Keratoconus is a degenerative, bilateral, progressive eye disease that leads to thinning and deformation of the cornea, with severe vision impairment.
How Does This Disease Occur?
Onset is in adolescence, initially in one eye, then in both eyes, accompanied by decreased vision. The natural evolution is slow, over the next 10-20 years, leading either to severe corneal thinning or to stabilization and cessation of progression.
The causes of keratoconus are not fully understood. Studies show that there is a qualitative impairment of collagen fibrils in the corneal stroma, leading to thinning and cone-shaped bulging in the lower part of the cornea. This bulging induces progressive irregular astigmatism, with distorted perception of images.
Among the causes that lead to keratoconus are considered:
- genetic factors – it has been found that 1 in 10 patients have this disease in their family
- allergies and atopy
- excessive eye rubbing – appears to play an important role in disease development
- systemic connective tissue disorders (Ehlers-Danlos syndrome, Marfan syndrome)
- endocrine diseases (thyroid)
What Are the Symptoms of Keratoconus?
At first, vision decreases in one eye, later the other eye will also be affected. Usual activities like reading and driving at night become difficult (halos appear around light sources). In advanced stages, increased sensitivity to light appears, and the patient perceives double or triple images.
The patient frequently changes glasses, and when these no longer improve vision, rigid contact lenses are needed. In late forms, tolerance to these lenses also decreases, with the patient having major difficulties in carrying out usual daily activities.
Usually, vision quality decreases slowly, but there are also rare situations where this occurs suddenly, dramatically, leading to corneal scars that permanently affect vision.
How is Keratoconus Diagnosed?
The ophthalmologist may suspect the presence of keratoconus during a routine examination, at the biomicroscopic examination of the patient and by measuring the corneal curvature using the autorefractometer.
Definitive Diagnosis
It is made by corneal topography, a non-invasive investigation that takes a few seconds. The corneal topograph is a device that analyzes the map of the anterior part of the cornea, measuring its curvature in different meridians. The specific topography appearance in keratoconus helps stage the disease, from stage I to stage IV.
Pentacam
In recent years, with the help of this device, subclinical stages of keratoconus can be diagnosed, which cannot be evidenced by ordinary topography. The Pentacam is a high-resolution tomograph that provides extremely important details of the cornea, analyzing both its anterior and posterior parts. At onset, keratoconus affects the posterior part of the cornea.
Specular Microscopy
It is indicated for evaluating corneal endothelium cellularity.
Corneal Pachymetry
Represents the measurement of corneal thickness; it is indispensable for guiding the therapeutic strategy at each stage of the disease.
How is Keratoconus Treated?
In the initial phases of the disease, vision can be improved with glasses. Disease progression leads to the need for frequent diopter changes.
In more advanced stages, when the corneal shape is greatly modified, special rigid contact lenses are needed, which smooth out the ocular surface. They manage to significantly improve image perception. Both glasses and contact lenses serve to improve vision, not to stop disease progression.
Keratoconus treatment can also be performed by implanting intra-stromal corneal rings, which serve to flatten the corneal surface, improving the patient's vision.
In recent years, the appearance of corneal crosslinking has revolutionized the treatment of this condition, serving to stabilize disease progression. Practically, with the help of ultraviolet A rays and riboflavin (vitamin B2), the corneal structure is strengthened, preventing further deformation.
In advanced stages of the disease, where vision is very low due to extensive scars, or when the degree of corneal thinning is pronounced with risk of perforation, corneal transplant is necessary. Fortunately, early diagnosis and adequate treatment with corneal crosslinking have made the number of cases requiring transplant decrease significantly in the last 20 years.
What is Corneal Collagen Crosslinking?
The basic mechanism of crosslinking is the formation of covalent bonds at the level of collagen fibrils and adjacent proteins in the corneal stroma. These new bonds strengthen and stiffen the corneal structure, thus increasing its stability.
Two important steps are involved in crosslinking. In the first step, the riboflavin solution (vitamin B2) is applied to the cornea following a special protocol. Subsequently, a lamp emitting ultraviolet A rays is used, which promotes the photopolymerization reaction between riboflavin and collagen in the stroma. The result is strengthening of the bonds between collagen fibers, thus increasing the mechanical resistance of the cornea. The treatment effect depends on the degree of riboflavin penetration through the epithelium into the stroma. The better the penetration, the stronger the effect of forming new bonds between collagen fibrils.
Crosslinking Techniques
EPI-OFF Technique
It is a standard procedure that consists of applying vitamin B2 after removing the corneal epithelium (the most superficial layer), thus promoting riboflavin penetration into the corneal stroma. This technique is effective but is accompanied by pain, slow healing, risk of corneal scars and infection.
EPI-ON Technique
The corneal epithelium is preserved, over which riboflavin is applied directly; it has comparable efficacy to epi-off and is much better tolerated by patients, especially when it comes to children. In this case, the risk of infection after the procedure is significantly reduced.
At the Clario ophthalmology clinic, we use both crosslinking techniques for treating progressive keratoconus. The procedures are performed with a state-of-the-art Swiss crosslinking device, the Peschke Platinum 330.
The treatment is performed under local anesthesia and can be done on both eyes in the same session. The effect on disease stabilization is observed in the following months after the intervention, evidenced by corneal topography.
The Indications for This Type of Treatment Are:
- stages I and II of the disease (in certain situations also for stage III)
- corneal thickness over 400 microns
- transparent cornea, without scars
- disease progression evidenced topographically in the last 6-12 months
It is important to emphasize that the role of crosslinking is to stabilize keratoconus progression, not to improve vision, although this can be observed in some situations. Usually, tolerance to wearing contact lenses increases, thus improving the comfort and quality of vision for patients.
If you have vision problems or recognize yourself in the keratoconus symptoms listed above, we are waiting for you at an ophthalmology consultation at Clario!
Frequently Asked Questions
Keratoconus is a degenerative, bilateral, progressive eye disease that leads to thinning and deformation of the cornea, with severe vision impairment.
Treatment includes glasses (initial stages), rigid contact lenses (advanced stages), intra-stromal rings and corneal crosslinking for disease stabilization. In severe cases, corneal transplant.
Crosslinking strengthens the corneal structure by forming covalent bonds at the level of collagen fibrils, using riboflavin (vitamin B2) and ultraviolet A rays.
It is indicated in stages I and II (sometimes III), with corneal thickness over 400 microns, transparent cornea without scars, with progression evidenced topographically in the last 6-12 months.
