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What is Corneal Crosslinking? Strengthening the cornea in a targeted manner

Illustration: cross-section of the eye showing the cornea, lens, retina and optic nerve

In brief

What is crosslinking?

Crosslinking (CXL, corneal cross-linking) is a treatment that uses riboflavin drops and UVA light to stiffen the cornea and thus halt progressive keratoconus. At EyeLaser Zürich, Dr. Victor Derhartunian has been performing crosslinking since 2007. For progressive keratoconus, basic health insurance pays; for self-payers it costs CHF 2’300 per eye.

Crosslinking at a glance — EyeLaser Zürich
Method Riboflavin (vitamin B2) and UVA light cross-link the collagen fibers of the cornea
Device C-EYE (UVA source from Switzerland)
Suitable for documented progressive keratoconus, PMD or ectasia after LASIK; in children often already at diagnosis
Not suitable for deep central scars, acute infection, pregnancy (postponed)
Duration around one hour per eye, one eye per appointment
Unable to work usually 5 to 7 days (office work)
Effect halts progression in around 92 to over 98 out of 100 eyes (Koller et al. 2009; Raiskup-Wolf et al. 2008); usually does not make vision sharper
Surgeon Dr. Victor Derhartunian personally
Costs basic health insurance for progressive keratoconus (KLV Annex 1); self-payers CHF 2’300 per eye
Medically reviewed by Dr. med. univ. Victor Derhartunian, FEBO, FWCRS on 2 October 2026 · Last updated on 2 October 2026

Crosslinking is part of the step-by-step keratoconus treatment: first stabilize, then improve vision.

More than just a procedure: A strategic treatment

Patient lying under the operating microscope while the surgeon in cap and mask leans over her

At our clinic, crosslinking is not an isolated procedure but part of an individual, strategic treatment plan. While CXL takes over the biochemical stabilization, it can be useful in some cases to first mechanically stabilize and shape the cornea.

In advanced cases, we may therefore first implant biological ring segments (CAIRS). These immediately strengthen the cornea and improve its shape. Only in a second, later step do we then perform crosslinking – often combined with a surface-smoothing laser treatment – to finally secure the result.

What is corneal crosslinking?

Can crosslinking prevent a corneal transplant?

Hand pointing to the lens in an anatomical eye model, with an enlarged lens model beside it

Often, yes. A corneal transplant is a major procedure with a long healing period and a risk of rejection. Crosslinking intervenes earlier: it stiffens your own cornea before it becomes too thin and too severely deformed. In a long-term study from Dresden, the cornea remained stable after ten years, the bulging had even decreased slightly, and the authors saw a reduced need for transplants (Raiskup et al. 2015). If the deformation is already severe, CAIRS can additionally flatten the cornea.

The treatment process: Your day at EyeLaser Zurich

We have designed the entire process to be as comfortable and stress-free as possible for you.

Arrival & Preparation

You will be received in our clinic. Your eye will be prepared with numbing drops so that you feel nothing during the entire procedure.

The intervention

You lie comfortably on a couch. Depending on the procedure, the epithelium is removed, and the riboflavin drops are applied over a period of approx. 20-30 minutes.

The irradiation

You then look into the UVA light; depending on the protocol, this takes 10 to 30 minutes. We decide which protocol is suitable after the tomography. Your position is continuously monitored throughout.

Conclusion

After the irradiation, a protective bandage contact lens is placed on your eye. This remains there for a few days to support healing.

What types of crosslinking are there?

Crosslinking, cross-linking or CXL all refer to the same procedure. There are several protocols; which one we choose depends on corneal thickness, age and findings.

