Collagen Cross-Linking

What is CXL?

Corneal collagen cross-linking is a technique that was first used in 1998 to treat patients with a disease called keratoconus. In keratoconus, the cornea (the front clear window of the eye) becomes weak, thin, and irregularly shaped. Keratoconus affects about 1 in 750 adults in the US population, typically starting in the late teens or early 20s. CXL is now being performed for patients with this condition in approximately 200 centers throughout the world, including roughly 25 centers in the US. Through a research study, Dr. Wallace and the team at LA Sight is now able to provide this investigational treatment to our patients using this technology. Other terms that have been used to describe this treatment include “UV Cross-Linking,” “corneal strengthening,” “corneal cross-linking with riboflavin,” and “C3R” (for Corneal Collagen Cross-Linking with Riboflavin).

Normal cornea compared to a Keraoconus cornea

What does CXL do?

Corneal collagen cross-linking strengthens the cornea by allowing it to re-form new crosslinks between the collagen fibers. These new crosslinks help strengthen the cornea which stops the thinning process and further loss of vision.

Example of Crossbeams, similar to the concept Cross Linking fibers in CXL
CXL works by adding “crossbeams” between
the weak layers of the cornea in keratoconus eyes

How effective is CXL?

Many research studies have shown that CXL prevents further vision loss in over 95% of patients, with 60-70% of patients having improved vision.1,2,3,4,5

How long does CXL treatment last?

Based on CXL study results of over more than a decade, the beneficial effects of CXL appear to last for a long time and there is evidence that this strengthening effect will be permanent 2.

Is CXL new?

Corneal collagen cross-linking has been performed since 1998. The results and safety profile of CXL have been excellent in numerous studies throughout the world1 . The CXL procedure is now routinely performed on patients as young as 10 years old in Europe to prevent the development of keratoconus.

What is keratoconus?

Keratoconus is a common disease which occurs in between 1 in 500 and 1 in 1000 Americans. In this condition, the cornea becomes weak, progressively thins, and becomes irregular in shape producing high levels of astigmatism. This can interfere with the ability to see clearly. Often keratoconus patients first require glasses, then contact lenses, and if the condition progresses to a severe level, a corneal transplant may be required.

Can CXL prevent the need for corneal transplant?

Many studies have shown that CXL can often prevent the need for a corneal transplant and allow patients to wear contact lenses or glasses more comfortably and safely again1,2,3,4,5.

Is CXL like LASIK?

No. LASIK is a procedure that reduces or, in some cases, may even eliminate the need for glasses or contact lenses by removing corneal tissue. The CXL treatment does not remove tissue. The purpose of CXL is to prevent further deterioration of vision for most patients and to potentially improve vision. Patients will typically require a lower eyeglass prescription and can have an easier time being fit with contact lenses.

Can a corneal transplant be done after CXL?

If CXL does not prevent the need for a corneal transplant, then a corneal transplant can generally be performed.

Does CXL need to be repeated?

In many studies, the vast majority of patients respond to a single CXL treatment and do not need to have the procedure repeated. For the occasional patient in whom this treatment is not successful, CXL can often be repeated.

Does insurance cover CXL treatment?

Unfortunately, we have yet to see an insurance policy that does cover this treatment.

Is financing available?

Convenient, affordable financing is available to help our patients get the treatment they need before their keratoconus or other similar condition progresses to the point where they can no longer have CXL.

Can CXL be performed for everyone with keratoconus?

To qualify for the CXL study, patients must be at least 18 years old and their corneas cannot be too thinned or too scarred for the procedure. During your consultation, we will determine if CXL might be a good treatment option. Washington Eye Physicians and Surgeons offers a complimentary, five minute no-touch, screening test to determine whether CXL can potentially be of benefit.

Should your relatives be tested?

As you may know, keratoconus is a condition that often runs in families, so it’s important to arrange a screening for all family members of patients with keratoconus. If caught early, there is a good chance that CXL can halt the progression of keratoconus and prevent the need for a corneal transplant and/ or uncomfortable contact lens wear for many patients.

How is CXL performed?

The CXL treatment is an outpatient procedure performed in the doctor’s office. You recline in a chair with the back tilted down. Vitamin B2 (riboflavin) eye drops are instilled in the eye every until the corneal is adequately saturated – about 40 – 50 minutes. Once ‘loaded’ the corneas are exposed to a special UV light source for half an hour; the UV light causes the Riboflavin to effect the cross-linking of collagen. This treatment approach is called “trans-epithelial” cross-linking as the surface lining cells are retained, not removed, in the treatment process.6

How long does the whole procedure take?

If two eyes are being treated at once, the procedure takes approximately an hour and a half. If only one eye is being treated at a time, the procedure takes approximately one hour.

