Cross-Linking Eye Surgery for Keratoconus

Saima Andrabi   by Saima Andrabi, MS, Clinical Biochemistry    Last updated on February 10, 2020,

Our eyes can see through the cornea (outer lens or windshield of the eye). Normally the cornea has a round ball-like shape. However, in some conditions, the round dome shape of cornea gets changed which results in the bulging of cornea outward and downward like a cone. Such a condition is called keratoconus.

Keratoconus occurs when collagen fibers of the eye become weak and are unable to hold up the normal round shape of the cornea. As a result, the cornea becomes cone-shaped and bulges outwards.

What is Cross-Linking Eye Surgery? How is it Performed?

Corneal cross-linking (CXL) procedure is used for treating patients suffering from an eye disease called keratoconus. Keratoconus makes the tissues in the eyes weak due to which the cornea loses its original round shape.

Cross-linking eye surgery is a relatively non-invasive medical procedure that is used for strengthening and stabilizing the corneal tissues. As a result, the cornea becomes stable and is prevented from bulging more.

Corneal cross-linking surgery prevents the progressive keratoconus from getting worse and also substitutes the need for corneal transplant surgery.

Procedure of Corneal Cross-Linking Surgery

Corneal cross-linking surgery is a two-step process that involves the use of eye drops (riboflavin) followed by controlled exposure to ultraviolet (UV) light. The goal of this procedure is to regain the strength of corneal tissues of the eyes.

The ultraviolet light used in this procedure activates a process in which riboflavin creates some additional bonds between the connective tissues of the cornea that are made of collagen. This bond formation is called cross-linking and helps in making the cornea stronger and rigid so that it will maintain its shape.

The entire procedure of cross-linking involves the following steps:

Use of Anesthesia

The doctor uses some drops to numb the patient’s eyes. Some medications are also given so that the patients can relax.

Removal of Epithelium

In this step, the doctor removes epithelium layer of the patient’s eyes.

Use of Riboflavin

In this step, the doctor pours some drops of riboflavin eye drops which allow the cornea to better absorb light. The eye drops take almost half an hour to soak into the cornea.

Use of Ultraviolet Light

After giving the eye drops, patients are asked to lie back in a chair and then look up at a light. The UV light activates the riboflavin to form bonds between the collagen fibers which in turn makes the cornea stronger. While looking up at the light, the patient should not feel any pain because he/she is under the effect of anesthesia.

Use of Bandage

A contact lens is used which protects the eyes till they heal.

The entire cross-linking procedure completes in almost 60 to 90 minutes

Types of Corneal Cross-Linking

There are two types of cross-linking procedures depending upon whether the epithelium is removed or not during the application of riboflavin solution:

  1. Epithelium-off (epi-off) cross-linking
  2. Epithelium-on (epi-on) cross-linking

Epithelium-off (epi-off) Cross-Linking

In this type of cross-linking, the outer epithelium layer of the cornea is removed before using the riboflavin solution so that the eye solution will easily penetrate the deep corneal tissues.

This type of cross-linking is more effective but it increases the risk for infections and can also lead to clouding of the cornea.

Epithelium-on (epi-on) Cross-Linking

In this type, the outer layer of the cornea is left intact during the application of riboflavin solution which makes it a comparatively less invasive procedure than the epithelium-off (epi-off) cross-linking.

The doctor slightly loosens the epithelium layer before using the eye solution and hence keeps the epithelium intact. This method has fewer side effects and is also called transepithelial cross-linking.

Corneal cross-linking in advanced cases of keratoconus can be combined with other procedures for better results. For example, implantation of some tiny corneal inserts called “Intacts” can also be performed along with cross-linking for stabilizing the cornea.

Who are the Best Candidates for Corneal Cross-Linking?

Corneal cross-linking is most effective in patients who have less irregularity in their corneal shapes and also those who do not have any significant vision loss due to keratoconus. Patients who go for corneal cross-linking in their early stages of keratoconus receive more benefits from the procedure because cross-linking at early stages results in better visual acuity and an improved ability to wear contact lenses.

