Treatment of corneal cone
How to avoid corneal transplantation? Modern Cross-Linking
Corneal cone is a progressive eye disease that leads to thinning and distortion of the cornea, with subsequent deterioration of vision – myopia and astigmatism and often hypersensitivity to light.
The degenerative and progressive nature of the disease means that patients are forced to change the power of their eyeglasses frequently, yet they do not experience significant improvements in vision quality.
The corneal cone affects both eyes in the vast majority of cases, although usually the severity of the disease is asymmetrical and rarely fully equal in both eyes.
Causes of corneal cone formation
Although the condition is encountered quite frequently, the causes of the disease are still largely unclear and, as usual in such cases, an inherited predisposition is pointed to. Possible causes include enzymatic changes in the epithelium, the upper layer of the cornea, metabolic disorders, but also infections and trauma.
The disease often manifests itself during adolescence, in most cases before 30. year of age. It can progress in stages, and experience shows that it progresses fastest between 30. a 50. year of age. Men get the disease twice as often as women. The incidence of corneal cone is about 1: 2000 in the general population. The disease is one of the most common causes of corneal transplantation.
However, corneal transplantation is carried out only when all other treatments are no longer satisfactory. These include hard contact lenses, crosslinking, epikeratoplasty and intraocular rings.
Risk factors that predispose a patient to corneal cone include:
- excessive rubbing of eyes with hands
- Genetic factors (6-19% of cases)
- Spontaneous congenital defects of the visual system or defects manifested in the course of diseases such as Down syndrome, Alpost syndrome, Marfan syndrome and Ehlers-Danlos syndrome
- Complications related to the presence of allergies and atopy
- Eye diseases – retinal pigmentary degeneration, retinopathy of prematurity, spring conjunctivitis and keratitis
- enzymatic imbalance
- Excessive exposure to UV rays, including sunlight
- ill-fitting and carelessly applied contact lenses and associated eye friction.
Course of the disease
In the initial stage of corneal cone, correction with glasses or contact lenses is sufficient. The earlier the disease appears, the more likely it is to progress. The corneal deformation steadily increases, the cornea becomes thinner and thinner, and may fracture, at the site of which a scar will form.
Deterioration of vision, manifested m. in. The perception of halos, rings of light, which are formed especially around lamps and other light sources, as well as shadows or streaks, forces the patient to constantly change his eyeglasses or contact lenses. The corneal cone first appears in one eye, but over time the disease reveals itself in the other eye as well. The course of the disease varies greatly from patient to patient.
In about 20% of cases, the disease progresses rapidly to the point that, due to the pronounced bulging of the cornea and the scarring that develops on it, glasses and contact lenses no longer serve their purpose.
However, there are some patients for whom the diagnosis is made late, although the too rapid deterioration of vision (the refractive power of the cornea increases by about one diopter in one year) and the difficulty in selecting a satisfactory correction should prompt a diagnosis of cone.
Symptoms and diagnosis of corneal conus
The symptoms of corneal cone are nonspecific (progressive deterioration of vision, blurring of vision, hypersensitivity to light, burning and redness of the eyes) and it is easy to underestimate the ongoing disease process. Therefore, if there is a family record of corneal cone cases, you need to insist on diagnostics in this direction. Attention should also be paid to the situation in which the patient’s myopia progresses too quickly in adolescence, he complains of a halo effect/phenomenon around the light source and blurring of the image, and subsequent changes of glasses are not effective.
Corneal cone diagnosis includes:
- in-depth interview
- evaluation of distance visual acuity
- keratometry (measurement of the curvature of the cornea)
- retinoscopy (examination of the refractive state of the eye)
- slit lamp examination of the cornea
- corneal topography
They are a non-invasive and painless test.
To assess the condition of the patient’s eyes, a comparison is made between the results of an individual corneal topography, such as from a year ago and from the current examination. Depending on the changes that have occurred during this time, measures are taken to stop the changes occurring in the cornea.
Corneal cone therapy proceeds in two stages:
- Stopping the progression – and in some cases reversing – of lesions.
- The aim is for the patient to achieve the greatest possible visual acuity. If the corneal relief is small, soft contact lenses are used, when the relief is large hard lenses come into play.
Cross-Linking
CROSS-LINKING (named after the effect it produces) – also known as cross-linking of bonds, cross-collagenization of the cornea or CXL – causes stiffening of the cornea and increases its mechanical resistance. The stiffening of the cornea is accomplished by increasing the number of bonds between the collagen fibers that build it. It occurs under the influence of UVA irradiation of the cornea.
In order to increase the sensitivity of the superficial layers of the cornea to UVA radiation, it is soaked in a special photosensitizing substance, riboflavin (vitamin B2). Clinical studies confirm that the action of riboflavin contributes to slowing or stopping the disease and, in some cases, its regression. The procedure thus avoids corneal transplantation.
Until recently, corneal transplantation was considered the only valid treatment for advanced corneal cone. However, it is not a simple procedure, and there is also a risk of graft rejection.
The long healing process means that significant improvement in vision is only achieved after two years. Since corneal transplants are also used in young patients with progressive corneal cone, this always involves high demands on the transplant. Meanwhile, CLX does not require such deep intervention in the structure of the eye or the use of foreign material. Cross-linking the cornea allows it to stabilize and halt the progression of the disease.
In the case of corneal crosslinking, by hardening the cornea, further progression of its abnormal protrusion can be prevented. Thus, the deformation cannot be reversed, only “frozen” in the stage it is in at the moment. At the same time, it cannot be guaranteed that the treatment will have a positive effect. The increase in visual acuity is again most often made possible by wearing a rigid contact lens. This does not hinder the possibility of a possible lens transplant at a later time, regardless of its causes.
It is important to know that:
- If the procedure is performed on a very thin cornea, damage to the deeper layers of the cornea is possible, which can lead to corneal opacity.
- In individual cases, such as with possible keratitis due to treatment, the cornea becomes cloudy, which may be accompanied by increased sensitivity to light for several weeks. This can lead to temporary incapacity under certain circumstances. In exceedingly rare cases, even deterioration of vision is possible. These turbidities can cause the need for a second treatment, which in many cases improves the situation.
In the case of certain systemic diseases (e.g., rheumatic conditions, atopic dermatitis) or for other reasons unknown to us, the healing process may possibly be impaired or delayed.
The course of the operation
The treatment is preceded by preparation of the patient, consisting of washing the face with a disinfectant. After that, the patient gets local anesthesia, in the form of an injection or application of special eye drops, and his eyelids are immobilized for the operation. The surgeon removes the upper protective layer of the cornea and administers riboflavin drops, which remain in the eye for approx. 30 minutes.
This is followed by a 10-minute UV irradiation of the cornea, after which the patient is given a soft dressing contact lens. Their function is to protect the eye during recovery. After surgery, the patient receives drug treatment to prevent inflammation and reduce postoperative pain. The protective lenses are removed by the surgeon after a few days.
Preparation
The first step is to disinfect the facial area. The patient is given anesthesia in the form of eye drops or an injection. The next step is to immobilize the eyelids. The entire preparation for the procedure is completely painless.
Riboflavin drops
The procedure begins with the removal of the upper protective layer of the cornea, the epithelium. Special riboflavin drops are then applied to the eye for 30 minutes.
UV radiation
The administration of riboflavin drops is followed by a 10-minute irradiation of the cornea with UV light.
Postoperative phase
The final step is to protect the eye after surgery with soft lenses and drug treatment to prevent inflammation and reduce postoperative pain. The protective lenses are removed after a few days by the surgeon. That’s it!
