Keratoconus · Treatments

Corneal
cross-linking

Cross-linking is a procedure intended to reinforce the cornea so as to prevent keratoconus from continuing to distort. It is for forms whose progression has been documented by examinations compared over time. It is not surgery to correct sight: the decision to offer it follows from an indication established beforehand.

Treating keratoconus →

What it does, and what it does not do

Cross-linking aims to halt progression, not to correct vision. After the procedure you will still need glasses or lenses, and your correction will remain broadly of the same order. The objective is that the cornea should stop distorting, so as to avoid reaching the stages where the options become heavier.

Slight flattening of the cornea is sometimes observed over time. This is a possible effect, not the objective pursued: it should not be expected, nor built into the correction plan.

The principle

The cornea owes its strength to collagen fibres linked to one another. In keratoconus these links are insufficient, and the cornea gives way progressively under the internal pressure of the eye and the shearing forces of eye rubbing.

Cross-linking consists in creating additional links between these fibres. It combines two elements: riboflavin, a molecule close to vitamin B2, applied as drops to permeate the thickness of the cornea, and low-intensity ultraviolet light, which triggers the reaction. The result sought is a mechanically more resistant cornea.

When it is considered

The central criterion is documented progression, not the severity recorded.

Progression and monitoring →

Several conditions are checked before the indication is retained:

sufficient corneal thickness, the minimum thickness governing the safety of the treatment;
the absence of significant central opacity;
the absence of uncontrolled surface disease, in particular inflammation or marked dryness;
an expected normal corneal healing.

Age weighs on the decision. In adolescents and young adults, progression is on average more rapid and the threshold for intervening shifts accordingly.

How the procedure is carried out

Cross-linking is performed as a day case, under local anaesthesia with drops. The eye is held open by a lid speculum; you do not have to control your blinking.

The procedure has two stages: saturation of the cornea with riboflavin, then exposure to ultraviolet light. The whole takes of the order of an hour, a substantial part of which is waiting.

Two families of protocol coexist. In the first, the epithelium — the thin surface layer — is removed before saturation. These are the protocols that have shown the best efficacy to date. In the second, the epithelium is preserved. Removing it eases the penetration of riboflavin but makes the immediate recovery more uncomfortable; preserving it is better tolerated but saturation is less direct. The choice is discussed according to the thickness of your cornea and the clinical context.

A bandage contact lens is usually placed at the end of the procedure when the epithelium has been removed, to improve postoperative comfort appreciably.

Recovery

You should be prepared: the first days are uncomfortable when the epithelium has been removed.

The first two to four days: pain, watering, light sensitivity, while the epithelium re-forms. Painkillers are prescribed alongside the bandage lens.
The first weeks: blurred and fluctuating vision, sometimes more so than before the procedure. This is usual and transient.
The following months: vision settles. Several months are needed before refitting a correction, and longer still before refitting lenses.

Eye drops are prescribed for several weeks, and check-ups are close together at the start.

Said plainly

The limits and the risks

Like any procedure, cross-linking carries risks, which remain uncommon but must be known:

a transient clouding of the cornea known as haze, usually reversible, sometimes persistent;
a delay in healing of the epithelium;
an infection, rare but possible;
a drop in corrected vision, uncommon.

When stabilisation is not achieved. The procedure does not halt progression in every patient. Progression may be found later, and a further treatment discussed. This is one of the reasons why monitoring continues after the procedure.

The available studies report stabilisation in the majority of cases, with what is now substantial follow-up. These data describe series of patients and do not predict an individual result.

After the procedure

Follow-up continues indefinitely, at a rhythm that spaces out as stability is confirmed. The optical correction is reassessed later, and lens fitting resumed when the surface allows.

Cross-linking dispenses neither with correction, nor with monitoring, nor with the precautions concerning eye rubbing.

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