June 23, 2022 | Keratoconus, Basecamp

The Complete Walk-through of the Corneal Cross Linking Procedure

By Barrett Eubanks, M.D.

The Complete Walk-through of the Corneal Cross Linking Procedure

Wonder what you can expect going through corneal cross linking to treat your keratoconus? Wonder no more! Fortunately, it's a very straightforward and easy procedure to go through, it just takes a little time.

Corneal cross linking in the United States has three major steps. The surface layer of the cornea called epithelium is brushed off, special eye drops are added to absorb into the cornea and lastly a UV light is shone onto the eye, interacting with those eye drops to cause the cross linking effect.

There is some additional prep beforehand and a few small things afterwards, but we’ll cover it all in today's walk-through of corneal cross linking.

Step Zero - Getting You Ready For Corneal Cross Linking

Wait! Before we get onto the procedure, there are some steps to get you ready for it.

You will be given drops and typically some relaxing medication to prepare you.

The eye must be numb for corneal cross linking. Fortunately, there are eyedrops which do just that. These eye drops work within seconds to block out all pain on the cornea. Very effective!

You’ve probably already gotten these drops on a visit to see the eye doctor. These same drops are used routinely for standard eye exams. When the eye drop is placed in your eye, you will have a burning pain for a few seconds until the eye drop takes effect.

And yes, you can continue on to the procedure with just that. But let’s face it, eye surgery is stressful. So, often you will get a xanax or valium to help relax you a little more and make it easier to have your corneas cross linked.

Ok, on to the procedure!

Step One - Preparing The Cornea For Treatment

Cornea Cross Linking actually exists in various forms. You may run across different terms such as “epi-on" or “epi-off" or “accelerated cross linking" (and also commonly abbreviated as CXL). And truth is, corneal cross linking is an evolving treatment. While we already know quite about it, as we learn more about what exactly is needed, we continuously refine the procedure to make it quicker and easier.

But in the United States, there is only one FDA approved variation of corneal cross linking. This is the “epi-off" version and this is the one being covered in today’s walk-through.

So what does “epi-off" actually mean? Well, on the surface of the cornea is a thin layer of cells called epithelium. This epithelium serves the vital role of protecting our cornea. It's a barrier to prevent things from passing into the corneal layers below.

Having a barrier is normally great! But that can be a problem with corneal cross linking.

During corneal cross linking, a special eye drop containing the vitamin riboflavin is allowed to absorb into the cornea. But that barrier from the epithelium can prevent this eye drop from adequately absorbing.

So the very first step of corneal cross linking is to remove this epithelium layer. (Don’t worry, it grows back within a week after corneal cross linking).

During this step, your surgeon will bring you underneath a microscope and employ one of several techniques to remove the epithelium. These are the same techniques also used for the laser eye surgery PRK. This can include using a small rotating brush to mechanically remove that layer, or using absolute alcohol to cause that layer to detach on its own (followed by manually brushing of that detached layer).

But the good news is that none of those steps are painful! Remember those numbing eye drops you got? Those eye drops take care of all pain. But you still may or may not have some additional pressure sensations.

Also, no need to worry about blinking during this step. An eyelid holder is placed underneath the eyelids to hold the eyelids off the cornea and prevent blinking from being any issue. Note: this eyelid holder can sometimes be uncomfortable as it stretches the eyelids or pushes against the bone around your eye. It will also be uncomfortable if you squeeze down real hard on the eyelid holder.

Your vision will become blurry during this step. As that smooth epithelium layer is removed, the cornea becomes rougher and the vision will be blurrier for the remainder of the procedure.

Step Two - Add Eye Drops

This step is really as easy as it sounds. During this step, you’ll likely be moved to a different bed to lie down on. And every few minutes the doctor (or more commonly one of the doctor’s technicians), will place one of the riboflavin drops on your eye.

This drop has a yellow color and thus everything in your vision will become more yellow.

Riboflavin vitamin eye drops
Riboflavin vitamin eye drops

These drops continue for at least 30 minutes in order to make sure that the eye drop has soaked in well enough into the cornea.

Again, not painful, but does get a little boring lying there getting eye drops.

Step Three - The Treatment!

Finally we get to the actual corneal cross linking treatment. The epithelium is off, the cornea is saturated with riboflavin, it is time to apply the UV light.

The doctor / technician will bring the UV light in front of your eye. And for the next 30 minutes you look at this light.

That same eyelid holder you had in step one is used again so that you don’t have to worry about blinking as you affix your gaze on the UV light.

Once again, you may be bored.

But a short 30 minutes later and you are done!

Step Four - Post Procedure

Now that your eye is successfully treated with the UV light, all that's really left is to place a contact lens on the surface of the eye. This contact lens doesn’t have any prescription, it is purely designed for comfort.

The cornea is the most sensitive structure in the body. This is why touching your eye is painful. But the epithelium on the surface of the cornea protects us from even more pain. When this epithelium is off, the cornea can experience intense pain from simple things such as the movement of your eyelid over the cornea. That would be a very uncomfortable recovery.

So to make the recovery easier, a contact lens is placed to act almost like a “temporary epithelium" to protect the cornea and prevent much of that pain. This helps keep the eye more comfortable until the epithelium is able to heal over.


Corneal cross linking is a very easy and straightforward procedure. There are just a few simple steps. The procedure is pain free but expect it to take over an hour for the full FDA approved treatment.

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