What is Keratoconus?
Keratoconus is the most common degenerative and progressive change in the cornea, characterized by non-inflammatory thinning of corneal tissue, which takes on a conical shape. It affects approximately one in two thousand individuals and is more common in men than women. It occurs in all populations worldwide, although it is more prevalent in certain ethnic groups.
The exact cause of keratoconus is still unknown, but it is thought to be associated with poor enzymatic activity within the cornea itself. Genetic predisposition has also been established as it more frequently appears in families where keratoconus has already been diagnosed. The progression of keratoconus is faster in patients with Down syndrome. It is believed that the disease usually affects both eyes, but most often one eye has a more pronounced progression of the disease. It usually progresses during adolescence and then stabilizes (although this is not the rule).
Keratoconus can be diagnosed in four stages (grades), with the first representing the mildest form of the disease, and the fourth the most severe (often requiring corneal transplantation).
What are the symptoms of Keratoconus?
The basic symptom of keratoconus is a unilateral decrease in visual acuity due to progressive myopia (short-sightedness) and astigmatism, which becomes irregular. The main sign is central and paracentral thinning of the corneal stroma (it takes a conical shape).
Keratoconus Treatment Methods
Treatment of mild and moderate cases of keratoconus consists of wearing glasses and semi-hard or hard contact lenses, with regular monitoring of disease progression. For progressive forms of the disease, the corneal collagen crosslinking method (CXL) is recommended. Patients who tolerate lenses well are often satisfied with their vision, while patients with advanced stages of keratoconus, those who cannot wear lenses, and those with visual acuity below 30%, as well as patients with pronounced thinning of the cornea, are candidates for corneal surgery. If the cornea has become decompensated and has irretrievably lost its transparency, then perforative corneal transplantation is the only method of choice for these patients. The best techniques used for diagnosis and monitoring of disease progression are OCT-optical coherence tomography of the front part of the eye and Pentacam-computerized corneal topography.
What is corneal collagen crosslinking?
Corneal collagen crosslinking (CXL) is a procedure that attempts to strengthen the weakened collagen bonds of the cornea and thus slow the progression of keratoconus. The emphasis is on the word “slow”, as the procedure has been used in the world for about 20 years, so there is still not enough time gap to be able to determine with certainty that crosslinking definitively stops keratoconus. According to current experience, out of 5 patients who have undergone this procedure, one has had to undergo corneal transplantation. People recommended for crosslinking are patients with keratoconus whose corneal thickness is not below 400 microns, patients whose cornea is clear and without scars, and those whose values of the steeper corneal meridian are a maximum of 58 diopters, and visual acuity with glasses can be 90%, or lower. Patients with other corneal diseases, and of course pregnant women, are not candidates for crosslinking.
How is the crosslinking procedure performed?
The cross-linking procedure lasts about half an hour to 45 minutes. It is done under local anesthesia with drops and is completely painless. Using a gentle instrument, the epithelial layer is removed from the surface of the cornea, and the cornea is treated with high doses of B2 vitamin in the form of a thick liquid called Riboflavin for 20 to 30 minutes. Riboflavin here has a multi-purpose role. First of all, it strengthens the cornea, but it is equally important that it protects the deeper segments of the eye from UV rays, which the eye will be treated with later. After the end of the instillation of B2 vitamins, the cornea is treated with a UV lamp for the next half hour or 10 minutes (depending on the protocol applied), with breaks after every five minutes. The lamp automatically turns off and Riboflavin is instilled again during a two-minute break. After the end of the procedure, a soft contact lens is applied to the treated cornea, which continuously stays in the eye for 4 to 7 days. The patient is given local therapy in the form of corticosteroid drops which will be instilled over the next two months. The patient may feel pain on the first day after the procedure, which they are definitely warned about. The real results after crosslinking are evaluated 6 to 12 months after the procedure in adult patients, and in children up to 24 months are needed. The patient can continue to wear contact lenses after recovery, and very often these are lenses with the same parameters as before crosslinking.