Examining advances in EPI-ON CXL for keratoconus

Take Home

Epithelial-on crosslinking seems to be effective and safe for treating keratoconus as the result of the combination of a new formulation of riboflavin with a higher level of ultraviolet light. This technique resulted in improvements in corneal shape, uncorrected visual acuity, and best spectacle-corrected visual acuity.

Dr. Trattler

By Lynda Charters; Reviewed by William B. Trattler, MD

Miami-Epithelial-on crosslinking (EPI-ON CXL) appears to be effective and safe for treating patients with keratoconus as the result of the combination of a new formulation of riboflavin with a higher level of ultraviolet (UV) light, based on data presented by William B. Trattler, MD.

This technique, said Dr. Trattler, from the Center for Excellence in Eye Care, Miami, resulted in improvements in the corneal shape, uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BSCVA).

Dr. Trattler noted that there has been resistance to EPI-ON CXL epithelial-on crosslinking because previously reported studies have found it to be less effective than EPI-OFF CXL. However, a closer inspection reveals that these published studies used flawed protocols for loading the epithelium. These protocols used a standard, timed protocol (usually 30 minutes) to load the cornea transepithelially, followed by immediate exposure to the UV light. These investigators never confirmed at the slit lamp that enough riboflavin was present in the cornea to actually react with the UV light, Dr. Trattler said.

With the EPI-ON CXL procedure-because the riboflavin can saturate the cornea irregularly-additional riboflavin loading may be needed.

Evaluating safety, efficacy

With this in mind, Dr. Trattler, along with Roy Rubinfeld, MD, and additional investigators evaluated the safety and efficacy of two formulations of riboflavin in EPI-ON CXL to treat patients with keratoconus.

Each formulation had a different UV light energy level, and the investigators evaluated the speed with which the riboflavin loaded into the cornea and the patient corneal and visual outcomes.

In this retrospective, multicenter, non-randomized study, riboflavin loading was stopped when the investigators determined that the cornea was saturated. The corneas treated with formulation 1 were exposed to 3 mW of UV light for 30 minutes, and the corneas treated with formulation 2 were exposed to 4 mW of UV light for 30 minutes. The changes in the UCVA, BCVA, spherical equivalent, and Kmax were determined at 6 and 12 months.

Dr. Trattler reported that in the 177 eyes treated with formulation 1, the average time of corneal loading was 59.3 minutes, the preoperative Kmax was 60 D, and the preoperative pachymetry was 447 µm. The respective data for the 168 eyes treated with formulation 2 were 27.2 minutes, 59.6 D, and 448 µm.

Results

The 12-month results in all eyes showed the superiority of formulation 2 in flattening of the Kmax. In the 56 eyes that completed the 12-month evaluation, the UCVA improved one or more lines in 63%, worsened in 14.8%, and was stable in 22.2%. The BSCVA improved one or more lines in 50%, worsened in 13%, and remained stable in 37%. Importantly, the average improvement in the Kmax compared with preoperatively was 0.98 D of flattening.

In the 76 eyes treated with formulation 1 that completed the 12-month evaluation, the UCVA data were similar, with 58.2% having an improvement of one or more lines, worsening in 7%, and stable vision in 34%. The BSCVA improved one or more lines in 53%, worsened in 27%, and remained stable in 20%. The average improvement in the Kmax compared with preoperatively was 0.66 D of flattening.

Subgroup analysis

Analysis of the data based on the preoperative Kmax value showed that the greater the Kmax value was, the higher the degree of flattening that was achieved. In patients with a Kmax of 50 D or more, treatment with formulation 2 resulted in 1.01 D of flattening compared with 0.74 D achieved with formulation 1. In patients with a Kmax of 56 D or more, the respective dD of flattening were 1.41 and 1.55.

The investigators summarized that, based on these results, the EPI-ON CXL is effective and safe for treating keratoconus, with improvements seen in the corneal shape, UCVA, and BSCVA.

A newer riboflavin formulation used with a higher energy level of UV light for 30 minutes resulted in faster loading times, improved flattening of the Kmax, and similar improvements in the UCVA and BSCVA. Evaluation of eyes with higher preoperative Kmax values showed that they had a strong response to CXL with either of the riboflavin formulations.

William B. Trattler, MD

E: wtrattler@gmail.com

Dr. Trattler has a financial interest in CurveRight and CXLO and is a consultant for CXLUSA.