Crosslinking variants compared
Variant What is different When Evidence
Standard (epi-off, Dresden protocol) the top cell layer is removed, 30 minutes of low-intensity UVA basic form, studied the longest long-term data over ten years (Wollensak et al. 2003; Raiskup et al. 2015)
Accelerated crosslinking higher UV intensity, shorter irradiation frequently used in everyday practice according to a meta-analysis of six randomized studies, halts progression similarly to the standard (Kobashi and Tsubota 2020)
Epi-on (transepithelial) the cell layer is preserved or only loosened selected cases, less discomfort in the first few days less well documented than epi-off
Thin cornea: hypo-osmolar riboflavin special drops make the cornea swell before irradiation cornea thinner than 400 µm Hafezi et al. 2009
Thin cornea: Sub400 the UV dose is individually adjusted to the thickness very thin cornea 35 of 39 eyes stable after one year (Hafezi et al. 2021)

At EyeLaser Zürich, we decide which variant is suitable in each individual case after the tomography.

Who performs crosslinking in Zurich?

Dr. Victor Derhartunian

At EyeLaser Zürich, Dr. med. univ. Victor Derhartunian, FEBO, FWCRS, performs every crosslinking procedure personally. He has been using the procedure since 2007 and was one of the first users in Europe after its CE approval.

“When I started crosslinking at the University Eye Hospital Frankfurt in 2007, it was a new method. Later, at IROC in Zurich, I worked with Professor Theo Seiler, one of the developers of the procedure. This experience goes into every treatment.” — Dr. Victor Derhartunian

How well does crosslinking work, and what are the risks?

Close-up of a grey-blue eye with superimposed digital measuring circles

Results from studies

In a randomized study with 100 eyes, the cornea became somewhat flatter on average over three years after crosslinking, while without treatment it continued to steepen (Wittig-Silva et al. 2014). In a Zurich study with 117 eyes, keratoconus continued to progress in 7.6 % after one year (Koller et al. 2009). These are not our own figures.

Close-up of a blue eye with one half of the iris coloured lighter

Risks and how often they occur

  • Further progression: 7.6 %; crosslinking can be repeated
  • Sterile inflammatory infiltrates: 7.6 %, treatable with drops
  • Loss of two or more lines of visual acuity: 2.9 %, more frequent from age 35
  • Scar in the center of the cornea: 2.8 %
  • Infection, delayed healing: no reliable frequency data

Source: Koller et al. 2009, 117 eyes, one year.

Woman holding her glasses out at arm’s length, her face blurred behind them

Then improve vision

After stabilization, vision can often be improved: improving vision with keratoconus with topography-guided Trans-PRK, CAIRS or ICL.

Close-up of a grey-blue eye with superimposed digital measuring circles

Results from studies

In a randomized study with 100 eyes, the cornea became somewhat flatter on average over three years after crosslinking, while without treatment it continued to steepen (Wittig-Silva et al. 2014). In a Zurich study with 117 eyes, keratoconus continued to progress in 7.6 % after one year (Koller et al. 2009). These are not our own figures.

Close-up of a blue eye with one half of the iris coloured lighter

Risks and how often they occur

  • Further progression: 7.6 %; crosslinking can be repeated
  • Sterile inflammatory infiltrates: 7.6 %, treatable with drops
  • Loss of two or more lines of visual acuity: 2.9 %, more frequent from age 35
  • Scar in the center of the cornea: 2.8 %
  • Infection, delayed healing: no reliable frequency data

Source: Koller et al. 2009, 117 eyes, one year.

Woman holding her glasses out at arm’s length, her face blurred behind them

Then improve vision

After stabilization, vision can often be improved: improving vision with keratoconus with topography-guided Trans-PRK, CAIRS or ICL.

How much does crosslinking cost, and does health insurance pay?

Smiling older man with a white beard at an eye examination, a doctor in a white coat in front of him

In Switzerland, crosslinking for advancing (progressive) keratoconus is a mandatory benefit of basic health insurance (KLV Annex 1); the deductible and co-payment apply as usual. The prerequisite is that progression is documented by measurements. We recommend obtaining cost approval from your health insurer before the procedure; our team compiles the findings for this.

  • Self-payers: CHF 2’300 per eye, fixed price including the follow-up checks in the first three months
  • Pre-examination with corneal tomography: if medically indicated, via health insurance under TARDOC; for self-payers CHF 300, credited if you have treatment
  • Crosslinking with PTK: CHF 2’300 plus PTK CHF 1’500 per eye (always self-pay)
  • Separate: medication and eye drops on prescription from the pharmacy

All prices: costs for keratoconus.

