Cross-linking as new technology for keratoconus treatment
What is keratoconus?
The cornea of a healthy person’s eye is spherical in shape. Keratoconus is a disorder resulting from dystrophy and thinning of the cornea tissue. Instead of being spherical (which is the norm), the cornea adopts a conical shape. Due to this conical shape of the cornea, light rays are refracted differently at different points and this reduces vision acuity (as in case of myopia). The person with keratoconus sees distorted images of objects and jagged lines (as in case of astigmatism). In later stages of keratoconus, the cornea is thinned out to the point of rupture and causes pain. Patients complain that they have to change glasses very often and cannot tolerate soft contact lenses.
Until recently, the only method of treatment for keratoconus was keratoplasty – a surgical procedure on the cornea aimed at restoring its shape and functions. The operation is based on the replacement of damaged sections of the cornea with the donor transplant. Since December of 2010, Excimer Eye Clinics in Moscow and Nizhny Novgorod have introduced a new method of keratoconus treatment, which is cross-linking.
What is the essence of the cross-linking method?
The cross-linking method was invented by Professor Theo Zeilor. The idea is to strengthen the cornea and stabilize the keratoconus using a special laser. In the course of this treatment, additional chemical ties are created between the collagen fibers (that form structural frame of the cornea) and they strengthen the mechanical density of cornea. Thus new cornea fibers are formed and they are criss-crossing. The cornea becomes denser and is able to retain its shape preventing further progress of keratoconus.
The Excimer Eye Clinics perform keratoconus treatment with the cross-linking method on an out-patient basis as a ‘one-day’ procedure. The cross-linking takes less than an hour.
The stages of cross-linking
- General drop anaesthetic is administered and special instruments are used to remove the outer layer of the cornea – the epithelium.
- A solution of ribophlavin (vitamin B2 in the solution of dextrane T500) is dropped on the cornea every 5-10 minutes within a 30 - minute period.
- Within the next 30 minutes, the ribophlavin drops are combined with laser exposure of the cornea.
- A protective contact lens is then placed on the eye of the patient to be removed in 2-3 days. During the next week, the patient is instructed to use special eye drops.
The use of the cross-linking method allows to strengthen the stroma of the cornea, to stabilize keratoconus progress, stop thinning of the cornea, and what is more important – to avert the necessity of transplanting the cornea (keratoplastic).
Now patients with keratoconus and a thinned cornea may undergo cross-linking simultaneously with laser correction for refraction anomalies. The decision to perform the cross-linking procedure alone or in combination with laser correction is made by the doctor on the basis of a comprehensive diagnostic testing.
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