This is defined as a progressive bilateral cornea degeneration in the shape of a cone, caused by a curving and narrowing mainly in the paracentral area, and less frequently in the central zone.
The specific cause of these corneal changes has yet to be established, although there are three classic effects which include: narrowing of the stroma, iron deposits in the epithelium and ruptures of the Bowman membrane.
It is still uncertain whether this effect is hereditary, and the majority of patients with keratoconus have no family history of development of the disease. Descendants only seem to be affected by keratoconus in 8% of cases.
The main symptoms begin during puberty or early adolescence, and the illness develops up until the third or fourth decade of life, in which it normally abates, although it can return at any moment.
Occasionally it can even appear later on in life, in which case it is less degenerative. Vision seems to be better, and there tends to be less astigmatism than in earlier ages.
Normal Eye Eye with keratoconus
Symptoms
During the initial stages, vision may only be slightly affected, causing glaring, sensitivity to light and irritation.
Keratoconus may be suspected when the patient displays frequent changes in the correction of his/her glasses, whereas these changes are less frequent with contact lens users.
The patient will display a blurred and distorted vision viewing images in one eye due to the asymmetrical development of the disease. This deterioration is due to refractive changes in the eye with keratoconus, general changes in myopia and astigmatism.
Both eyes can become affected, although normally, the degree of development is different. There seems to be a greater number of cases of unilateral keratoconus when found during the early stages. Contrastingly, the more advanced the ectasia, the greater the chance that it will be bilateral due to its progressive asymmetry.
Over time, the cornea will become narrower and will gradually deform, causing increasingly intense and irregular astigmatism, which can rarely be treated with glasses.
The prognostic can vary greatly, and in all cases, the progression can stop spontaneously.
As the disease progresses, the speed of deterioration varies in each patient; this can range from a rapid progression during early adolescence, to a slow development, in which symptoms are not displayed until a more advanced age.
Treatment
CORNEAL CROSS-LINKING
Corneal cross-linking is a non-invasive surgical treatment designed to stabilise the cornea and to slow or stop the progression of keratoconus.
This treatment consists of applying riboflavin and UV light to the cornea, with the aim of strengthening the cornea by increasing the number of bonds between the collagen molecules and reducing their elasticity.
This treatment produces no immediate change to the patient's sight, and in some cases it will not change at all; however, it does produce alterations in the corneal structure and, as a result, increases its stability.
We could summarise this technique as the treatment of the causes of keratoconus, but not as a correction of it.
From the studies published to date, this technique seems to improve the results achieved following the implant of intrastromal rings.
INTRASTROMAL OR INTRACORNEAL RINGS
This is a surgical treatment which involves the implantation of two semicircular segments of variable thickness and length. These are perfectly tolerated by the body without any risk of rejection, making this the safest modern treatment for certain stages of keratoconus.
The aim of implanting these intrastromal segments or rings is to correct the corneal irregularity which forms the keratoconus, while stopping the progression of the keratoconus and improving vision.
Simulation of the effect of intrastromal rings
The additional benefit of intrastromal rings is that they can be removed or replaced if they do not carry out their function correctly, or if they become intolerable, although there are very few cases describing intolerance to these segments.
CORNEA TRANSPLANT
This intervention is designed to replace the central part of the patient's cornea. These are quite common procedures, which often produce excellent results.
The probability of rejection is lower than with any other transplanted organ since the cornea does not contain blood vessels.
The cornea transplant is only recommended for cases in which the implantation of intra-corneal or intrastromal rings is not advised.
