What is Keratoconus?
Keratoconus is the most common degenerative and progressive change in the cornea,
characterized by non-inflammatory thinning of corneal tissue, which then 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. 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, while most often one
eye has a more pronounced progression. 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 (shortsightedness) 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
gas permeable (RPG) contact lenses, with regular monitoring of disease progression.
For progressive forms of the disease, corneal collagen crosslinking (CXL) is
recommended. Patients who tolerate lenses well are often satisfied with their vision,
while patients with terminal stage of keratoconus with visual acuity below 30%, as well
as patients with pronounced thinning of the cornea, are candidates for corneal
transplantation surgery. If the cornea has become decompensated and has irretrievably
lost its transparency, then performative corneal transplantation is the only method of
choice for these patients. The best techniques used for diagnosis and monitoring of
disease progression is the corneal topography. Sometimes, in addition to this
procedure, the corneal optical coherence tomography (OCT) can be used as well.
What is corneal collagen crosslinking?
Corneal collagen crosslinking (CXL) is a procedure that attempts to strengthen the
weakened collagen bonds of the corneal stroma and thus slow the progression of
keratoconus. The emphasis is on the word “slow”, as the procedure has been used for
about 10 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. Patients recommended for crosslinking are those 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, while the 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 3o to 45 minutes. It is done under topical
anesthesia and is completely painless. Using a gentle instrument, the corneal epithelial
layer is removed, 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, 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 receive later during the
treatment. After the end of the instillation of B2 vitamins, the UV light is applied for the
next half an hour or only 10 minutes (depending on the protocol applied), with breaks
after every five minutes. The lamp automatically turns off and Riboflavin is instilled
again during the break. At 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 few
days. The patient may feel pain on the first day after the procedure, which they are
warned about earlier. The real results after crosslinking are evaluated 6 to 12 months
after the procedure in adult patients, and in children up to 24 months. The patient can
continue to wear contact lenses after recovery, and very often these are lenses with the
same parameters and same refractive power as before the crosslinking.
