Cross-linking for keratoconus (CXL): who it helps and how it works

Corneal cross-linking, or CXL, is a treatment offered when keratoconus is progressing. It works by strengthening the cornea to slow down its evolution. Its aim is not to restore sight but to stabilise the condition. Here is who it is for, how the procedure unfolds, what you can expect from it, and how it is covered.

Direct answer: what is cross-linking?

Key point. Cross-linking (CXL) is a treatment that strengthens the collagen of the cornea using vitamin B2 (riboflavin) and ultraviolet light. It is aimed at progressive keratoconus, above all in younger patients. Its purpose is to stabilise the cornea in order to slow, or even stop, the progression. It does not correct a deformation that is already established and does not replace glasses or contact lenses.

What cross-linking is, in practical terms

In keratoconus, the cornea weakens, thins and gradually deforms into a cone shape. Cross-linking sets out to reverse this mechanical fragility. The principle is to create new bridges between the collagen fibres that make up the cornea, which makes it stiffer and more resistant. This is known as collagen “cross-linking” or reticulation.

To do this, two elements are combined: riboflavin, a form of vitamin B2 applied as eye drops, and ultraviolet (UVA) light delivered in a controlled way. The riboflavin soaks into the cornea, then the UV exposure triggers the reaction that hardens the tissue. It is a medical procedure carried out under local anaesthesia with eye drops, on an outpatient basis.

Who is cross-linking for?

Cross-linking is aimed first and foremost at progressive keratoconus, that is, cases where progression is documented by corneal topography. It is intended mainly for younger patients, in whom the condition is most likely to evolve. As a rule, keratoconus that has been stable for a long time does not warrant this treatment.

• keratoconus whose progression is confirmed by repeated examinations (topography, tomography);
• a patient who is often young, in whom the cornea still has the potential to deform;
• a cornea whose thickness remains sufficient to perform the procedure safely;
• a cornea without significant opacity or overly advanced disease.

Conversely, very advanced forms, with a cornea that is too thin, too deformed or opacified, call for other options such as intracorneal rings or corneal transplantation. This is precisely the value of a full assessment: it makes it possible to establish the right indication, at the right time.

How does the procedure work?

Cross-linking is performed on an outpatient basis, without hospital admission. The eye is numbed with drops, you stay awake and are settled comfortably. The procedure generally follows these stages:

• the cornea is prepared so that the riboflavin can penetrate properly;
• the riboflavin is applied as eye drops for a set time, in order to soak into the tissue;
• the cornea is then exposed to ultraviolet light in a controlled way;
• a bandage contact lens is fitted at the end of the procedure to protect the surface and improve comfort.

There are various technical variants, which differ notably in whether or not the thin surface layer of the cornea is removed. The choice of technique rests with the surgeon, according to your cornea and the situation. The whole session generally lasts less than an hour.

What is recovery like after cross-linking?

The first few days after cross-linking call for a little patience. Discomfort, stinging, a gritty sensation and light sensitivity are common for a few days, while the surface of the cornea heals. The bandage contact lens and the prescribed treatments help you get through this stage.

• discomfort and watering during the first few days, which ease off gradually;
• vision that is often blurred at first, settling over several weeks;
• eye drops to follow scrupulously throughout the healing period;
• the instruction, more than ever, not to rub your eyes.

The return to activities is gradual and the instructions are given to you on a case-by-case basis. Vision may take time to settle, and the result is judged over time, not in the days that follow the procedure.

What results can be expected?

The aim of cross-linking is to stabilise the cornea. When it works, the progression of keratoconus slows or stops, which prevents the situation from continuing to deteriorate. This is a valuable result, because a cornea that no longer deforms remains easier to correct with glasses or contact lenses.

It is worth being clear about what CXL does not do. It does not “repair” a deformation that is already established and does not bring vision back dramatically. Some patients notice a slight improvement over the months, but that is not the goal. The success of the treatment is measured above all by the stability of the cornea over time, monitored with regular topographies.

What are the limits and precautions?

Like any medical procedure, cross-linking comes with conditions and precautions. The main limit is corneal thickness: below a certain threshold, the standard treatment cannot be carried out safely. This is one of the reasons why a precise assessment always precedes the indication.

• a minimum corneal thickness is required for the standard protocol;
• corneas that are too deformed or opacified call for other treatments;
• as after any procedure on the cornea, there is a risk of infection or delayed healing, hence the importance of following the prescribed eye drops carefully;
• certain particular situations (pregnancy, surface conditions) may lead to the procedure being postponed.

These factors are assessed with you before the procedure. The aim is not to alarm you, but to set an appropriate indication and to carry out the procedure under optimal conditions.

Is cross-linking covered?

Cross-linking is a listed procedure, carried out within the coordinated care pathway. Its coverage depends on your situation and your cover. Rather than putting forward figures, the most reliable approach is to request a detailed quote before the procedure and to check the conditions with the national health insurance scheme (Assurance maladie) and your complementary health insurance (mutuelle).

• cross-linking is part of the coordinated care pathway, on a medical indication;
• a portion may be covered by the national health insurance scheme, with the remainder often falling to the complementary health insurance;
• in certain situations, keratoconus may open up specific entitlements: to be discussed with your ophthalmologist and your insurance fund;
• always ask for a written quote to know precisely the out-of-pocket cost before making your decision.

Reimbursement conditions change and vary from one policy to another. This is why we deliberately remain cautious about figures: only a personalised quote and contact with your complementary health insurance will give you reliable information.

The pathway at the practice

The indication for cross-linking is established after an assessment at the Cachan practice: topography, measurement of corneal thickness and analysis of how the condition is progressing. If the procedure is chosen, it is arranged in a suitable specialist setting. Follow-up after the procedure then continues at the practice, with regular topographies to check that the cornea remains stable.

FAQ

Frequently asked questions about cross-linking

Sources

1. Centre de Référence National Kératocône (Pr P. Fournié, Pr D. Touboul), filière SENSGENE — Protocole National de Diagnostic et de Soins (PNDS): Kératocône. Haute Autorité de Santé, novembre 2021. has-sante.fr/jcms/p_3301044/fr/keratocone
2. American Academy of Ophthalmology (AAO) — Corneal Ectasia Preferred Practice Pattern®, 2023. aao.org/education/preferred-practice-pattern/corneal-ectasia-ppp-2023

Further reading

• Keratoconus: symptoms, causes and diagnosis
• Keratoconus: treatments and management
• Get in touch with the practice
• Glasses, contact lenses or CXL: how to choose
• Intracorneal rings or transplantation
• Progression: can it lead to blindness?

Keratoconus assessment and cross-linking indication at the Cachan practice · Tel. +33 1 45 47 08 11

In summary

Cross-linking is a reference treatment for keratoconus that is progressing. By strengthening the cornea, it sets out to slow, or even stop, the evolution of the condition. Its aim is to stabilise, not to restore sight: after CXL, most patients continue to wear a correction. The essential thing is to establish the indication early, on progressive keratoconus, after a full assessment, then to monitor the cornea over time. And before as after, the step that protects most is not rubbing your eyes.

This article has an informative and educational purpose. It is not a substitute for a medical consultation. Only an examination by an ophthalmologist can establish a diagnosis and propose management suited to your situation.