corneal collagen cross linking procedure
Corneal collagen cross-linking procedure
Adverse effects
Types of Corneal Cross-Linking
Procedure
Benefits
What are the side effects of cross linking?
How long does it take to get vision back after cross linking treatment?
What to expect after crosslinking?
How long is cross linking surgery?
How successful is cross linking?
How long does it take to recover from corneal cross linking?
Does collagen cross linking improve vision?
Is corneal cross-linking like LASIK?
Corneal collagen cross-linking with riboflavin (vitamin B2) and UV-A light is a surgical treatment for corneal ectasia such as keratoconus, PMD, and post-LASIK ectasia.
It is used in an attempt to make the cornea stronger. According to a 2015 Cochrane review, there is insufficient evidence to determine if it is useful in keratoconus. In 2016, the US Food and Drug Administration approved riboflavin ophthalmic solution crosslinking based on three 12-month clinical trials.
Cross linking is currently the only available treatment which appears to stop the worsening of keratoconus. Clinical trials based on outcomes 1 year after cross-linking show success in the halting of keratoconus in more than 90% of treated eyes, with more than 45% of eyes also gaining an improvement in corneal shape. A separate study over a 5 year period showed a similar success rate in halting the progress of keratoconus. Visual improvement after treatment occurs in approximately 50% of cases. However, after treatment you will still need to wear spectacles or contact lenses.
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Adverse effects
Among those with keratoconus who worsen CXL may be used. In this group the most common side effects are haziness of the cornea, punctate keratitis, corneal striae, corneal epithelium defect, and eye pain. In those who use it after post-LASIK ectasia, the most common side effects are haziness of the cornea, corneal epithelium defect, corneal striae, dry eye, eye pain, punctate keratitis, and sensitivity to bright lights.
There are no long term studies about crosslinking effect on pregnancy and lactation. According to a manufacturer crosslinking should not be performed on pregnant women.
People undergoing crosslinking should not rub their eyes for the first five days after the procedure.
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Types of Corneal Cross-Linking
There are two types: epi-off and epi-on. “Epi” is short for epithelium, a layer of tissue that covers your cornea.
- Epithelium-off cross-linking. In this procedure, the thin outer layer (epithelium) of the cornea is removed to allow the liquid riboflavin to more easily penetrate the deeper corneal tissue.
- Epithelium-on cross-linking. In this procedure (also called transepithelial cross-linking), the protective corneal epithelium is left intact, making it a less invasive procedure than cross-linking with epithelium removal.
Procedure
The treatment involves removing the superficial layer (epithelium) from the surface of the cornea and then applying Riboflavin eye drops to the eye for 30 minutes. The eye is then exposed to UVA light for another 30 minutes. After the treatment, a bandage contact lens is worn for 1-3 days until the surface of the eye has healed. Antibiotic and steroid eye drops are also prescribed for a few weeks.
Benefits
It is important to understand that collagen cross-linking treatment is not a cure for keratoconus. Rather, it aims to slow or even halt the progression of the condition. After the treatment, it is expected that it will continue to be necessary to wear spectacles or contact lenses (although a change in the prescription may be required). However, it is hoped that the treatment will prevent further deterioration in vision and the need for corneal transplantation.
Thus initially the treatment would be offered only to patients in whom there is clear evidence of progression of their keratoconus. A person whose keratoconus is already so bad that it cannot be corrected by contact lenses is unlikely to gain any benefit from this treatment. In this situation a corneal transplant is usually required.
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What are the side effects of cross linking?
There are a number of potential risks associated with this treatment although very few complications have been reported so far.
Ultraviolet light is potentially harmful to the eye. However, the dose used is designed to prevent observable damage to the sensitive cells that line the back of the cornea (endothelium) or the other delicate structures within the eye eg lens and retina. No lens opacities (cataracts) have been attributed to this treatment in European trials.
The treatment involves the scraping away of the outer layer (skin or epithelium) of the cornea. There is therefore a risk that the surface of the cornea will be slow to heal. Infection may occur which could lead to the development of corneal scarring. Antibiotics are routinely used to prevent this complication. Corneal scarring might necessitate further surgical procedures (including corneal transplantation) though this is extremely rare.
