses: Glasses are the most widely used means of correction and remain an excellent tool for many forms of ametropia. They may however narrow the visual field when myopia is important.

Contact lenses: They provide a good means of correction and are generally well-tolerated for a number of years. With the years, many people become intolerant to contact lenses: wearing them becomes uncomfortable and the risk of infections increases.

PRK: photorefractive keratectomy with an excimer laser. This method allows correcting myopia up to -5 diopters, hypermetropia up to + 4 diopters and astigmatism up to -3 diopters. The most modern variant of PRK is transepithelial PRK (Trans PRK), where the epithelium is ablated by the excimer laser.

LASIK: in-situ laser keratomileusis, also performed by an excimer laser, is more patient-friendly than the above-mentioned procedure. It can correct myopia up to -10 diopters. The most modern variant is Femto-LASIK, where the thin corneal lamella needed for the procedure is created by means of a femtosecond laser.

Trans PRK

Photorefractive keratectomy (PRK) has been introduced into ophthalmology in 1988. It is the „oldest“ of the methods used in refractive laser surgery. The postoperative results, however, are absolutely comparable to newer methods like LASIK.

PRK, in contrast to LASIK, has a lesser impact on corneal biomechanics. PRK is preferred over LASIK in cases where corneal biomechanics may be compromised.

The newest variant of PRK is trans-PRK, where the corneal epithelium is removed not mechanically, but also with the means of a laser. This makes trans-PRK a true „non-contact“ refractive laser procedure.

The Femto-LASIK procedure

A femtosecond laser, positioned with great precision on the eye cuts a very thin layer (a flap) of 100 to 130 micrometer (0.1 millimeter) thickness into the cornea. The flap remains attached to the cornea at one side, which is used as a hinge. Light pulsations of a computer-guided excimer laser result in the vaporisation of certain areas of the corneal surface. Modern lasers with scanning spot technology allow for remodelling of the corneal surface in a few seconds and with submicron precision. When the refractive defect has been corrected, the operator repositions the flap, which will heal naturally.
Normal aspect of the cornea minutes after surgery.

Z-LASIK (Femto-LASIK with the Ziemer Femtosecond Laser)

Z-LASIK represents the most modern version in LASIK surgery. It enables the surgeon to precisely position the flap on the corneal surface, and change the position by micrometers, if necessary

Limits of treatment:
myopia, hyperopia, and astigmatism

The limits of treatment greatly depend on the integrity of the cornea, and its biomechanics. Our institute is massively involved in research related to corneal biomechanics, so we have a deep understanding of the risks, but also of the advantages a remodelling can give. Limits are individual, but in general, the excimer laser can correct for myopia up to -8.0D, hyperopia up to +5.0D, and astigmatism up to 7.0D.

Treat Presbyopia: PresbyMAX μ-Monovision

Some facts about presbyopia

Presbyopia is not a visual defect but refers to the natural, age-related changes in the lens of the eye. It loses flexibility and the eye becomes unable to adjust clearly to different distances (accommodation).
As our entire body ages, so do our eyes. Presbyopia becomes subjectively detectable between 40 and 45 and stagnates at approximately 65 years of age. Presbyopia occurs in people with normal vision as well as in those with visual defects.

What treatment options exist?

Until recently there was no satisfactory treatments to restore reading for people with presbyopia. Although both multifocal contact lenses and the insertion of an artificial lens are generally considered, both of these frighten off many people – be it because they cannot tolerate contact lenses or because they do not want to undergo complex eye surgery. The new PresbyMAX μ-Monovision procedure offers a minimally invasive alternative.

How does PresbyLASIK with PresbyMAX μ-Monovision work?

PresbyMAX μ-Monovision is based on the proven, well-established and successful PresbyMAX procedure, in which bi-aspheri- cal, multifocal ablation profiles are applied. In principle, the most up-to-date treatment method, PresbyLASIK, is carried out just like every other form of LASIK. First, a special laser or microkeratome is used to prepare a wafer-thin layer of cornea (flap), which is then folded away to expose the underlying corneal area for laser treatment. The SCHWIND AMARIS then precisely models the cornea with very fast laser pulses.
However, in contrast to conventional LASIK, similar to the principle of multifocal contact or intraocular lenses, several exactly calculated focal points are generated in the eye. After the laser treatment, the flap is folded back to its original position.
The entire treatment takes only a few minutes, the ablation itself only a few seconds.


How is PresbyMAX  μ-Monovision different from other procedures?

