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What is the best solution to improve the visual outcomes of cross-linking?
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Cross-linking and intracorneal ring segments
 Aylin Kiliç |
Intracorneal ring segments and cross-linking are the best combination in patients with keratoconus. The two techniques work synergistically, leading to better visual results and stability.
Cross-linking has an effect on the anterior corneal structure. After the treatment, a hyperreflective demarcation line, separating the cross-linked anterior corneal layers from the untreated area, is clearly visible by anterior chamber optical coherence tomography. Intracorneal ring segments work as spacer elements between bundles of corneal lamellae, producing an arc-shortening effect, mainly in the weak posterior part of cornea. Together, the two techniques improve the biomechanics of the entire corneal structure.
I have used this combination for many years with excellent results. Currently, I am using a new method that takes advantage of the intracorneal ring implantation procedure to perform corneal cross-linking without removing the epithelium. I carry out the two procedures simultaneously and inject riboflavin directly into the corneal channels to provide direct penetration of the photosensitizing agent without epithelium removal. This method overcomes the limitations of the transepithelial approach, as riboflavin can penetrate deeper into the corneal stroma, allowing the cross-linking effect to go as deep as in the conventional epithelium-off technique. Advantages of transepithelial cross-linking are no pain, early rehabilitation and no complications related with epithelial healing. In 22 cases treated with this method, with a follow-up ranging between 12 and 35 months, we did not observe any adverse effect. Riboflavin injection into the corneal channel for cross-linking treatment was found to be a safe and effective procedure.
Our results will soon be published in the Journal of Cataract and Refractive Surgery.
Aylin Kiliç, MD, is head of cataract and refractive surgery at Dunya Eye Hospital, Ankara, Turkey. Disclosure: Dr. Kiliç has no relevant financial disclosures.
Cross-linking and PRK
 A. John Kanellopoulos |
Since we introduced the concept of integrating corneal collagen cross-linking with partial topography-guided PRK in the mid-2000s, the demand for this combined treatment has grown tremendously. Performed simultaneously, partial topography-guided PRK first and then cross-linking, the two procedures work synergistically. Not only does keratoconus regress, as shown by topometric indices on the Pentacam maps (Oculus), but also the keratometric index of height decentration shows an improvement of about 50% to 70% in most cases, accounting for the improvement we see in best corrected visual acuity.
Using the WaveLight laser system (Alcon), we perform a 6.5-mm phototherapeutic keratectomy (PTK) followed by topography-guided partial PRK to normalize the corneal profile. After application of 0.02% mitomycin C for 30 seconds, we instill 0.1% riboflavin drops, not the dextran solution but sodium phosphate solution, which is less viscous. Cross-linking is then performed with higher fluence UV light, 7 mW/cm2 for 15 minutes. Bowman’s removal in PTK/PRK enhances riboflavin penetration and the efficacy of the cross-linking procedure, because the Bowman’s membrane can act as a barrier to the penetration of UVA light into the stroma.
It should be noted, however, that the combination of cross-linking and partial topography-guided PRK is not a refractive treatment but a therapeutic treatment. Refractive results are therefore unpredictable, and some eyes might even experience an increase in myopia postoperatively, as would be expected when normalizing an oblique cone. Nevertheless, no other treatment produces such a significant improvement in surface regularity and BCVA, as well as stabilization of keratoconus progression. We have reduced the number of transplantations for keratoconus by 90% over the last 10 years. And this statistic, I think, speaks for itself.
A. John Kanellopoulos, MD, is an OSN Europe Edition Editorial Board Member. Disclosure: Dr. Kanellopoulos is a consultant for WaveLight, Alcon, Bausch + Lomb, Ocular Therapeutix, Revision Optics, Avedro and Seros Medical.