Do I need crosslinking?

A comparison of two corneal measurements will show this. Book an examination at Strehlgasse 33 in Zurich and bring any previous measurements with you.

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FAQ: Frequently asked questions about crosslinking in Zurich

What exactly does crosslinking do for my keratoconus?

Crosslinking strengthens the cornea: riboflavin drops and UVA light form new connections between the collagen fibers, and the tissue becomes stiffer. In studies, this halts progressive keratoconus in around 92 to over 98 out of 100 eyes (Koller et al. 2009; Raiskup-Wolf et al. 2008). At EyeLaser Zürich, Dr. Victor Derhartunian has been performing crosslinking since 2007.

Is the result of crosslinking permanent?

Usually, yes. In a Dresden study with 34 eyes, the cornea remained stable ten years after crosslinking, and the bulging had even decreased on average (Raiskup et al. 2015). In some eyes, keratoconus nevertheless continues to progress; crosslinking can then be repeated. That is why, at EyeLaser Zürich, we also check the cornea regularly after treatment.

Will I be able to see better with crosslinking?

The primary and most important goal of crosslinking is to stop the progression of keratoconus, not to improve vision. In some patients, a slight flattening of the cornea and thus a slight improvement in vision occurs as a positive side effect. However, you should not rely on this. A targeted improvement in vision is achieved through other, subsequent procedures.

 

Do I have to be treated immediately after diagnosis?

Not necessarily. Treatment is necessary when a clear progression – i.e. a deterioration – of keratoconus is proven. This is exactly why we use our high-precision diagnostics with the MS-39 to objectively measure changes and determine the right time. In children and adolescents, we often do not wait, because keratoconus frequently progresses rapidly at this age (Chatzis and Hafezi 2012).

 

Is the crosslinking treatment painful?

During the procedure, you usually feel no pain thanks to numbing eye drops. However, we often hear this concern. Honestly, the first 1-3 days after the procedure (especially with the epi-off procedure) are uncomfortable. You may experience pain, a foreign body sensation and severe light sensitivity. However, we will give you effective painkillers and an exact eye drop schedule to get you through this phase well.

 

How long will I be unable to work after crosslinking?

Plan for a downtime of about one week. During this time, the top layer of the cornea (the epithelium) heals. For office work, you can usually return to work after 5-7 days. You should avoid physically strenuous or dirty work for at least two weeks.

 

When can I drive again after the procedure?

Your vision will fluctuate in the first few weeks after the procedure. You may not drive again until you feel absolutely safe and the legally required visual acuity has been stably achieved again. This can take several weeks and will be checked during the follow-up checks.

 

When can I exercise or go swimming again?

Light sporting activities such as jogging or the gym are usually possible again after 1-2 weeks. You should refrain from visiting swimming pools, saunas and steam baths, as well as from contact sports, for at least one month to protect against infection.

 

How much does a crosslinking treatment cost in Switzerland?

For progressive keratoconus, basic health insurance pays for crosslinking (KLV Annex 1); the deductible and co-payment apply. For self-payers, crosslinking at EyeLaser Zürich costs CHF 2’300 per eye. You receive medication and eye drops on prescription from the pharmacy. We recommend obtaining cost approval beforehand and compile the documents for you.

Will my health insurance (basic health insurance) cover the costs of crosslinking?

Yes. In Switzerland, crosslinking for demonstrably progressive keratoconus is on the list of mandatory benefits of basic health insurance (KLV Annex 1). Progression must be documented by measurements. EyeLaser Zürich recommends obtaining cost approval before the procedure and supports you with this; you pay the deductible and co-payment as with any treatment.

My cornea is very thin. Can I still be treated?

Often, yes. The former lower limit of 400 micrometers no longer applies absolutely. There are two options: special riboflavin drops make the cornea swell before irradiation (Hafezi et al. 2009), or the UV dose is adjusted to the thickness with the Sub400 protocol; with this, 35 of 39 eyes were stable after one year (Hafezi et al. 2021). EyeLaser Zürich decides which option is suitable after the tomography.

