Epi-on cross-linking is a form of corneal cross-linking in which the surface layer of the cornea, the epithelium, is left in place during treatment. The goal is the same as standard cross-linking: to strengthen the cornea and help slow or stop progression in keratoconus and corneal ectasia. The main appeal of epi-on CXL is a more comfortable recovery and a lower surface-healing burden than epi-off treatment.
To strengthen the cornea and help reduce the risk of progression in keratoconus and corneal ectasia, while preserving the surface epithelium during treatment.
Selected patients with progressive corneal ectasia, depending on corneal thickness, age, disease behavior, and the treatment goal.
Usually an outpatient procedure.
Less discomfort, less surface-healing stress, less infection risk, and typically faster visual recovery than epi-off CXL.
Epi-on cross-linking is designed to address the same underlying problem as standard cross-linking: a cornea that is becoming biomechanically weaker and progressively changing shape. In keratoconus and corneal ectasia, the cornea can thin and bulge, leading to worsening irregular astigmatism, blur, glare, and loss of visual quality. Cross-linking helps make the cornea more resistant to further deformation.
What makes epi-on different is not the goal, but the route. Instead of removing the epithelium first, the treatment keeps that surface layer intact and uses special strategies to get riboflavin and oxygen where they are needed. That makes the procedure more comfortable for many patients, but it also creates technical challenges that have historically made epi-on less effective than epi-off unless the protocol is carefully designed.
How It works
Your cornea is made largely of collagen – tightly organized protein fibers arranged in layers. In a healthy cornea, these fibers are well-bonded to one another, giving the cornea the structural integrity it needs to maintain its shape and focus light correctly onto the retina.
In keratoconus, some of these bonds between collagen fibers are weak or absent. Over time, without enough structural support, the cornea gradually bulges forward and thins – leading to increasing distortion of vision that glasses and standard contact lenses struggle to correct.
Cross-linking works by creating new covalent bonds between collagen fiber strands, effectively “locking” the corneal structure in place. After the procedure, the cornea is measurably stiffer and less prone to the deformation that drives keratoconus progression.
Compare
Comparison Parameters
Epi-on CXL
Transepithelial
Epi-off CXL
Standard / Dresden Protocol
Watch a video of an epi-on CXL procedure being performed at the slit lamp, showing how our advanced technique works in a clinical setting.
Step-by-step guide
Knowing exactly what to expect can make a real difference in how comfortable you feel going into a procedure. Here is what a typical epi-on cross-linking experience looks like at ELZA Institute.
Arrival and preparation
You will be welcomed by our team and guided through the process. Once settled, anesthetic eye drops are applied to both numb the eye surface and keep you comfortable throughout.
Riboflavin application
Specially formulated riboflavin drops are applied to the eye at regular intervals over a soaking period. In the epi-on approach, these drops are designed to penetrate the intact epithelium and reach the corneal stroma below. This preparation phase is essential — it ensures the cornea is fully saturated with riboflavin before UV-A exposure begins.
UV-A light treatment
A precise, calibrated beam of UV-A light is directed at the cornea for a set period. This activates the riboflavin and initiates the cross-linking reaction within the corneal collagen. The light delivery is carefully monitored and controlled throughout.
Completion and aftercare
Once the treatment is complete, antibiotic and anti-inflammatory eye drops are applied. Depending on your individual case, a soft bandage contact lens may be placed on the eye to protect the surface and maximize comfort as the eye settles. The procedure itself typically takes between 60 and 90 minutes.
Before leaving the clinic, your eye will be examined and you will receive your prescription eye drops along with clear written instructions. Our team will confirm your follow-up appointment schedule before you go.
While epi-on CXL has made great strides, epi-off CXL remains the go-to option for certain cases.
The Dresden Protocol, the original epi-off method, is still the most powerful tool for treating advanced and aggressive forms of keratoconus. When the greatest mechanical strength is needed, epi-off provides the most robust support.
ELZA has developed a high-fluence epi-off protocol that significantly shortens treatment time without sacrificing efficacy. Using up to 7.5 J/cm² of UV light, our high-fluence method delivers the same mechanical strength as the standard 30-minute Dresden protocol – but in just a third of the time.
