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Pentacam – indispensable diagnostic tool for keratoconus
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Oculyzer – Pentacam. The whole procedure is performed under the control of the Scheimpflug camera, so that remodeling of the tissue remains within the limits of the acceptable values.
KERATOCONUS TREATMENT
What is keratoconus?
Keratoconus is a degenerative disease that affects the front surface of the eye called cornea. In patients suffering from keratoconus, progressive thinning, weakness and corneal irregularities lead to worsening visual acuity (shortsightedness and irregular astigmatism). There is a visual blur, appearance of ghost images and light sensitivity.
Keratoconus – Causes
The exact cause of keratoconus is unknown, but is considered to be associated with poorer enzyme activity within the cornea. There is a genetic predisposition, as it is more common in families where keratoconus has already been diagnosed. Approximately, the incidence of keratoconus is one person per two thousand (5-8% in Down’s syndrome patients).
When does keratoconus appear?
Unlike most other eye diseases keratoconus affects the younger population. It is often diagnosed with adolescents in their 20s. Younger age groups are the most endangered when it comes to disease progression, and if keratoconus is not treated, it can progress in 3rd and 4th life decades. It occurs equally in both sexes.
Keratoconus – how to recognise the symptoms?
Keratoconus is very difficult to identify in the early stage without proper ophthalmic examination equipment (Pentacam analysis). The most common symptoms a patient can recognise are appearance of double-images, increased sensitivity to light and eye squeezing. Most people have the need to rub the eyes vigourosly and to squeeze the eye in order to sharpen the image, which may lead to progression of the disease itself. Keratoconus can also be recognized by the fact that after a while, glasses may not improve the visual acuity any more.
Keratoconus – Progression of the Disease
Keratoconus most commonly develops asymmetrically and in 90% of cases it affects both eyes. There are no rules on how the disease will progress, this differs from patient to patient. Keratoconus progression may take 10 to 20 years and in some cases may be life-long if not treated.
Keratoconus – treatment
In most cases, contact lenses are prescribed, in order to sharpen the visual acuity and to allow patients normal participation in everyday activities. If keratoconus is not treated properly in time, it may progress until it causes permanent loss of vision and in some cases the only therapeutic option remains the corneal transplantation. Nowadays, there are less and less such cases due to advanced technology that allows diagnosis of keratoconus at an early stage- At Knezovic Eye Institute, keratoconus is successfully treated with the latest methods of DISC protocol, Crosslinking (CXL) and the Athens Protocol.
Is it possible to do the refractive surgery if I have keratoconus?
If you have keratoconus, it is not possible to remove the diopter by standard methods, as this may lead to progression of the disease itself and decompesation of the cornea, which ultimately leads to a worsening of the visual acuity. If you want to correct your visual acuity (remove your diopter) and you have keratoconus, the best therapeutic option is the Athens protocol, which allows you to “take off the diopter” (actually regularizing cornea´s surface with few special laser procedures) as much as your corneal configuration permits it and also fix the cornea to stay stable after surgery.
ATHENS PROTOCOL
Athens Protocol is a therapeutic procedure which goal is normalising the corneal surface, i.e. to reduce the refractive error, irregular astigmatism and thus significantly improve visual acuity, and is particularly effective in halting the progression of keratoconus and avoiding the consequences of the disease.The Athens Protocol for the treatment of keratoconus was first performed in Greece. Keratoconus is very successfully treated with this method. According to research of professor Kanellopoulos, the Athens Protocol, reduced the need for corneal transplantation in keratoconus in Greece for almost 90%.
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How does Athens Protocol look like?
1. STEP – Phototherapeutic keratectomy (PTK)
The procedure begins with the initial“smoothening”of the corneal surface by laser treatment called phototherapeutic keratectomy (PTK), which removes the epithelium of the cornea.
2. STEP – “TOPO-GUIDED” LASER ABLATION
The cornea is then subject to partial topographically guided (“topo-guided”) ablation (TGP). This procedure greatly reduces the microirregularities of the surface of the eye to a point that does not compromise the patient’s safety. Excimer laser is only treats thickness up to 50 micrometers to maintain the mechanical corneal structure, which is further firmed by corneal crosslinking (CXL).
3. STEP – CROSS LINKING (CXL)
Cross-linking has become a standard method for stopping keratoconus progression and various corneal ectasias (thinning), whether performed independently or as a part of the Athens protocol.