Other lesser but more common risks include:
- Inability to wear contact lenses for several weeks after the treatment.
- Changes in the shape of the cornea necessitating a refitting of a contact lens or a change in the spectacle correction.
- As is the case with any experimental treatment, there may also be long-term risks that have not yet been identified.
- The increased corneal rigidity induced by exposure to UVA and riboflavin may wear off over time and further periodic treatments may be required, raising the possibility of other side effects from repeat doses of the treatment.
How long does it take to get vision back after cross linking treatment?
With the traditional CXL procedure, most patients find that immediately after the cross-linking treatment, their vision is actually worse than it was before the procedure. This usually goes on for roughly 3-6 weeks. Patients may start to notice positive effects 4-8 weeks after the procedure and may experience major improvement in vision at least 3-6 months after the investigational procedure. In some studies patients’ vision and astigmatism were still continuing to improve five years after the cross-linking procedure so visual improvement is a long process. With the less invasive transepithelial CXL, some patients found their vision improved as early as several weeks after treatment.
What to expect after crosslinking?
After a cross-linking procedure, your eyesight will be blurry at first. You may notice changes in your vision from time to time to time during the healing process. You may be more sensitive to light and have poorer vision for about 1-3 months after the surgery.
The goal of corneal cross-linking is to slow your disease and prevent future vision problems, but in some cases, your eyesight may get better over time.
Once you’ve had corneal cross-linking, you might need new glasses or contacts.
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How long is cross linking surgery?
Your doctor will put in specially formulated riboflavin (vitamin B2) eyedrops, which allow your cornea to better absorb light. It takes about 30 minutes for the drops to soak into your cornea.
Then, you’ll lie back in a chair and look up at a light. You shouldn’t feel any pain during the procedure because your eyes will be numb. The entire treatment takes about 60-90 minutes.
How successful is cross linking?
It is very effective, the success rate is more than 95% for an 'epi-off' treatment. In the remaining 5% of patients where there is further progression or change, a second treatment may be required. Overall, success rates for corneal cross-linking are considered to be very high. When the first human trials for the procedure were performed in 2003, all patients suffering from progressive keratoconus saw the progression stop. In addition, 70 percent of the patients had a decreased keratoconus, and 65 percent experienced visual acuity.
Corneal cross-linking procedures have improved and evolved since 2003. Success rates show an average decrease in keratometry of nearly 75 percent, and visual acuity improvements of more than 70 percent. These findings are stable a full year after the procedure.
Complications for corneal cross-linking are rare, but there can be risks, as with any surgical procedure. Your cornea will need to be thick enough for the procedure to be effective, and there is always a small risk for infection.
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How long does it take to recover from corneal cross linking?
The treated eye is usually painful for 3 to 5 days, however levels of discomfort vary from patient to patient. Recovery time is about one week although most patients may find that it may be slightly longer.
After treatment expect to take up to one week off work and for some patients who experience complications this could be longer. You will not be able to drive for at least a week. After treatment this may be severe. It is important to rest as much as possible during these days to let the eye heal. If you partake in activities or sport, please ask your doctor when these may be resumed.
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Does collagen cross linking improve vision?
However, corneal collagen cross-linking – an advanced procedure approved by the U.S. Food and Drug Administration (FDA) in 2016 – can vastly improve vision in patients of all ages. Corneal collagen cross-linking (CXL) is not a cure for keratoconus, but it can help prevent the condition from getting worse. CXL is intended to prevent steepening or progression of the keratoconus process to potentially avoid needing a corneal transplant. Unlike some other vision disorders, keratoconus affects how light enters the eye and can distort how that light is interpreted by the brain. But CXL is actually a treatment to help strengthen the cornea to decrease or halt disease progression.
Is corneal cross-linking like LASIK?
No. LASIK is a procedure that reduces or, in some cases, may even eliminate the need for glasses or contact lenses by removing corneal tissue. The cross-linking treatment does not remove tissue. The purpose of cross-linking is to prevent further deterioration of vision for most patients and to potentially improve vision. Patients will typically require a lower eyeglass prescription or can have an easier time being fit with contact lenses.
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