Corneal Cross-Linking (CXL) Treatment for Keratoconus

Corneal cross-linking is a treatment for keratoconus, a condition that involves weakened collagen fibers. This treatment is used to prevent keratoconus from progressing.

What Is Corneal Cross-Linking?

Corneal cross-linking (CXL) strengthens weakened collagen fibers, which are considered the cause of keratoconus. It does so by bonding, or linking, corneal fibers. 

Cross-linking can be done noninvasively or invasively. This treatment has been found to significantly prevent the disease from progressing further. 

Without this treatment, keratoconus may progress to the point where a corneal transplant is necessary.

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What Is Keratoconus?

Keratoconus is a rare condition of the cornea or front part of your eye. This condition causes the cornea to thin out and weaken over time. As it weakens, it bulges into a cone shape and distorts vision.

Medical experts at John Hopkins note that this condition typically starts in puberty and progresses into the mid-30s. Keratoconus is not common, as it affects approximately 1 in 2,000 people. 

These are symptoms of keratoconus: 

• Blurred or distorted vision 
• Increased sensitivity to light, making it difficult to drive at night
• Sudden clouding of vision 
• Frequently changing glasses prescription

If not corrected with corneal cross-linking, keratoconus may worsen. Eventually, a corneal transplant may be necessary.

If you have signs of keratoconus, see an eye doctor for diagnosis. The condition is considered chronic. 

Corneal collagen cross-linking is the primary treatment used to stop or slow down the progression of keratoconus.

What Is the Corneal Cross-Linking Procedure?

Corneal cross-linking is a special treatment that combines eye drop medication and ultraviolet light (UV) to strengthen the tissues of the cornea. It bonds the collagen fibers in the eyes to strengthen them. The bonds, or links, act like supportive beams to stabilize the cornea.

The entire procedure is relatively quick and pain-free. Your doctor first numbs your eyes and provides medication to calm your nerves. 

B2 (riboflavin) eye drops will enable the cornea to better absorb light. These drops soak into your cornea for about 30 minutes. 

As you lie back in a chair, you’ll look up at a light. The UV light combined with the eye drops trigger the development of new corneal cross-links. 

You won’t feel any pain, as your eyes will be numb. The entire treatment takes less than two hours. 

Types of Corneal Cross-Linking

The two main types of cross-linked are named for their approach to the epithelium, or outer layer of the cornea. 

• Epi-on corneal cross-linking: The epithelium is left on during the procedure. The doctor will loosen the epithelium with a sponge or eye drops before putting the B2 drops in your eye.
• Epi-off corneal cross-linking: The epithelium is removed for the procedure. After its removal, the eye drops are placed in your eyes. Since epi-off involves this removal, it is more invasive than epi-on.

According to some studies, both treatments are considered equivalent in terms of results and potential complications. 

One recent study found that epi-on treatment is preferable because it preserves the thickness of the cornea and improves visual acuity. Additionally, epi-on treatment is associated with reduced eye discomfort after surgery.

Who Is a Candidate?

If you have early signs of keratoconus, you may be a good candidate for corneal cross-linking. While CXL can slow the progression of the condition, it does not reverse cornea changes that have already happened. 

Talk with your ophthalmologist to determine if this is a treatment that is right for you.

How to Prepare for CXL

Your doctor will give you specific instructions on how to prepare for your procedure. In general, follow these tips: 

• Arrange for someone to drive you home. You won’t be able to drive following surgery.
• Do not wear eye makeup the day of the surgery.
• Bring sunglasses to protect your eyes following surgery.

Recovery After Corneal Cross-Linking for Keratoconus

Your vision may be blurry immediately following surgery. As your eyes heal, expect your vision to fluctuate somewhat. 

At times, you may have poorer vision or be more sensitive to light. Your vision should stabilize within one to three months. 

Take care with your eyes in the days following CXL. Do not rub or scratch your eyes for at least a week.

Healing times may be somewhat shorter with epi-on corneal cross-linking versus epi-off.

CXL Outcomes

Corneal cross-linking is designed to slow your disease and prevent further vision problems. In some cases, patients find that their vision improves over time. 

Due to these vision changes, you may need to get new contacts or glasses. 

Risks of Corneal Cross-Linking

Like any surgery, there are risks associated with CXL. These are the most common:

• Infection
• Severe swelling
• Pain
• Corneal damage
• Issues with epithelium healing
• Persistent vision issues

Ask your doctor about potential risks specific to your age, medical status, and any previous conditions.

Overall, CXL is considered a low-risk procedure.

Alternatives to CXL

An alternative treatment for keratoconus is the use of Intacs. The FDA approved Intacs as an alternate treatment to corneal cross-linking or a corneal transplant.

Intacs are corneal implants. They involve surgery to place small, clear plastic arcs into the cornea. They work to reconfigure the cornea to its original curvature. 

Intacs flatten the bulged, or domed, part of the cornea, helping to correct blurred vision caused by keratoconus. The quick procedure is performed on an outpatient basis.

While Intacs can greatly improve vision that has been damaged by keratoconus, it cannot stop the progression of the condition. As a result, a combined approach of CXL and Intacs may be recommended.

Corneal Cross-Linking FAQs 

What does corneal cross-linking do?

Corneal cross-linking stops progressive keratoconus from worsening. It can prevent vision loss and further weakening of the eyes. It also may help you avoid major surgery, such as a corneal transplant.

What happens after corneal cross-linking?

Corneal cross-linking helps to make the tissues of your cornea stronger. After surgery, your cornea may flatten, helping to protect or even improve your vision. 

How painful is corneal cross-linking?

Corneal cross-linking is considered a painless procedure. Your eyes will be numb, and you should not experience any pain during surgery.

How should I care for my eyes after CXL?

Though you won’t experience pain during CXL, you may have some discomfort during the healing process. Expect your eyes to be sore for about five days. 

Do not rub your eyes during this time. Wear sunglasses as you might experience light sensitivity. You can usually resume normal activities after about a week.

References

1. Corneal Cross-Linking: Current USA Status: Report From the Cornea Society. (October 2018). Cornea.

2. Updates on Managements for Keratoconus. (June 2018). Journal of Current Ophthalmology.

3. Keratoconus. John Hopkins Medicine.

4. Collagen Cross-Linking: Strengthening the Unstable Cornea. (December 2008). Clinical Ophthalmology.

5. About Corneal Transplants. American Academy of Ophthalmology (AAO).

6. Epi-Off Versus Epi-On Corneal Collagen Cross-Linking in Keratoconus Patients: A Comparative Study through 2-Year Follow-Up. (July 2018). Journal of Ophthalmology.

7. Intacs or Intracorneal Ring Segments (ICRS). Kellogg Eye Center, University of Michigan.

8. Epi-On Cross-Linking May Speed Visual Recovery. (October 2019). Optometry Times.

9. Corneal Cross-Linking (Collagen Cross-Linking). Kellogg Eye Center, University of Michigan.

10. Examining the Cross-linking/Intacs Link. (November 2012). Review of Ophthalmology.

11. Your Top 12 Crosslinking Questions—Answered! (January 2018). Review of Ophthalmology.

12. Keratoconus Managed With Intacs One-Year Results. (October 2005). JAMA Ophthalmology.