In addition to this, the advantage of this method is certainly a fact that it has shown good results in the treatment of infectious ulcers and other corneal diseases resistant to some of the standard treatment methods.
The goal of the procedure is to increase the degree of crosslinked collagen in the cornea to restore suitable mechanical stability. Currently, the exposure applied is 5.4 mJ / cm2 worldwide, with different irradiation levels of 3-30 mW / cm2. So, the greater the irradiation, the shorter the duration of the procedure. Of course, this has its limits, because corneal cross linking is also dependent on the oxygen, which is necessary during the process itself and this requires a certain amount of time. This is why it is very important which UVA lamp and what type of riboflavin is used by the practicing physician.
In the Knezovic Eye Institute we use a multifunctional UVA VEGA lamp to approach each patient individually. The time spent under UVA-light varies between 10 and 30 minutes.
Before the procedure the outer part of the cornea (epithelium) is usually removed – the EPI OFF method, in several ways:
• alcohol (very rare)
• by laser (Crete protocol)
• with Pallikaris’s surgical rotating brush
If the epithelium is not removed then it is EPI ON method – it is performed in special cases and in combination with other methods.
In the case of extra-thin corneas, we use the so-called “Contact lens assisted CXL” – a crosslinking method with a contact lens that is soaked with riboflavin (a special kind of lenses and riboflavin), thus allowing the method to be performed in very thin corneas. Interestingly, we are the first polyclinic in Europe to perform this procedure.
Since corneal cross-linking is different for each patient, especially if performed as a part of the Athens protocol, it is necessary to provide more types of riboflavin, to ensure adequately “soaked” cornea on one hand, and on the other hand, to have sufficient thickness and to preserve the deeper parts of the eye of unwanted effects of irradiation.
The threshold for photochemical damage caused by free radicals for endothelial cells is 0.35 mW / cm2. In all our interventions, the goal is to keep the aforementioned irradiation twice less this value, so the procedure is completely safe for the patient.
Is the Athens Protocol Safe for the Patient?
All steps are carried out under special control of top-level topographers, so-called Scheimpflug camera that does not allow excessive ablation and loss of tissue, which could harm the patient. Laser that performs Athens protocol is also great for wavefront optimized treatments of shortsightedness (up to -10 diopters), farsightedness (up to +6 diopters) and astigmatism (up to 5 diopters).
What is achieved with the Athens Protocol?
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 the Athens Protocol Painful?
The whole procedure is painless, it is done in local anaesthesia (eye drops, no injection) and together with preparation of the patient it lasts for about 2 hours.
Who is a good candidate for such an examination?
If you have a problem with an poor or unstable vision, keratoconus or someone in your family has had similar problems, you are a good candidate for this type of specialist examination.
Is the Athens Protocol better than the Cross-linking?
With the Athens Protocol, more accurate contours are achieved, refractive error is reduced, visual acuity improved and it is easier to fit the contact lenses if they need to be worn after the surgery while with cross-linking only – the cornea is strengthened but these other effects are not achieved.
Was the operation painful and should I stay in the clinic after the surgery?
The entire procedure is completely painless, it is done in local anaesthesia (eyedrops, without injection). The complete procedure with the preparation of the patient lasts about 2 hours (for one eye). During the procedure the patient is awake and communicates with the surgeon all the time. Immediately after the procedure a therapeutic lens is placed on the cornea and it serves as a protection and it helps corneal surface to heal faster. After the procedure, the patient gets all the necessary therapy and goes home where he has to rest and avoid any adverse conditions until the first check-up, scheduled 3 days postoperatively.
How long does it take to recover after the procedure?
Three days after surgery, most of the patients return to their daily activities. If you work in unfavourable microclimate conditions (wind, dust, smoke) it is desirable to stay home for the next 7 to 10 days. The cornea may change during the first year due to vitamin supplements and collagen fixation until it gets its final shape. If necessary, 1-2 months after the procedure the contact lenses may be prescribed for the best visual acuity.
IGOR KNEZOVIC, MD, Ph.D. – KERATOCONUS EXPERT
Thanks to the advanced laser technology which makes it possible to properly do the procedure and special nomograms constructed by Dr. Kanellopoulus’s many years of work and personal friendship and collaboration between Dr. Knezovic and Prof. Kanelopoulus, patients no longer need to go to America or Athens to undergo this surgery. The data of each patient is personally analysed by dr. Knezovic, who has carried out over 2000 Athens Protocols in his career, and is therefore visited by patients from all over the Europe.
