CXL FOR KERATOCONUS

One year after treatment, both standard and accelerated corneal crosslinking (CXL) protocols applied in eyes with corneal epithelium removed were more effective in treating keratoconus than accelerated CXL applied with the corneal epithelium intact, Minoru Tomita MD, PhD, Tokyo, Japan, told the 2014 American Academy of Ophthalmology annual meeting in Chicago.

Both standard and accelerated epi-off approaches reduced mean keratometry values, indicating corneal flattening, while accelerated epi-on did not. In addition to stabilising keratoconus progression, OCT imaging showed clear CXL demarcation lines more than 300 microns deep in the stroma for both epi-off techniques, compared with diffuse and transient crosslinking effects seen in the transepithelial or epi-on group.

Results of this one-year randomised prospective study suggest that the accelerated epi-on approach promotes crosslinking only in the anterior stroma, which may limit its effectiveness as a keratoconus treatment, Dr Tomita said.

OBSERVATIONS

Dr Tomita’s study involved 45 eyes of 23 patients with moderate keratoconus randomly assigned to receive standard CXL with epithelium off and 30 minutes exposure to 3.0mW/cm2 ultraviolet A, or accelerated CXL with epithelium off or on and two minutes 45 seconds exposure to 45.0mW/cm2 UVA. Patients were aged 21 to 39 years, showed evidence of keratoconus progression, had central cornea thickness of 400 microns or more, endothelial counts of 2,000 cells/cm2, and had no other ocular, corneal, immune system or other diseases that might complicate observations.

The 18 standard CXL cases were treated with a CCL-VARIO (PESCHKE Meditrade) device after 30 minutes pre-soaking with VibeX (Avedro) 0.1 per cent riboflavin solution with dextran. The 27 accelerated CXL cases were treated with the KXL (Avedro) device, with 14 epi-off pre-soaked for 10 minutes with VibeX Rapid (Avedro) 0.1 per cent riboflavin, and 13 epi-on pre-soaked for 10 minutes with ParaCel (Avedro) 0.25 per cent riboflavin, which includes HPMC and BAC to facilitate epithelial penetration.

One year after treatment the standard CXL group had statistically significant reductions in both mean and maximum keratometry values, while the accelerated epi-off group saw a significant reduction in mean K but not maximum K, and the accelerated epi-on group showed no changes.

The standard group recorded a small but significant reduction in mean corrected distance visual acuity, to -0.09 +/-0.11 logMAR from -0.12 +/-0.09 preoperatively, while both accelerated groups saw improved uncorrected visual acuity.

“Standard CXL and accelerated CXL are considered as effective treatments for keratoconus, whereas the efficacy of transepithelial accelerated CXL is limited to only anterior corneal stroma, indicating it is less effective compared to standard and accelerated CXL,” Dr Tomita concluded.

Minoru Tomita: tomita@eyecanmedical.com