Medical information gathered by Dr. Marco Abbondanza on experience with ophthalmologic surgery
What is keratoconus
Keratoconus is a corneal illness (non inflammatory progressive dystrophy) which progressively deteriorates affecting both young men and women. It normally appears during or immediately following puberty.
The problem becomes evident when the cornea bends outwards, deforming into a cone shape and thinning of the centre of the cornea happens. The refractive power of the cornea changes when this irregular curve appears, causing image distortion to occur (from low to high levels) as well as blurred vision both near and far.
The normal disposition of corneal proteins, which direct bright stimuli without encountering obstacles, is overwhelmed through these changes. Images are distorted and in some cases, scars, brought upon by changes in the disposition of corneal proteins, prevent light from filtering causing an annoying blinding feeling.
Studies show that keratoconus can be brought on by one or more of the following:
1) a congenital abnormality of the cornea caused by genetic changes. About 7% of keratoconus carriers have a family history of the illness;
2) an ocular trauma, such as rubbing eyes excessively or using contact lenses for many hours at a time and for too many years;
3) ocular illnesses such as pigmental retinitis, retinopathy of the premature or allergic keratoconjunctivitis;
4) systemic illnesses such as congenital Amaurosis of Leber, Down's syndrome, imperfect osteogenesis and Addison's disease.
Optical Correction
Initially, a visual impairment created by keratoconus (astigmatism), can be corrected through use of eyeglasses. Since astigmatism tends to deteriorate, special contact lenses designed for that kind of cornea must be used to gain better vision.
Finding the correct kind of contact lens can be very frustrating. An imperfect lens can damage the cornea and make it impossible to use even for very short periods of time. In some cases, the cornea slowly deteriorates until it becomes stable after some years with little damage. However, in more than 20% of cases, the cornea becomes extremely irregular and presents scars which make it impossible to use contact lenses.
Tests prove that although contact lenses better vision, they also speed up the deterioration of keratoconus.
CORNEAL CROSS-LINKING TREATMENT
Recently a new therapy for treatment of keratoconus has been introduced, this therapy is known as corneal crosslinking therapy but the same treatment is also referred to as CCL or C3-R.
The normal cornea consists of numerous layers of collagen fibers, with molecular links between the layers which are known as crosslinks. The aim of the treatment is to increase the strength and durability of the cornea by stimulating and thus increasing corneal crosslinking.
The procedure was first developed in Germany and clinical trials have been in course since the year 2000, in Italy clinical trials have been successfully performed more recently.
The technique is essentially quite simple. An eyedrop that consists of a solution containing riboflavin is applied to the eye and a carefully dosed quantity of UVA radiation is applied to the eye over a five minute period, the procedure is repeated 6 times for a total of 30 minutes of UVA exposition.
In the first trials the treatment was performed in eyes with initial keratoconus. The treatment aimed to increase corneal resistance, and thus, to essentially prevent evolution of keratoconus.
The excellent results following these initial cases of treatment allowed the extension of the treatment to eyes presenting different stages of keratoconus. The extent to which corneal cross linking is beneficial in different stages of keratoconus is dependant on a number factors, such as corneal thickness and the rate of evolution of the disease.
Dr. M. Abbondanza performs corneal crosslinking alone, or associated with mini asymmetric radial keratotomy.
Patients that are considered for treatment, must undergo an extensive clinical workup including computerized corneal topography, endothelial microscopy, ultrasound pachymetry, b-scan sonography, keratometry and biomicroscopy.
The most important clinical parameter that must be considered before treatment is corneal thickness, in fact, the cornea and also the riboflavin solution act as filters to UVA radiation. If the cornea is not sufficiently thick, necessary measures must be taken to reduce UVA penetration to the eye, such as placement of a corneal contact lens during treatment.
The possibility of associating MARK and corneal crosslinking offers the possibility to increase both visual acuity and corneal strength in many patients, in fact MARK has potential to increase visual acuity considerably in selected patients with keratoconus.
The ultimate goal in these conservative treatments for keratoconus patients is to postpone or possibly eliminate the necessity of penetrating keratoplasty, and to improve the quality of vision of patients as long as possible.
Technically, corneal crosslinking may be performed in two ways. The first consists in removing the most superficial layer of cells of the corneal epithelium before treatment. This technique guarantees the most complete absorption of the riboflavin solution into the corneal stroma, but the corneal epithelial removal may cause discomfort following treatment. This discomfort is very variable in patients and ranges from mild to moderate and is usually limited to the first 2 days following treatment, although a mild irritation may persist for a week until the epithelial layer of the cornea reforms. The symptoms are perfectly controllable by using analgesics, local non steroidal anti inflammatory treatment (FANS), and lachrymal substitutes associated with the placement of a corneal contact lens for the few days following treatment.
The second technique that is preferred by some Authors reduces patient postoperative discomfort by leaving the corneal epithelium in place, these Authors recommend application of riboflavin for a longer period to allow more time for absorption of the medication before the actual UVA application.
In conclusion, crosslinking is an extremely promising technique and offers a unique possibility to strengthen the cornea in patients with keratoconus. As with all medical procedures a complete pre- treatment individual ophthalmologic clinical examination is necessary to evaluate the opportunity for treatment. The results achieved by the ophthalmologists all over the world performing Crosslinking, prove an enduring stability and a thikening of the cornea after the treatment.
Cornea Transplant
In about 24% of cases, Keratoconus progressively evolves until it reaches a point where a cornea transplant must be done.
