Accelerated CXL rivals conventional technique

Chicago-Results from 2 years of follow-up in a large, prospective comparative study show that conventional corneal crosslinking (C-CXL) and accelerated CXL (A-CXL) are similarly safe and effective for stabilizing keratoconus progression in eyes with mild-to-moderate disease, said Tulika Chauhan, MD, at AAO 2016.

“Measurement of differences in the depth of the demarcation line would add credibility to the observations in our study, and we hypothesize that if there is a real difference between A-CXL and C-CXL, it may become evident over the longer term,” said Dr. Chauhan, Cornea and Phaco-Refractive Department, Vasan Eye Care Hospital, New Delhi, India.

Asked about how the study findings have influenced practice at her institution, Dr. Chauhan noted that A-CXL is now the preferred technique.

The study evaluated the effects of C-CXL and three A-CXL protocols on visual, refractive, topographic, and safety outcomes in a group of 162 eyes of 111 patients.

To be eligible for inclusion, eyes had to have a thinnest pachymetry measurement ≥400 microns and show evidence of keratoconus progression over the previous 12 months based on at least one of the following changes: increase in steepest keratometry ≥1 D; increase in steep meridian curvature ≥1 D; loss of ≥2 lines BSCVA attributable solely to keratoconus progression; ≥1 D change in astigmatism determined by manifest subjective refraction.

In all groups, CXL was performed with an epithelium-off technique using 0.1% riboflavin with 20% dextran solution applied every 2 minutes and a total irradiance of 5.4 J/cm². The C-CXL protocol involved irradiation with 3 mW/cm² for 30 minutes. In the A-CXL groups, irradiation was delivered at 9 mW/cm² for 10 minutes, 18 mW/cm² for 5 minutes, or 30 mW/cm² for 3 minutes.

“We designed the treatment protocols to provide equivalent radiation exposure using the same formulation of riboflavin to address potential confounding variables,” Dr. Chauhan said.

All groups received the same postoperative care, and they were well matched for age and gender distribution.

Outcomes

The outcomes analyses showed that at 2 years after treatment, mean UCVA and mean BSCVA were significantly improved in all CXL groups, and there were no eyes that lost lines of BSCVA.

The refractive analysis showed that in all four groups, mean spherical equivalent was significantly reduced 2 years after CXL.

In addition, all treatment protocols were associated with statistically significant reductions in the flat keratometry and steep keratometry values (mean flattening 1.76 and 2.09 D, respectively).

Central corneal thickness, thinnest pachymetry, and endothelial cell counts did not change significantly, and no inter-group differences were noted in these endpoints, Dr. Chauhan noted.

Discussing the study’s limitations, Dr. Chauhan mentioned small sample size.

However, in the discussion following her talk, panel member James J. Reidy, MD, University of Chicago, noted that the study population was large relative to other investigations that have compared conventional and accelerated CXL.