Keratoconus treatment

New methods of Keratoconus treatment available in Knezović Eye Clinic.

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ATHENS PROTOCOL A modern way of treating keratoconus – a unique service

Keratoconus is a degenerative cornea disease whose cause is not fully known and most commonly affects the younger population. When the patient discovers signs of keratoconus, the disease is usually advanced, and the cornea is flat, weakened, and irregular. To stop progressive keratoconus or post-LASIK corneal excitation, it is often necessary to have an additional procedure to improve patient’s visual acuity. One of the most recent and most successful treatment methods is the Athens Protocol.

The originator is Dr A.J. Kanellopoulos, a renowned refractive surgeon and professor at New York University.

What is the “Athens Protocol”?

Athens Protocol is a therapeutic procedure made for normalizing the corneal surface or reducing the diopter, irregular astigmatism and thus significantly improving visual acuity, and is particularly effective for stopping the progression of keratoconus and correcting the consequences of the disease.

Keratoconus is successfully treated with this method. According to research by Kanellopoulos, the Athens Protocol has reduced the need for corneal transplantation in keratoconus in Greece for an amazing 90%.

How does the procedure of Keratoconus treatment look like?

The procedure begins with the initial “flattening” of the corneal surface by a laser treatment by phototherapeutic keratectomy (PTK), which removes the epithelium of the cornea. It is then subjected to a so-called “topo-guided”, topographically guided ablation, i.e. a partial PRK (TGP). This procedure greatly reduces the micro-irregularities of the surface of the eye to a point that does not compromise the patient’s safety. With Excimer laser is only treated layer of thickness up to 50 micrometers to maintain the mechanical corneal structure, which is further enhanced by simultaneous corneal crosslinking (CXL) application.

The procedure combines TGP and CXL at the same time, thus achieving a synergistic effect that these two procedures performed at different times do not achieve. The TGP operation itself provides effective normalization of the corneal surface, which directly improves functional vision. If the TGP is executed after CXL, the TGP operation partly abolishes the CXL efficiency. However, if TGP is performed at the same team i.e. just before the CXL, as in the Athens Protocol, it then allows deeper penetration of riboflavin (and UVA air) into the cornea, thereby achieving greater modulation of covalent connections collagen and significantly enhancing corneal strength due to enhanced cross – linking of collagen fibers deep in the sternum of the cornea. Besides that, combining these two procedures significantly reduces postoperative recovery time and patient absence from job.


The Allegretto Eye Q laser platform – a precondition for the success of the project is modern laser technology and a “secret recipe” – a prof. Kanellopoulos’s nomogram database

Is the procedure safe for the patient?

All the steps are carried out under the special control of a premium topographer, so-called Scheimpflug camera that does not allow excessive ablation and loss of tissue, which could harm the patient. Laser that’s conducting Athens protocol is also great for wavefront optimized myopia (up to 10), hyperopia (up to +6) and astigmatism treatments (up to 5 diopters).


Oculyzer – Pentacam. The whole procedure is under control of the Scheimpflug camera, so that remodeling of the tissue remains solely within the limits of the permissible values


What is achieved with the procedure?

After this procedure, the cornea gets more regular contours, reduces the diopter, improves visual acuity and makes it easier to adjust to contact lenses if needed.

Is procedure painful?

The whole procedure is completely painless, it is done in local anesthesia (droplets, without injection) and with preparation the of patient is finished in about 2 hours.


Results after the Athens Protocol:

As a medical institution that has the greatest experience in the field of performing such and similar (topographic) operations, we can boast of excellent results after the Athens Protocol.


Our presentations at the international congress (ESCRS – European Society of Cataract and Refractive Surgeons) in London 2014.

First Author: I. Knezovic


Most of our patients sees significantly better after the Athens protocol, some of them even so much that they do not need glasses or contact lenses anymore. This is impressive because most of them have been condemned for further decay of visual acuity, they were suggested to wear semi-solid contact lenses (which can aggravate the condition in the progression phase) or they are suggested only a corneal cross linking (epi off method) after which vision isn’t significantly improved.

Below are topographic pictures of some of our patients. The left image shows the corneal surface before the procedure, the image in the middle after the procedure (significantly more correct form!), and the right image shows the ablation profile, i.e. the laser correction / regularization treatment. These results are presented at several professional congresses in Croatia and abroad, and were also published in the form of an original scientific paper in the journal Acta Clinica Croatica.



Keratokonus - nove metode



Keratokonus - nove metode




Keratokonus - nove metode

 References about Athens protocol (for those who want to know more):

  1. J Refract Surg. 2014 Feb;30(2):88-93. doi: 10.3928/1081597X-20140120-03.

Keratoconus management: long-term stability of topography-guided normalization combined with high-fluence CXL stabilization (the Athens Protocol). Kanellopoulos AJ, Asimellis G.

  1. J Refract Surg.2011 May;27(5):323-31. doi: 10.3928/1081597X-20101105-01. Epub 2010 Nov 5.

Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial trans epithelial PRK and collagen cross-linking: the Athens protocol.  Kanellopoulos AJ1, Binder PS.

  1. J Cataract Refract Surg.2014 Oct;40(10):1597-602. doi: 10.1016/j.jcrs.2014.02.036. Epub 2014 Aug 28.

Epithelial remodeling after partial topography-guided normalization and high-fluence short-duration crosslinking (Athens protocol): results up to 1 year. Kanellopoulos AJ1, Asimellis G2


Can Athens protocol be done in Croatia?