While epi-on CXL offers many advantages, especially in terms of faster recovery and fewer risks, epi-off CXL remains the treatment of choice in certain severe cases where maximum mechanical strength is necessary.
At ELZA, we are constantly refining our techniques to provide the most effective and personalized treatments. Whether using epi-on or epi-off, our goal is to ensure that each patient receives the best care possible, tailored to their specific needs.
Why us?
Corneal cross-linking is a procedure where experience, precision, and individualized care make a significant difference in outcomes. Here is what distinguishes ELZA Institute.
Our team includes specialists who are internationally recognized for their work in keratoconus and corneal ectasia. Cross-linking is not a peripheral service for us — it is a core part of what we do, and our specialists have performed this procedure in very high volumes across a wide range of patient presentations.
Every patient undergoes a comprehensive corneal evaluation before any treatment decision is made. This includes high-resolution corneal tomography, pachymetry (corneal thickness mapping), and detailed wavefront analysis. We use this data to confirm the diagnosis, assess the rate of progression, and determine precisely which treatment — and which approach — is right for your cornea.
We regularly welcome patients from across Europe, the United States, the Middle East, and beyond. Our team includes English-speaking staff, and we can assist with planning your visit — from pre-travel diagnostics to coordinating follow-up care with your ophthalmologist at home.
FAQs
Modern epi-on protocols produce excellent stabilization results that are comparable to epi-off for many patients, particularly in the early to moderate stages of keratoconus. The epi-off approach has a longer track record and remains the standard for certain presentations. Your specialist will recommend the approach with the strongest evidence base for your specific situation.
Anesthetic eye drops are used throughout, so you should not feel pain during the procedure. With epi-on cross-linking, post-procedure discomfort is generally very mild — most patients describe it as minor light sensitivity or a gritty sensation for a day or two. This is considerably less than the 3–5 days of significant discomfort some patients experience after epi-off.
The full appointment, from preparation to completion, is typically 60 to 90 minutes. You will not need to be admitted to hospital — this is an outpatient procedure performed in our clinic.
Most patients return to desk work and normal daily activities within 1 to 2 days. If your work involves driving, heavy physical activity, or environments where eye protection is essential, please discuss this with your specialist during your consultation.
You will receive personalized pre-operative instructions after your consultation. Generally: remove soft contact lenses a few days before your appointment, arrange transportation home (you should not drive), and bring a list of any medications you take. On the day, wear comfortable clothing and avoid wearing eye makeup.
We have experience coordinating care for international patients and can help you plan your visit efficiently. In many cases, the diagnostic evaluation and the procedure itself can be scheduled during a single trip of a few days, with follow-up imaging arranged with a trusted specialist in your home country. Contact our international patient team to begin the conversation.
In most cases, yes. Cross-linking stabilizes the cornea — it does not correct the refractive error (blurred or distorted vision) caused by the irregular corneal shape. After the cornea has been confirmed as stable, your specialist may discuss additional options for vision correction if that is a goal. Many patients with keratoconus use specialized contact lenses (such as scleral or hybrid lenses) even after successful cross-linking.
In some cases, cross-linking can be performed on both eyes during the same visit. In other cases, a staged approach — treating one eye, then the other — is preferred. Your specialist will advise you based on the progression and symmetry of your condition.
In epi-off, the surface epithelium is removed before treatment. In epi-on, it is left in place and special strategies are used to help riboflavin penetrate. Epi-on is generally more comfortable, while epi-off still remains important for cases needing the strongest biomechanical effect.
Coverage depends on your specific insurance plan and the clinical indication. We recommend contacting your insurer directly and obtaining a prior approval before your procedure. Our patient coordination team can assist you with the documentation needed for this process.
Yes. In fact, keratoconus tends to progress more rapidly in younger patients, which makes early treatment particularly important in this age group. Epi-on cross-linking is well tolerated by children and adolescents, and its lower discomfort profile can make the experience more manageable for younger patients. Parental consent and a thorough pre-operative assessment are required.
Long-term data from epi-off cross-linking — which has been performed since the late 1990s — shows that the stabilizing effect is durable, with many patients maintaining stability for 10+ years. Epi-on has a shorter evidence history but current data is encouraging. In rare cases, keratoconus may continue to progress after cross-linking, in which case a repeat procedure can be considered.
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