Corneal Collagen Cross Linking
- Corneal Collagen Cross Linking (CXL)
With current methods using rigid contact lens or intra corneal ring segments, only the refractive error (spectacle numbers) can be corrected, but it has very little effect on the progression of keratoconus. It is estimated that eventually 21% of the keratoconus patients require surgical intervention to restore corneal anatomy and eyesight.
A new non surgical, non invasive treatment, based on collagen cross linking with Ultraviolet A (UVA, 365nm) and riboflavin (Vitamin B 2), a photosensitizing agent is now available. This changes the intrinsic biomechanical properties of the cornea, increasing its strength by almost 300%. This increase in corneal strength has shown to arrest the progression of keratoconus in numerous studies all over the world.
- What is Collagen Cross-linking and how is the treatment done?
It is a treatment for keratoconus which augments the collagen cross-links within the stroma of the cornea and so recovers some of the cornea’s mechanical strength.
The treatment is performed in our operation theatre under complete sterile conditions. Usually, only one eye is treated in one sitting. The treatment is performed under topical anesthesia (using anesthetic eye drops). The top most layer of the cornea is removed and then the cornea is treated with application of Riboflavin eye drops for 30 minutes. The eye is then exposed to UVA light for 30 minutes.
Hence, the treatment takes about an hour per eye. After the treatment, antibiotic eye drops are applied; a bandage contact lens may be applied, which will be removed by our doctor during the follow up visit. Protective eye wear, such as sunglasses is to be worn for a few days until complete healing takes place.
- Who can benefit from this treatment?
Collagen cross-linking treatment is not a cure for keratoconus, rather, it aims to slow or even halt the progression of the condition. This is important to understand. Patients may need to continue to wear spectacles or contact lenses (although a change in the prescription may be required) following the cross-linking treatment but it is hoped that it could limit further deterioration in the patient’s vision and reduce the case for keratoplasty.The main aim of this treatment is to arrest progression of keratoconus, and thereby prevent further deterioration in vision and the need for corneal transplantation.
- What are the risks and consequences involved?
Very few potential risks associated with this treatment have been reported so far.
The treatment involves the removal of outer layer (epithelium) of the cornea:
There is therefore discomfort and a short-term haze.
Other lesser but more common risks include:
Inability to wear contact lenses for several weeks after the treatment
Changes in corneal shape necessitates fitting of a contact lens or an occasional change in spectacle correction.
As is the case with any treatment, there may also be long-term risks that have not yet been identified.
The increased corneal rigidity induced may wear off over time and further periodic treatments may be required.
Are there any published studies for the same?
- In published European studies, such treatments are proven safe and effective in patients.
The 3 and 5 year results of Dresden clinical study in human eyes has shown arrest of progression of keratoconus in all treated eyes. (Wollensak G. Crosslinking treatment of progressive keratoconus: New Hope.
Current Opinion in Ophthalmology 2006; 17: 356 – 360). Biomechanical measurements have shown an impressive increase in corneal rigidity of over 300% after crosslinking.
The Dresden, Germany clinical study has shown that in all treated eyes the progression of keratoconus was stopped (‘freezing’).
In over 53% of those eyes there was a slight reversal and flattening of the keratoconus by up to 2.87 diopters. Best corrected vision improved by 1.4 lines. This technique has shown great promise in treating early cases of the disease.
- Advantages of Cross Linking
2. Simple- Single-one hour treatment
3. No follow up sittings required
4. No need for admission
5. Stops the progress and causes regression of disease
6. Does not need eye donation as in corneal transplant
7. No major precautions
8. No injections or stitches
9. No incisions as in Intacs or Corneal ring segments
10. Quick recovery with short follow up