"Three essential ingredients are needed for this reaction-riboflavin (vitamin B2), UV light (ideally, 360 to 365 nm), and oxygen. In the presence of corneal collagen, these three ingredients create free radicals that in continuum run a biochemical reaction to cross-link normal human collagen fibers," Dr. Kanellopoulos explained. He is associate professor of ophthalmology, New York University Medical School, New York, and director, LaserVision.gr Institute, Athens, Greece.
He described his first case in which UVA CCL was used. A 24-year-old man underwent unilateral LASIK, which improved the vision from 20/80 to 20/20 best spectacle-corrected visual acuity with ablation to treat mild myopia. The patient initially reported vision to be good. Subsequently, however, vision deteriorated. The operating surgeon diagnosed ectasia and recommended implanting intrastromal corneal ring segments (Intacs, Addition Technology), an approach that did not improve the patient's vision.
The patient had substantially improved visual function and corneal regularity by 4 years after treatment but developed haze, which has resulted in a refinement of the procedure, Dr. Kanellopoulos reported. He also noted that the status of the cornea continued to improve over time during follow-up.
Based on this experience and that with other patients, Dr. Kanellopoulos said he now performs both treatments simultaneously instead of waiting for 6 months to perform UVA CCL.
"We started doing both treatments at the same time. The ablation treatment aimed to correct about half of the refractive error with cross-linking. This change in strategy has resulted in an impressive change in keratometry in subsequent patients," he reported.
To date, Dr. Kanellopoulos said, he and his colleagues have used UVA CCL on more than 500 patients. He demonstrated how the cornea has a glass-like appearance with fine lines after the treatment. Importantly, the visual acuity has improved in all eyes, and deterioration toward ectasia has not occurred in any corneas.
"The advantage to combining treatments is that the patient has to undergo one procedure; there is less scarring. The visual rehabilitation has been gratifying," he said. "A caveat is that the refraction delivers more treatment than expected in these cases, and there is a need for nomogram adjustments.
"Of particular note is that, in my practice, this treatment approach has reduced the need for penetrating keratoplasty by 70%. Obviously, studies with longer follow-up are needed to validate our data," Dr. Kanellopoulos concluded.