The only proven way to stop the progression of keratoconus is corneal collagen cross-linking (CXL).

Keratoconus: Causes, Symptoms and Modern Treatment

Questions about keratoconus are answered by ophthalmologist and ophthalmic surgeon specializing in the diagnosis and treatment of corneal diseases, Dr. Kateryna Kovryhina.

The cornea is a transparent “window” through which light rays enter our eyes and allow us to see the world. Keratoconus is a progressive, non-inflammatory, degenerative disease of the cornea that leads to thinning and a change of its normal spherical shape to a cone-like one. It predominantly affects young people and often results in a loss of vision that cannot be fully corrected with glasses or contact lenses, and in some cases requires corneal transplantation.

How common is keratoconus

In the last century, keratoconus was considered a relatively rare disease, with a prevalence of about 1:2000 in the general population. Today, the prevalence of keratoconus has increased by roughly 400% and is now estimated at about 1:500. This is thought to be largely related to environmental factors and indirectly to the growing number of laser vision correction procedures.

Why does keratoconus develop

The exact causes of keratoconus are still being studied. However, it is clear that heredity plays an important role.

At the pathogenetic level, researchers believe that a key factor is an imbalance of enzymes in the cornea. Their dysfunction leads to an increased production of free radicals such as superoxides, hydrogen peroxide and nitric oxide. These substances damage collagen bonds within the cornea, which weakens its biomechanical properties.

It is thought that patients with keratoconus are unable to neutralize the normal amount of free radicals that are produced in the corneal stroma in all people. This failure is due to insufficient activity of protective enzymes, including catalase and superoxide dismutase. As a result, free radicals accumulate and gradually damage the cornea.

Risk factors

Several genetic and non-genetic factors are considered responsible for this imbalance. Non-genetic factors include ultraviolet radiation, habitual eye rubbing, poorly fitted contact lenses and chronic eye inflammation.

Because of this, patients with keratoconus are advised not to rub their eyes, to wear sunglasses and to use properly fitted contact lenses.

How keratoconus progresses

Progression may theoretically continue throughout life, but more commonly lasts 10–20 years, after which the condition may stabilize or, on the contrary, lead to significant visual disability. The right and left eyes may be affected to a different extent. There is a clear pattern: the earlier keratoconus starts, the faster it tends to progress. The later it appears, the slower the progression usually is.

What may accelerate progression

Possible factors that may contribute to the progression of keratoconus include concomitant hypothyroidism and long-term treatment with corticosteroid medications. In children, pregnant women and breastfeeding women, keratoconus may progress more rapidly due to hormonal changes.

How keratoconus can be detected

In some cases, the patient can suspect a problem based on symptoms such as gradual, unexplained visual decline, ghosting or multiple images, double vision and increased light sensitivity. Often, patients can recall a specific period when these complaints first appeared.

Spectacle or contact lens correction may only partially improve vision or may fail to improve image quality at all. These symptoms usually appear in adolescence or early adulthood and can be mistaken for ordinary myopia, astigmatism or accommodative spasm or overstrain, remaining undiagnosed in a routine clinic setting.

The diagnostic equipment in our center allows us to detect keratoconus with a high degree of accuracy at early stages.

Diagnostic tools for early detection

After that, diagnosis depends on specialized, high-precision instruments, which are not available in every clinic, and on an experienced ophthalmologist. To detect preclinical stages of keratoconus and to confirm manifest disease, we use corneal topography or tomography, which provides a complete map of corneal thickness and refractive power at every point.

We often see abnormal or inconsistent autorefractometry data, new-onset corneal astigmatism or a marked increase in pre-existing astigmatism, as well as unusually high degrees of myopia that do not match other clinical findings.

How keratoconus is treated

At the current stage of medical development, there is no method that can completely cure keratoconus. However, in 1993, the technique of corneal collagen cross-linking was introduced and has since been refined. Today there are several international protocols for performing this procedure.

Corneal cross-linking is a process of photopolymerization of stromal collagen fibers that occurs through the combined effect of a photosensitizing agent, riboflavin, and ultraviolet light. Under UV exposure, additional covalent bonds form between collagen fibers, resulting in mechanical strengthening of the cornea at the biochemical level by approximately 300%.

In almost 100% of cases, and in 97–99% according to international data, the progression of keratoconus is halted, and as a beneficial side effect visual acuity often improves.

Why delaying treatment is risky

Many patients choose a wait-and-see strategy. However, delaying treatment carries the risk of critical corneal thinning, corneal opacities and even perforation. This can lead to severe loss of vision. At that stage, it is usually too late to offer cross-linking, and the only option to restore vision is deep lamellar or penetrating keratoplasty.

The longer you postpone treatment, the more complex it becomes and the fewer chances you have to preserve good vision.

Corneal cross-linking: is it painful and is it effective

Strictly speaking, this is more a procedure than a full-scale operation. It usually takes about 30 minutes, is painless for the patient and in 99% of cases is not associated with serious complications.

After the procedure, a bandage contact lens is placed on the eye for 3–5 days, and special eye drops are used for several weeks to speed up healing. About one month after cross-linking, patients can return to contact lens correction; in many cases, customized scleral lenses provide the highest comfort and best visual quality.

Typically, the effect of the procedure lasts 8–10 years, and if progression is documented after that time, cross-linking can be safely repeated.

Which cross-linking protocols are used in the clinic

In our clinic, we use only original, certified riboflavin solutions for the treatment of keratoconus.

Corneal collagen cross-linking in our center is performed according to two protocols: the Dresden protocol and the British-X protocol.

British-X protocol

The British-X method is a technique developed by British researchers, based on a specific standard that regulates exposure time, beam intensity and homogeneity, as well as the solutions used.

Cross-linking as the gold standard for keratoconus treatment

Today, the effectiveness of corneal cross-linking is beyond doubt. Worldwide, cross-linking is recognized as the gold standard in the treatment of keratoconus. The procedure has been performed in all developed European countries for more than 12 years.

Therefore, if you are still deciding whether to undergo cross-linking or not, do not hesitate. The earlier cross-linking is performed, the higher your chances of maintaining good vision in the long term.