Does the CXL procedure hurt?

No. Anesthetic eye drops are used to avoid any discomfort during the procedure.

What are the potential risks?

Although this procedure has been used for more than 10 years, there may still be some risks or side-effects that are not known yet. The most common side effects of epithelial (outer layer of the eye) removal include moderate pain, and blurred vision that typically lasts up to 5 days. There is also risk of infection, corneal inflammation, corneal haze, dry eye, and delays in epithelial healing.

The most common side effects from using riboflavin drops are blurred vision, and mild redness or stinging in your eyes. Uncommon side effects can include difficulty breathing, wheezing, a sudden drop in blood pressure, a fast pulse, sweating, or swelling around the mouth, throat, or eyes. The most common side effects of the UV-X light source include blurred vision, mild redness or stinging in the eyes. Another side effect of the UV-X light source is if too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged. This can lead to temporary loss of vision for 24-48 hours. It may also lead to additional surgery.

An uncommon side effect may be changes to other layers of your cornea. The most common side effects of topical antibiotics include: ocular irritation (pain, swelling, burning, dry, or itchiness of the eye). There may be side effects or discomforts from the medications that are not yet known. Although rare, a serious infection or inflammation can lead to permanent loss of vision, or even loss of the eye. Additional surgery may rarely be needed.

Can I have one eye treated at a time?

Yes, your doctor will discuss with you the advantages and disadvantages of treating one eye or two eyes at a time.

Can I have CXL if I already had a corneal transplant?

Each patient and each patient’s eyes are different. In some cases CXL can be performed after corneal transplantation.

If CXL works for me and stops my vision from getting worse, can I have laser vision correction afterwards?

Some patients may be able to have an excimer laser treatment (PRK) to improve their vision without glasses after they have healed from the CXL procedure.

Do I have to stop wearing contacts before having CXL?

If you wear soft contact lenses it is recommended that you do not wear these lenses for about 3 days before the procedure. Patients wearing hard or combination lenses such as SoftPerm or soft toric contacts are recommended to be out of their lenses for approximately 10 days prior to the CXL procedure.

When can I resume wearing contact lenses?

Most patients can return to wearing contact lenses 1 to 2 weeks after having the cross-linking procedure.

Will I need new glasses or contacts after CXL?

Because cross-linking often improves vision, patients usually find that their old contacts or glasses may no longer work and they need to be refit with new, glasses and/or contact lenses.

When will I notice any improvement in my vision after CXL?

Most patients find that for the first few days after the cross-linking treatment, their vision is actually worse than it was before the procedure. This usually goes on for roughly 2-4 weeks. Many patients start to notice positive effects 2-3 weeks after the procedure and major improvement in vision generally takes 4-6 months. In some studies, five years after cross-linking, patient’s vision and astigmatism are still continuing to improve2.

What is astigmatism?

Astigmatism simply means that the front surface of the eye (the cornea or clear window in front of the eye) is shaped more like a football than like a basketball.

What do ladders and Keratoconus have in common?

In keratoconus, the cornea has weakened structural support; fewer cross-links or support beams. This weakened structure allows the cornea to bulge outwards. The cross-linking procedure adds ladder rungs or cross-links to the cornea, making it more stable.

For more information about keratoconus, and/or our diagnostic screenings and treatments, please call LA Sight and ask to speak with a CXL coordinator or visit the website of the CXL-USA Study Group. You may also download a pdf of the recent article publsihed by the CXL-USA study group, Answering Patient’s Questions About Cross-Linking.


1. Wollensak G, Spoerl E, Seiler T.; Riboflavin/ultraviolet-a-induced collagen cross-linking for the treatment of keratoconus. AJO 2003 May;135(5):620-7

2. Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat LE.; Collagen cross-linking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg. 2008 May;34(5):796-801.

3. Coskunseven E, Jankov MR 2nd, Hafezi F.; Contralateral eye study of corneal collagen cross-linking with riboflavin and UVA irradiation in patients with keratoconus.

J Refract Surg. 2009 Apr;25(4):371-376

4. Grewal DS, Brar GS, Jain R, Sood V, Singla M, Grewal SP.; Corneal collagen cross-linking using riboflavin and ultraviolet-A light for keratoconus: one-year analysis using Scheimpflug imaging. J Cataract Refract Surg. 2009 Mar;35(3):425-32.

5. Spoerl E, Mrochen M, Sliney D, Trokel S, Seiler T.; Safety of UVA-riboflavin cross-linking of the cornea. Cornea. 2007 May;26(4):385-9.

6. Trattler W, Rubinfeld R, Corneal Collagen Cross-linking; Cataract and Refractive Surgery Today; September 2009