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Sussex Eye Laser Clinic

What Is Corneal Crosslinking?

The clear outer layer at the front of the eye called “cornea” is responsible for focusing light so you can see clearly. It also filters out dirt, germs, and other things that can cause damage to the eyes. This part of the eye also plays a role in vision as it helps determine how well the eye can focus on close-up and far-away objects.


If it gets damaged by disease, injury, or an infection, it gets scarred and might distort the light entering the eye. Corneal disease like keratoconus may require special treatment and surgery in some cases.


One popular procedure that treats this corneal problem is corneal crosslinking, which we will discuss in depth. Read on.

The Deal with Keratoconus

Keratoconus refers to the corneal condition in which the clear, dome-shaped outer layer at the front of the eye thins out and weakens over time, gradually bulging outward into a cone shape. As this outer layer bulges into a thin cone shape, it distorts the vision and makes it hard to see. Although keratoconus often affects one eye more than the other, there are cases when it affects both eyes.


What are its symptoms?

Signs and symptoms of this corneal disease may change as it progresses. The most common symptoms of this condition include:


⦁ A need for frequent changes in corrected vision (eyeglass or contact lens prescriptions);
⦁ Blurred or distorted vision;
⦁ Increased sensitivity to glare and bright light (which may cause problems with night driving); and
⦁ Sudden clouding or worsening of vision.


What causes it?

As of writing, it’s still unclear what causes keratoconus. But most researchers think that people are likely to get this condition from birth. These factors may also have a link to corneal warping:


Family history

Does a family member have this condition? If so, you have a higher chance of getting it yourself. If you do have it, you might want to get your children’s eyes checked for signs of corneal weakening.



Keratoconus usually starts during the teenage years. But it might show up earlier in childhood. For some adults, they get diagnosed with this condition in their 30s. Although less common, it can also affect people who are in their 40s and older.



In one study of 16,000 people with this corneal condition, it was revealed that people who are Latino or Black are 50% more likely to get it than people who are white.



Allergies, asthma, atopic eye disease—any form of inflammation can break down the tissue of the outer layer of the eye.


Certain disorders

Relevant studies have found a connection between this corneal disease and systemic conditions like retinitis pigmentosa, osteogenesis imperfect, Ehlers-Danlos syndrome, and Down syndrome.


Eye rubbing

Another potential cause of keratoconus is eye rubbing. Rubbing the eyes hard over time can break down the eye’s clear outer layer. If you already have it, avoid rubbing your eyes as it can make keratoconus progress faster.


Can it be treated?

This corneal disease generally begins to affect individuals between the ages of 10 and 25. It may progress slowly for 10 years or longer, but it can be treated.


In its early stages, people diagnosed with keratoconus might be able to correct their vision problems with soft contact lenses or glasses, whichever option works best for them. Later, they may have to be fitted with rigid, gas permeable contact lenses. In some patients, other types of lenses like scleral lenses are the best possible option.


If keratoconus progresses to an advanced stage, an individual may need a cornea transplant. These standard surgical transplants have been around for many years, but a new treatment called corneal collagen crosslinking has been introduced to treat this corneal disease. This new treatment helps slow or stop keratoconus from progressing.


Some studies have shown that it can possibly prevent the need for a complete transplant in the future. In addition to the vision correction options we have previously mentioned, this treatment is also a safe option for individuals looking to treat their corneal condition.


Crosslinking: What Is It?

Also called CXL, corneal collagen crosslinking refers to the minimally invasive outpatient procedure to treat weakened or warped corneas. Like other parts of the body, the eye contains collagen which is an important substance that holds its cornea together. Diseases and surgery can harm this collagen.

With the CXL procedure, new collagen fibres are cross-linked together to strengthen and reinforce the cornea. The goal is to keep the outer layer of the eye from bulging more. CXL is the most up-to-date technology used to slow or stop the progression of corneal warping and steepening.


What Is Involved in CXL?

In corneal collagen crosslinking, doctors use ultraviolet (UV) light from a special machine and eyedrop medication to make the tissues in the eye’s outer layer stronger. As mentioned above, crosslinking adds bonds between collagen fibres in the eye. These fibres work like support beams to help the outer layer stay stable.


For your guidance, here’s an easy, step-by-step explanation of how the CXL procedure is done:


⦁ You will get drops to numb the eyes.
⦁ A specially formulated riboflavin (vitamin B) ophthalmic solution is applied to the surface of your eye. (It takes 30 minutes for the cornea to fully absorb the solution.)
⦁ It is immediately activated by a controlled exposure of the eye to ultraviolet (UVA) light from a special machine.
⦁ The combination of vitamin B eye drops and controlled exposure to UVA light trigger the bonding of collagen fibrils within the middle layer of your eye’s cornea.


The entire procedure takes about 60-90 minutes.


Two types of corneal collagen crosslinking:


Epithelium-off crosslinking

As its name suggests, this procedure involves removing the thin outer layer of the cornea called the epithelium. This allows the vitamin B ophthalmic solution to penetrate the deeper corneal tissue more easily.


Epithelium-on crosslinking

Also called transepithelial crosslinking, this procedure involves leaving the protective corneal epithelium intact. This makes it a less invasive procedure than epithelium-off crosslinking. Transepithelial crosslinking is still under clinical investigation, though. More data is needed to determine the safety and efficacy of this second crosslinking type.