Prior presbyopia treatments with the excimer laser aimed to divide the work between the eyes: One eye is sharpened for distant viewing, the other for near vision (monovision).
PresbyMAX and PresbyMAX μ-Monovision represent the next generation. Whilst with PresbyMAX both eyes contribute equally to visual acuity, the newest technology, Presby- MAX μ-Monovision, ensures that the dominant eye focuses slightly more on distance and the non-dominant eye focuses slightly more on near vision.
The advantage for you: A high depth of field and very high visual quali- ty at all distances. Three-dimensional vision is retained. No other laser technique for the cor- rection of presbyopia available on the market offers such a comprehensive range of treatments for the most varied indications.

Who can be considered for treatment?

Patients who are exclusively presbyopic and wish to do without reading glasses.
Presbyopic patients with uncorrected myopia, hyperopia or astigmatism.
Presbyopic patients who have already undergone laser treatment with the goal of optimal distance vision and have had a good experience with it.
Presbyopic patients who have already undergone cataract surgery and now wish to be able to read without corrective lenses.

Is PresbyMAX μ-Monovision suitable for me?

We will be able to answer this question after a thorough assessment of your eyes.

Refractive Lens Surgery, Bioptics

Refractive lens surgery means either the addition of a lens into the anterior chamber of the eye (phakic lens), or the replacement of the natural lens (refractive lens exchange). Bioptics is the combination of lens surgery with refractive laser surgery. We typically use it in complex optical situations.

Phakic lenses

Phakic lenses are additional lenses that are placed in the anterior chamber of the eye, either in front of the iris (i.e. Artisan lens) or behind it (ICL). We use phakic lenses in patients younger than 45 years with a high degree of refractive error (i.e. myopia starting at -7.0 D).

Refractive lens exchange

In patients that are older than 45 years of age, and presenting with a high degree of refractive error (i.e. myopia starting at -7.0 D), we prefer to replace the existing lens with a bifocal, trifocal, or multifocal lens. These options allow for good vision for both near and far.


Under certain circumstances, we combine refractive laser surgery and lens exchange. An example would be a patient with a high degree of myopia, and a very high astigmatism at the same time. Sometimes, we can choose a special (toric) intraocular lens to correct for both. In other instances, we need to remove the myopia part with the lens, and the astigmatism part with the laser.


It is nowadays possible, with the right technology and strategies and surgical experience at hand, to correct almost every degree of refractive error. Sometimes, more than one intervention is necessary to achieve the final goal.

Complication management, therapeutic refractive laser surgery

Complications in refractive laser surgery may occur both during surgery, but also in the aftercare. Often also, an improper diagnosis and treatment planning before the operation is at the origin of complications. For example, post LASIK ectasia is most often encountered, because a subclinical ectasia or irregularities in corneal biomechanics had not been detected prior to surgery.

This surgery is called Therapeutic Refractive Laser Surgery. The aim here is not to free a patient from glasses or contact lenses, but rather to regularize the cornea, improving vision that can otherwise not be improved with glasses/contact lenses.

Small / decentered optical zones

In the 1990s, the excimer technology used still had slow eye tracking systems. Under certain circumstances, the optical zones created on those corneas were either too small, or not centered to the pupil. Nowadays, we are able to repair those corneas, as you may see in the example below.

Irregular astigmatism

Irregular astigmatism occurs when the surface of the cornea is uneven or asyymetric. Causes may be multiple, including inflammation, trauma, disease, and previous surgery like keratoplasty. Repairing irregular astigmatism cannot be standardized, it rather requires an individual approach in each case.

Ectasia after LASIK

Can be handled using corneal cross-linking. See here.

Epithelial ingrowth

The cells of the corneal surface have the ability to divide and multiply (stem cells). If these cells enter the flap interface during surgery, they might create complications later on. A number of techniques have been developed to eliminate epithelial ingrowth after LASIK.


It is nowadays possible, with the right technology and strategies and surgical experience at hand, to handle almost all complications encountered in refractive laser surgery. However, repairing a complication requires a high level of experience and is a customized approach in all cases. Sometimes, multiple surgeries are necessary to re-establish good quality of vision.


Before the procedure

We use the latest technology available. For the creation of the flap, we use a femtosecond laser from Ziemer technologies: the Z6 PowerPlus is currently the most advanced flap-maker, and is a swiss product. The excimer laser treatment is performed with the Schwind AMARIS,  a latest state-of-the-art laser from Schwind eye-tech solutions.
The preoperative exam will be performed by the optometrist and your surgeon. It is of utmost importance that your surgeon learns about the particularities of your eye prior to surgery. This greatly increases the safety of the procedure.
You should refrain from wearing your contact lenses for two full weeks prior to the pre-examination. This is necessary to precisely assess the refractive error of your eye. Wearing contact lenses, even for a few hours only, would  interfere with the precision of the measurement, and the precision of the surgery.

After the pre-examination, you may wear your contact lenses until the day before the surgery.

