Corneal Cross-Linking

What is Corneal Cross-Linking?

Corneal cross-linking is a surgical procedure that treats a thinning or bulging cornea (transparent outer layer of the eye). A breakdown in collagen fibers (proteins holding the cornea together) typically causes this.

Collagen fibers are "cross-linked" during surgery to strengthen and support the cornea's structure. 

Disease or complications from various eye surgeries can lead to a breakdown in corneal collagen fibers and cause corneal ectasia (eye conditions that cause cornea thinning and bulging).

Corneal ectasia can result in vision changes that glasses or contact lenses cannot usually correct. These vision changes include:

• Blurred or distorted vision  
• Squinting to see
• Myopia (nearsightedness)
• Astigmatism
• Shadows or ghost images
• Decline in visual acuity (distance vision)

Corneal collagen cross linking treats the following types of corneal ectasia:

• Keratoconus, which is when the cornea slowly develops a cone shape 
• Post-LASIK ectasia, a rare complication of LASIK surgery that weakens corneal tissue and causes bulging

Who is a Candidate for Corneal Cross-Linking?

People who have a thinning, cone-shaped, or bulging cornea are candidates for cross linking surgery.

An optometrist or ophthalmologist will consider several factors before recommending cross linking surgery, including:

• Progression or worsening of disease
• Age
• Corneal thickness
• If glasses or contact lenses can correct the condition

Corneal cross-linking is recommended for people whose disease or condition is worsening and if glasses or contact lenses cannot correct it. 

Surgery will not work if the cornea is too thin or the central corneal stroma (supporting layer of tissue) is surgically removed. 

Corneal Cross-Linking Procedure

Corneal cross-linking surgery is a minimally invasive procedure done in an outpatient setting. The surgery takes about an hour, and you should ask someone to drive you home afterwards. 

The procedure uses a combination of ultraviolet light and vitamin B eye drops to strengthen corneal collagen fibers and reduce cornea bulging.

Before Surgery

To prepare for cross linking surgery, you should follow instructions from your eye doctor, such as:

• Don't wear makeup, perfume, or aftershave the day of the procedure 
• Don’t eat a heavy meal
• Dress comfortably 
• Ask someone to drive you home

During Surgery

Your doctor will numb your eye(s) with anesthetic eye drops and administer a mild sedative. You’ll remain awake throughout the entire procedure. 

The doctor will have you lie flat on your back and continue with surgery. First, they will remove the corneal epithelium (outer layer of the cornea). Next, they will administer riboflavin eye drops (vitamin B) onto the cornea and wait 30 minutes for the drops to absorb.

Then, they will shine a UV light ray on the cornea for 30 minutes. During this time, the light stimulates the riboflavin, resulting in strong collagen bonds.

Finally, they will apply a bandage contact lens over the cornea to promote healing.

After Surgery

After surgery, your doctor will schedule a follow-up appointment, usually for the next day. You will need to wear the bandage lens about a week after the procedure. You might have blurry and distorted vision after the procedure.

To promote healing and minimize infection, your doctor may give you medicated eye drops to administer daily. After surgery, you should also avoid:

• Rubbing or touching your eyes
• Getting water in your eyes
• Wearing makeup
• Strenuous exercise and heaving lifting
• Dust and smoke
• Flying or swimming for a month

Most people can resume normal activities 1 to 2 weeks after a cross linking procedure. 

Side Effects of Corneal Cross-Linking

Common side effects after corneal cross-linking include:

• Foreign body sensation (feeling like something is in your eye)
• Light sensitivity (wear sunglasses to reduce this side effect)
• Dry eyes
• Discomfort
• Mild eye pain
• Blurry vision 

If you have severe or worsening eye pain or a sudden vision change, call your eye doctor immediately. 

You might need to get a new prescription for contact lenses and eyeglasses 6 to 8 weeks after corneal cross-linking surgery.

What are the Risks?

Although rare, corneal cross-linking can be associated with adverse side effects and risks, including:

• Infection
• Vision loss
• Scarring
• Worsening of corneal thinning and bulging
• Corneal striae (white lines in your cornea)
• Severe inflammation 

Corneal Cross-Linking Outlook & Success Rates

Corneal cross-linking was FDA-approved in 2016 to treat progressive keratoconus (cone-shaped cornea) and post-LASIK ectasia (bulging cornea). It has also been an approved treatment in Europe for many years.

Corneal cross-linking effectively treats keratoconus. Ninety percent of people have stable eyes 10 years after corneal cross-linking surgery.⁹

Alternative Treatments

Currently, cross linking is the only treatment that can stop progressive keratoconus.

For people with keratoconus that is stable and not getting worse, there are alternative treatments to cross linking, including:

• Rigid or hard contact lenses. These lenses adhere to the cornea’s shape and improve vision.
• Hybrid contact lenses. Like rigid lenses, these contacts improve vision but are comfortable like a soft lens.
• Scleral lenses. These lenses fit almost any size cornea and provide good vision. 
• Corneal transplant. This procedure is necessary when contact lenses and cross linking are not an option. 

Summary

Corneal collagen cross linking is FDA-approved to treat progressing keratoconus (cone-shaped cornea) and post-LASIK ectasia. 

Corneal cross-linking treats a thinning and bulging cornea caused by weakened collagen fibers. The procedure combines vitamin B eye drops with UV light to strengthen collagen fibers and stimulate a normal cornea shape.

The cross linking procedure takes about one hour and occurs in an outpatient setting. The procedure is not painful, your eyes will be numbed with eye drops, and you may be given a mild sedative. Recovery takes about one to two weeks.