Corneal collagen crosslinking can be combined with other procedures for the treatment of keratoconus. In more advanced cases of corneal disease, it can be performed along with implantation of tiny arc-shaped corneal inserts to reshape and stabilise the cornea. Crosslinking is most effective when it’s performed early in the disease, which is why early diagnosis is critical.


What to Expect Before, During, and After CXL



You will have to go through a preliminary evaluation first. This is for your eye doctor to measure the thickness of your cornea. The preliminary evaluation will determine if you are a good candidate for corneal collagen crosslinking.


Apart from this, you will also need to have a routine eye exam. This is to assess your overall vision and eye health. Corneal topography or the detailed mapping of the shape of your cornea will also be performed.


Don’t wear eye make-up, perfume, or after-shave the day of the procedure. You can eat a light meal and drink fluids beforehand. Just remember to follow your doctor’s instructions.



Depending on the technique used, the crosslinking procedure takes about an hour in most cases. If you are undergoing epithelium-off crosslinking, you can expect to have the epithelial layer removed from your cornea. Your surgeon will have to place you in a reclining position to perform this procedure. Riboflavin (vitamin B) eye drops will be placed on your eye.


For the epithelium-on or transepithelial procedure, you will be placed in a reclining position and riboflavin drops are then applied to your eyes. Your surgeon will evaluate your eye after enough time has passed. To proceed with the crosslinking, your cornea should absorb a sufficient amount of riboflavin.


Your surgeon will check the corneal thickness, too. UVA light from a special machine will then be applied for up to 30 minutes.



Regardless of whether you undergo epi-off or transepithelial crosslinking, expect a bandage contact lens to be placed on your eye. This is to reduce discomfort and facilitate healing. Your eye doctor will also prescribe topical and anti-inflammatory drops.


Since your eyesight will be affected, you will need someone to drive you home after your procedure. Like with most keratoconus patients who had the procedure done, your cornea will remain stable or improve in shape after a few weeks. This is highly significant for people with progressive keratoconus as severe vision loss is prevented.


Who Are the Best Candidates for Crosslinking?

As we have previously mentioned, this procedure is most effective if it can be performed before there is significant vision loss or before the cornea has become too irregular in shape. When applied early, corneal collagen crosslinking will result in better visual acuity.


This procedure can also be performed for the treatment of corneal ulcers that are unresponsive to treatment with topical antibiotics, and it can also be used to treat a host of corneal infections. Some studies have also found reasonable results in improving corneal shape in people who have undergone radial keratotomy.


If you are considering vision correction procedures like LASIK, you might also be pre-treated with corneal collagen crosslinking. This is to strengthen your eye’s surface before you undergo a laser ablation procedure that reshapes the cornea.


To reiterate, people diagnosed with any of the following conditions may be a candidate for this procedure:


⦁ Corneal ectasia (thinning and forward bulging of the cornea)
⦁ Corneal infections that are unresponsive to topical antibiotics
⦁ Corneal warpage
⦁ Irregular astigmatism
⦁ Keratoconus
⦁ Pellucid marginal degeneration


The procedure cannot be performed on patients if:


⦁ They have an active ocular disease other than keratoconus
⦁ Their cornea is too thin (less than 350-400 microns)
⦁ They have corneal scarring that significantly affects their vision
⦁ They have a corneal infection called herpes simplex keratitis caused by a cold sore or the herpes simplex virus
⦁ They have active, uncontrolled eye allergies
⦁ They are pregnant


What Are the Risks?

Like any other surgical procedures, there are risks associated with corneal collagen crosslinking. Since crosslinking includes the removal of the thin layer on the cornea’s surface or its epithelium, the risks may include:


⦁ Corneal epithelium defect caused by disruption of surface cells;
⦁ Delayed epithelial healing; and
⦁ Epithelial haze.


Some other reported risks (although very rare) include corneal opacity, visual acuity, stromal scarring, corneal striae (appearance of fine white lines in one’s field of vision). Infectious keratitis, herpetic keratitis, and ulcerative keratitis (severe inflammation of the eye) are other potential side effects.


Generally, corneal collagen crosslinking is minimally invasive and is associated only with a low rate of risks and complications. Consult your eye doctor about the possibility of side effects.


What Is the Downtime After Crosslinking?

Most people have reported going back to their normal daily activities after 1-2 weeks of crosslinking. For eye safety, it’s best to consult your doctor when it’s safe to resume your normal daily activities. It may take several months for your vision to be fully stable.


Your best-corrected vision (contacts or eyeglasses prescription) will likely change during this time. Your eye doctor will likely refit your glasses or hard contact lenses after six to eight weeks.


It merits repeating that crosslinking prevents the need for more serious surgeries like corneal transplants. Remember that this procedure does not make your existing corneal bulging and thinning go back to normal as its goal is to keep ectasia or keratoconus from getting worse. If the minimal downtime appeals to you, don’t hesitate to talk to your doctor. He/she can check if you are a good candidate for this procedure.


How Much Does Crosslinking Cost?

The average cost for this outpatient procedure is £1,950 per eye. The whole procedure may cost between £2500-£3000, including scans and consultations.


Ready to Make an Appointment?

Here at Sussex Eye Laser Clinic, we perform procedures like CXL to treat conditions that weaken the shape of the cornea. We also perform CXL combined with topography-guided laser eye surgery or photorefractive keratectomy. To discuss treatment options or to book a consultation, get in touch with us here at Sussex Eye Laser Clinic.


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