Please count for 1.5 hours. We will dilate your pupils, so you should not come by car. Also, do not plan any important meetings the next day, since your pupil might stay dilated up to 24 hours, making it difficult to read.
The same surgeon who has performed the preoperative exam will also perform the treatment.
Both LASIK and PRK take approximately 30 minutes. This includes the preparation time.

The surgery itself takes a few minutes only, and the laser ablation a few seconds only.

LASIK: We usually operate both eyes in the same session.

PRK: We operate in two sessions, leaving one week in between the surgeries. This is due to the slower healing in PRK.

Yes. The long-term results of PRK and LASIK are absolutely comparable. In general, and if the eyes allow for it, we prefer to perform LASIK procedures, because of the greater comfort for the patient. If medical reasons speak for a PRK, then vision will be compromised for a few days, when compared to LASIK.
We use eye drops for local anesthesia. This is fully sufficient for the entire procedure.

The procedure

Only an eye care professional can determine whether or not an individual is eligible for LASIK treatment. In general, a good LASIK candidate is at least 18 years old, has healthy corneas, and has maintained a stable eye prescription for the last 12 months. Because hormonal levels can affect the shape of the eye, women who are pregnant or nursing should not undergo LASIK treatment. The procedure should also not be performed on patients who:

  • Have glaucoma, cataracts or dry eyes
  • With collagen vascular, autoimmune or immunodeficiency diseases
  • Show signs of keratoconus (an eye disorder in which there is thinning of the cornea that results in blurred or distorted images)
  • Take medications with ocular side effects (such as Accutane® or Cordarone®).
We will choose the best method for the individual eye. This depends on a number of factors like corneal thickness, corneal topography, degree of refractive error, the hormonal status.
The FDA recognizes LASIK as proven, safe and effective. According to guidelines recently released by the Eye Surgery Education Council (ESEC), fewer than 1% of patients who have received LASIK to date have experienced serious, vision-threatening problems. Most LASIK complications can be treated and usually resolve within several months of surgery. There are no known cases of blindness resulting from LASIK.
Although no one knows the exact number of complications, studies suggest that the incidence of minor difficulties such as dry eyes and nighttime glare is around 3% to 5% from combined LASIK and PRK procedures. These minor complications include:

  • Halos – Some patients will notice glare, halos or starburst around objects in low-light conditions. For the vast majority, these symptoms are temporary. However, others will continue to experience them for several months or longer. During pre-operative evaluation, the refractive surgeon can determine whether or not a person is at high risk for seeing long-term halos.
  • Dry eyes – There is increased dryness of the eyes typically for several months following LASIK, though some patients may experience dryness for a longer period of time. It is important to use lubricating drops frequently. If the eyes remain dry for prolonged period, there are other drops or techniques that can help. Pre-operative evaluation will help determine whether or not a person is a likely candidate for experiencing dry eyes.
  • Infection – This is an extremely rare occurrence, with a 1 in 2000-3000 chance (similar to any eye surgery). Fortunately, as the LASIK technique has developed over the years and proven to be of great benefit to millions of patients nationwide, firmly established protocols now exist which minimize the risk of infection.
Before a surgeon will perform LASIK, preoperative tests are performed to screen for glaucoma, cataracts and other disqualifying conditions. The surgeon may also use an instrument called a corneal topographer to photograph and electronically map the eye in order to gather more information about the individual’s eyes prior to treatment.


Because contact lenses change the shape of the cornea, LASIK candidates are required to switch to eyeglasses before their baseline evaluation is taken and continue wearing only eyeglasses between 2-4 weeks before LASIK surgery. Not leaving contact lenses out long enough for the cornea to assume its natural shape before surgery can cause inaccurate measurements and poor vision after surgery

LASIK: The procedure is painless, however, most people experience 4-6 hours of mild irritation after their LASIK procedure.

PRK: The procedure is painless, however, most people experience pain during the first 48 hours after the procedure, during the healing of the corneal epithelium.

LASIK: In most cases, people can return to work within 1-3 days following LASIK surgery. Excluding the day of surgery itself, people may begin driving as soon as they see well enough. Women can start wearing makeup within two to three days of treatment, however, they are advised to wear only new cosmetics in order to decrease risk of infection.

PRK: Vision is blurred, and the cornea can be painful during the first three days following the surgery.  You should refrain from driving during the first week after surgery.Women can start wearing makeup at one week after the surgery, however, they are advised to wear only new cosmetics in order to decrease risk of infection.

The vision correction is permanent. However, a person’s vision may change naturally with time and LASIK does not affect visual conditions that may develop with age. Also, LASIK does not prevent presbyopia and the eventual need for reading glasses. Depending on the cause, retreatment may be a viable solution to later vision changes, and other treatment options also exist.