Thanks to the advanced laser technology that makes it possible to properly do the procedure of Keratoconus treatment, special nomograms constructed by Kanellopoulus’s many years of work and the personal friendship and collaboration of Dr. Knesic and Prof. Kanellopoulus there is no longer need to go to America or Athens. It will suffice to just sign up and come to examination in our polyclinic.

The data of each patient is personally analyzed by Kanellopoulos and in agreement with Dr. Knezović optimal operative procedure is precisely defined.

International specialist co-operation in the field of keratoconus treatment and laser visual correction. In the picture prof. A.J. Kanellopoulos (right) and sc. Igor Knezović (left)

Who is a good candidate for such an examination?

If you have a problem with an unregulated or unstable diopter, keratoconus or someone in your family has similar problems, you are a good candidate for this type of specialist examination. Many years of experience and the latest technology are available to you in Zagreb at Knezović Vision Group Polyclinic, Ulica grada Vukovara 269f, tel. 01/66 77 222.


 Corneal cross linking

Cross-linking has become a standard method for stopping keratoconus and various corneal ectasia, either running alone or within the Athens protocol.


The goal of the procedure is to increase the degree of collagen connection in the cornea to restore satisfying mechanical stability.

At Knezović Polyclinic we use a polyvalent UVA VEGA lamp to adapt to each patient individually.

Before the procedure the outer part of the cornea (epithelium) is usually removed – the EPI OFF method, in several ways:

  • With alcohol (very rarely)
  • With laser (Crete protocol)
  • With a Pallikaris microbrewer


If the epithelium is not removed then it is EPI ON method – it is performed in special cases and in combination with other methods.

With extra-thin corneas, we use so-called. Contact lens assisted CXL – a crosslinking method with a contact lens that is soaked with riboflavin (a special type of lens and riboflavin), thus allowing the method to be performed on very thin corneas. As curiosity, we mention that we are the first polyclinic in Europe to undertake this procedure.

Since corneal cross-linking is different for each patient, especially if performed under the Athens protocol, it is necessary to provide several types of riboflavin during irradiation in order to have an adequate corneal “drip” on the one hand, and on the other hand a sufficient thickness and to preserve the deeper parts of the eye from undesirable effects of radiation. The threshold for photochemical damage caused by free radicals for endothelial cells is 0.35 mW / cm2. In all our procedures, the goal is to keep the aforementioned irradiation at a twice as lower value so that the procedure is completely safe for the patient.

The types of riboflavin (vitamin B2) we use in the Knezović polyclinic:

  • isotonic
  • hypotonic
  • trans epithelial
  • With dextrane
  • Without dextrane
  • For contact lenses imbibition


Our presentation at the international congress (ESCRS – European Society of Cataract and Refractive Surgeons) in Istanbul 2015.


During the procedure, the corneal thickness is monitored and, if necessary, irradiation protocol is changed, depending on the individual deviations. Prior to the operation, UV lamp is regularly calibrated with UV meter. Radiation MUST be strictly controlled and homogeneous, without “hot spots”, as this may lead to side effects.

From all of the above, it is obvious that corneal cross-linking, whether performed independently or within the Athens protocol, is not a “one for all” procedure, but an individualized and algorithmically tailored procedure for each patient separately. Only with such approach can the patient achieve the maximum effect after surgery, which can now be checked trough the level of connection of collagen fibrils in the cornea.


Demarcation lines at the anterior OCT after Cross linking / Athens protocol, as an indicator of success of surgery


The action is completely painless and comfortable for the patient. After the surgery, therapeutic contact lens is applied for 3-4 days and therapy with antibiotics and anti-inflammatory drugs in the form of droplets. The length of the therapy depends on the diagnosis.

According to some research, the cornea after the Athens protocol / cross linking becomes 380% stronger and progression of the disease is reduced by 97%. The action is almost never repeated.


 Cross-linking references (for those who want to know more):

  1. Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat LE. Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg 2008;34(5):796-801.
  2. Caporossi A, Mazzotta C, Baiocchi S, Caporossi T. Long-term results of riboflavin ultraviolet a corneal collagen cross-linking for keratoconus in Italy: the Siena eye cross study. Am J Ophthalmol 2010;149(4):585-593.
  3. Wittig-Silva C, Whiting M, Lamoureux E, Lindsay RG, Sullivan LJ, Snibson GR. A randomized controlled trial of corneal collagen cross-linking in progressive keratoconus: preliminary results. J Refract Surg2008;24(7): S720-725.
  4. Hersh PS, Greenstein SA, Fry KL. Corneal collagen crosslinking for keratoconus and corneal ectasia: One-year results. J Cataract Refract Surg 2011;37(1):149-160.

Knezović Polyclinic invites all persons who have problems with keratoconus or some other corneal ectasia to contact or visit us in order to prevent the spread of the disease.


Intracorneal rings


Intracorneal rings, rings are small devices implanted in the cornea to change the diopter or are used in the treatment of keratoconus.



For all the questions fell free
to call us 01 / 66 77 222

Where are we?

Poliklinika Knezović

Green Gold Business Center, Tower V1, 8th floor

Ulica grada Vukovara 269f

10000 Zagreb

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