When is it necessary to face a cornea transplant?
When there is a severe thinning of the cone's summit or when central dull scars interfere with vision, , in order to improve their vision and in order to end pain caused by contact lenses, patients must undergo a cornea transplant.
Transplant can be either perforating or lamellar.
The so-called perforating transplant completely removes the central part of the cornea and substitutes it with a new cornea of a donor.
85-90% of perforating cornea transplants are totally successful. About 10-15% of those operated experience either acute or chronic rejection.
Rejection is caused by the antibodies of the patient, which consider the cells of the cornea donated as “strangers” and consequently they attack them, as they would do with bacteria and virus.
The rejection can be either acute or chronic, which means that it can occur either right after the surgery, or even after many months or years.
Patients will most likely need contact lenses after a transplant in order to attain satisfactory eyesight. 80% of those operated have 5/10 vision thanks to the use of contact lenses.
5-7% of those operated undergo acute rejection and must repeat the operation, hoping to achieve better results. All those who experience rejection of the cornea transplant have a much higher chance of a new rejection.
Another 5-7% of cornea transplant patients undergo chronic rejection of the transplant itself with acute crisis which can be partially kept under control through specific anti-rejection medication.
There is another less known aspect which must be dealt with.
The strip used in place of the unhealthy cornea does not have the same lifespan of the original cornea.
The donated cornea gets old quickly for a number of reasons, which are mainly the following:
The tissue belonged to a human being who died for reasons that do not interfere with the donation of organs and tissues, but the length of time between the death and the moment the organs or tissues were taken surgically from its donor, is extremely important. The more this interval is long, the more the cornea will be damaged. The liquid into which the corneas of the donor are kept after the surgery, contains nutritious substances and preservatives. Preservatives are very important, as they prevent bacteria and fungus from growing into the liquid itself. The more the cornea remains inside the liquid, the less it will be damaged.
For the above reasons the donated cornea lasts less than the original one.
This is also why it is important to wait as long as possible before transplanting a cornea, in the hopes that it will arrive from a young donor.
When lamellar keratoplastic is being done, only a part of the thickness of the cornea is removed, leaving the deepest layer. In this way, many risks of rejection are reduced, but new problems are likely to arise related to the quality of the patient's vision after the operation
In Italy cornea transplant is a particular case. The majority of corneas which are transplanted are needed by patients with keracotonus in such an advanced stage as to have no other means of curing it.
Lateley, in order to reduce the problems related to keratoplastic method, either perforating or lamellar, surgeons often prefer to perform the so-called conservative keratoconus surgery.
Can cornea transplant be avoided?
Of course.
If evolutionary keratoconus is operated during stages I and II of the illness, the cornea still maintains certain characteristics making conservative keratoconus surgery possible. Dr. Marco Abbondanza has dedicated much time to studying this illness. Since 1988, together with other colleagues, he has been working on an experimental technique which takes into consideration the possibility of correcting visual and non visual impairments related to this pathology. Through his vast experience with refractive incision surgery, he combined the ability of correcting myopic and astigmatic impairments of radial keratotomy to the natural structural intensification of scar tissue.
This modern technique consists in making small incisions on the cornea to correct astigmatic impairments created from distortion of the corneal lens caused by keratoconus.
This method corrected visual keratoconus impairments but could bring excessive flattening of the cornea causing a visual impairment contrary to the original one.
On the basis of these previous experiences, Dr. Abbondanza therefore created a new surgical technique called Mini Asymmetric Radial Keratotomy (M.A.R.K.).
M.A.R.K. flattens the cornea until it reaches physiologic effects, thereby reducing visual impairments that have formed as a cause of cornea deformation.
M.A.R.K. is performed only in the area where the keratoconus has developed. Both the flattening and the structural intensification of scar tissue take place only in the distorted zone.
The first result of this operation makes it possible for a person to lead a perfectly normal life.
The second and more important result is stopping the progression of the illness and in the worst cases, slowing it down.
The first operations were done in 1994 and routine check-ups show the equilibrium of the operated cornea.
Today many colleagues in Italy and all over the world use this surgical technique and are totally satisfied by the results.
Other surgeons have studied new operating methods, confirming the need to leave corneal transplants as a last resort.
In 1994, several American surgeons came up with a technique called I.C.R. Intra Corneal Rings. This operation consists in implanting into the internal part of the cornea, stiff plastic rings whose purpose is to strengthen the cornea in its weakest points. These rings act as a mechanical reinforcement of the unhealthy part of the cornea.
Early results are fairly satisfactory proving the necessity of operating during the early stages of the illness in order to guarantee good results.
Dr. Abbondanza has been studying a cure for keratoconus for twenty years and highly supports conservative keratoconus surgery.
Through personal experience, the creators of these methods have put together precise instructions for each technique. There is no such thing as a method capable of always giving excellent results for each type of keracotonus.
The surgeon must keep informed about different techniques available today and must choose the one to use for each patient who comes to him for help with their problem.
Therefore it's absolutely essential for the patient to undergo an accurate check-up by professionals having a long experience in refractive and keratoconus surgery.
The benefits of these new techniques can be attained only by carefully following these precautions.
However, Dr. Abbondanza, basing himself on his long personal experience, is now able to testify that the best of the results is achieved only with M.A.R.K. surgical technique, which is the only one that combines a strengthening of the cornea with the best possible optical correction.
