Laird Harrison

May 06, 2015

SAN DIEGO — Corneal collagen crosslinking reduces the risk for ectasia in LASIK patients, a new study suggests.

Although the study did not detect an effect of crosslinking on visual acuity, it did show less steepening in patients with high myopia in crosslinked corneas, said John Kanellopoulos, MD, from the Laservision.gr Institute in Athens, Greece.

He presented the finding here at the American Society of Cataract and Refractive Surgery 2015 Symposium.

During the procedure, clinicians apply a riboflavin ophthalmic solution (Photrexa, Avedro) and then expose the cornea to ultraviolet light, which increases the bonds between collagen fibrils, stiffening the cornea.

The drug and procedure, widely used in Europe, are still under review by the US Food and Drug Administration. Cautious approval of the technique was recommended earlier this year.

Crosslinking has been used to treat keratoconus, but Dr Kanellopoulos and his colleagues wanted to see if it could be used to prevent ectasia, which occurs in some LASIK patients.

They treated 65 eyes with LASIK and crosslinking and another 75 eyes with LASIK alone.

For the most part, changes before and after the surgery were similar in the two groups. However, in patients with high myopia, changes in midperipheral epithelial thickness were less pronounced in the group treated with LASIK and crosslinking than in the group treated with LASIK alone.

Table. Measures Before and After Surgery

Variables LASIK and Crosslinking LASIK Alone
Mean value, diopter    
   Refraction at baseline –6.75 –5.33
   Postoperative refraction 0.25 0.27
   Steep corneal curvature at baseline 45.15 44.03
   Steep corneal curvature at 12 months 38.37 38.66
Midperipheral epithelial thickness, µm    
   Very high myopia (–8 to –9 diopters) 3.79 9.75
   High myopia (–7 to –8 diopters) 3.95 7.14

 

"This is a very difficult study to perform to begin with because, obviously, the preferred outcome is to see which eye would develop ectasia," Dr Kanellopoulos said during his presentation.

"We know that ectasia is extremely rare. When we look at the usual numbers — meaning refractive outcome, visual acuity — the two groups are very similar. The difference, though, is in looking at epithelial profiles," he explained.

Dr Kanellopoulos reported that his group will soon publish an ex vivo study showing biomechanical evidence that crosslinking increases stability of the residual cornea in LASIK surgery.

"It is up to the surgeon whether they want to reintroduce the biomechanical stability of the cornea," he said. "Experience has shown that it's not absolutely necessary, but if you're doing high-myopic LASIK in a population that has a very high incidence of keratoconus, you may consider it more carefully."

The technique shows potential, said session moderator Elizabeth Hofmeister, MD, from the Navy Refractive Surgery Center in San Diego, California.

"It was a great paper," she told Medscape Medical News. "It's pretty incredible for people who could be at high risk for getting this stretching out."

But there is currently no way to determine which LASIK patients are at increased risk for ectasia, she added.

Dr Kanellopoulos reports financial relationships with Alcon, Allergan, Avedro, and i-Optics. Dr Hofmeister has disclosed no relevant financial relationships.

American Society of Cataract and Refractive Surgery (ASCRS) 2015 Symposium. Presented April 21, 2015.

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