Can both eyes be treated at the same time?

For safety reasons and to make your recovery phase as comfortable as possible, we usually treat the eyes at separate appointments. The interval between treatments is usually one to four weeks.

 

What are the risks of crosslinking?

The main risks after crosslinking are further progression (7.6 % after one year), sterile inflammatory infiltrates (7.6 %), a loss of two or more lines of visual acuity (2.9 %) and a scar in the center of the cornea (2.8 %), according to a Zurich study with 117 eyes (Koller et al. 2009). Infections are rare. At EyeLaser Zürich, we discuss your personal risk before the procedure.

Can crosslinking be combined with laser treatment?

Yes, that is one of our great strengths. The laser (topo-guided Trans-PRK/PTK) can be combined directly with crosslinking to stabilize the cornea and smooth its surface at the same time. This can significantly improve the quality of vision.

 

What is the treatment process for keratoconus at EyeLaser Zürich?

First, we measure the cornea with the MS-39 and compare the results with earlier measurements. If the keratoconus is progressing, Dr. Victor Derhartunian performs crosslinking, one eye per appointment. Check-ups follow; once the cornea is stable, we discuss at EyeLaser Zürich whether CAIRS, a laser or an ICL can improve your vision.

Is crosslinking possible for children and adolescents?

Yes. In a Zurich study with 59 eyes of 9- to 19-year-olds, keratoconus progressed in 88 %; crosslinking proved to be safe, and the authors recommend not waiting for progression to be documented (Chatzis and Hafezi 2012). That is why, at EyeLaser Zürich, we discuss crosslinking with parents early on.

Does crosslinking also help with PMD or ectasia after LASIK?

Yes, crosslinking is also used for pellucid marginal degeneration (PMD) and for ectasia after LASIK if the cornea is becoming progressively weaker. Whether basic health insurance pays in these cases is clarified by EyeLaser Zürich with a cost approval request, because the KLV explicitly names progressive keratoconus. For self-payers, crosslinking costs CHF 2’300 per eye.

Sources
  1. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-A-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol 2003;135:620–627. PubMed 12719068
  2. Koller T, Mrochen M, Seiler T. Complication and failure rates after corneal crosslinking. J Cataract Refract Surg 2009;35:1358–1362. PubMed 19631120
  3. Raiskup-Wolf F, Hoyer A, Spoerl E et al. Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg 2008;34:796–801. PubMed 18471635
  4. Raiskup F, Theuring A, Pillunat LE, Spoerl E. Corneal collagen crosslinking with riboflavin and ultraviolet-A light in progressive keratoconus: ten-year results. J Cataract Refract Surg 2015;41:41–46. PubMed 25532633
  5. Wittig-Silva C, Chan E, Islam FM et al. A randomized, controlled trial of corneal collagen cross-linking in progressive keratoconus: three-year results. Ophthalmology 2014;121:812–821. PubMed 24393351
  6. Kobashi H, Tsubota K. Accelerated Versus Standard Corneal Cross-Linking for Progressive Keratoconus: A Meta-Analysis of Randomized Controlled Trials. Cornea 2020;39:172–180. PubMed 31369463
  7. Hafezi F, Mrochen M, Iseli HP, Seiler T. Collagen crosslinking with ultraviolet-A and hypoosmolar riboflavin solution in thin corneas. J Cataract Refract Surg 2009;35:621–624. PubMed 19304080
  8. Hafezi F, Kling S, Gilardoni F et al. Individualized Corneal Cross-linking With Riboflavin and UV-A in Ultrathin Corneas: The Sub400 Protocol. Am J Ophthalmol 2021;224:133–142. PubMed 33340508
  9. Chatzis N, Hafezi F. Progression of keratoconus and efficacy of pediatric corneal collagen cross-linking in children and adolescents. J Refract Surg 2012;28:753–758. PubMed 23347367
  10. Federal Office of Public Health (FOPH). KLV Annex 1, edition of 1 July 2026, section 6 Ophthalmology: “UV crosslinking of the cornea for progressive keratoconus (CXL)”.