Patients with progressive ectatic disease of the cornea are also considered as the best candidates for corneal cross-linking. Besides, patients with diseases like Pellucid Marginal Degeneration, Terrien Marginal Degeneration, and post-refractive surgery (like LASIK or Radial Keratotomy) ectasia can also be the candidates for the cross-linking procedure.

Who are not Considered Suitable for Corneal Cross-Linking?

Patients with the following conditions are not ideal for corneal cross-linking procedure:

  • Having corneal thickness less than 400 microns
  • With concurrent infections
  • With severe corneal scarring
  • Having any history of poor epithelial wound healing
  • With Autoimmune disorders
  • With severe ocular surface disease (dry eye disease)

What Should you Expect from Corneal Cross-Linking?

After the cross-linking procedure (both epi-on and epi-off), your cornea should remain stable and also improve in its shape.

The procedure should also decrease the chances of severe vision loss in people with progressive keratoconus.

Risk Factors of Cross-Linking

Cross-linking is generally a safe procedure and saves people from undergoing corneal transplant surgeries. Occasionally, people develop problems due to cross-linking and following are some risk factors associated with cross-linking:

  • Corneal infection
  • Delayed healing of the corneal surface
  • Dry eyes
  • Failure of CXL which may lead to further CXL procedures
  • Irregularity in the corneal surface
  • Need for corneal transplant
  • Temporary or permanent loss of vision (temporary vision loss can be reversed with corneal transplant)

Precautions After the Procedure

After a CXL procedure, patients should be careful about the safety of their eyes and should take the following precautions:

  • Put the eye drops regularly as prescribed
  • Keep your eyes clean and avoid any exposure to dust as it may lead to eye infections
  • Get your eyes checked if you feel any problem
  • Avoid getting water into your eyes during a shower
  • Avoid swimming till the surface of your eyes heal
  • Avoid wearing contact lenses till your eye surface skin layer gets healed

Frequently Asked Questions

Corneal cross-linking is a non-invasive procedure performed in patients suffering from keratoconus. This procedure helps the patients in stabilizing their cornea and also makes the corneal tissues stronger. It is a two-step procedure in which a riboflavin eye solution is used followed by the exposure of UV light.


The UV light activates the riboflavin to form new bonds between the corneal fibers which in turn makes the corneal tissues strong, thereby helping in maintaining the corneal shape.

The recovery time for cross-linking procedure varies among the individuals depending upon their response to the treatment.


The normal recovery time is about one week; however, some patients may take a longer time to recover than this. The recovery time also depends upon how fast your corneal surface gets healed. Patients in which the healing period for the corneal surface is less show less recovery time.

No, the cross-linking surgery is not painful because doctors use anesthetic eye drops to numb the eyes of patients before the procedure is done. However, patients may feel some pain or discomfort after the procedure especially in case of epi-off cross-linking where the corneal epithelium is removed before the application of eye solution.

Corneal cross-linking lasts for several years and in some cases may be permanent as well (researches suggest). Patients who respond effectively to the corneal cross-linking procedure do not need to repeat it. However, the procedure may be repeated often if not effective.

The duration of cross-linking is almost one and a half hours if performed for both the eyes and approximately one hour if just one eye is being treated. After the procedure is completed, the patient may start noticing positive effects within 4 to 8 weeks. It usually takes at least 3 to 6 months for major vision improvement after the procedure.

Saima Andrabi

Saima Andrabi is a clinical biochemist and is passionate about driving knowledge platforms for creating health awareness in the general public. She pursued her master’s degree in clinical biochemistry from University of Kashmir, Srinagar followed by an internship from National Institute of pathology, New Delhi. Her areas of interest include molecular biology, immunology, medical physiology and forensic medicine. Saima is very much interested in writing medical content and wants to create awareness in public through this platform.


Currently, Saima Andrabi is working at Maxinov Solutions Private LTD as a research associate and is associated with DiseaseFix as a medical content writer.

Read More Articles by this Author