Prof. Farhad Hafezi, MD, PhD, FARVO is the Medical Director at The ELZA Institute, was recently interviewed by Ocular Surgery News (OSN), where he spoke about advancing CXL technology for the treatment of corneal ectasias like keratoconus. The interview covered three main topics.
The sub400 protocol advancing CXL in thin corneas
Historically, cross-linking procedures were excluded from patients with corneas that were thinner than 400 µm, to leave a ~70 µm uncross-linked safety margin region at the cornea. However, as many patients with advanced disease had thinner corneas, many were left untreated. In 2007, Prof. Hafezi and his colleagues sought to address this problem and introduced hypo-osmolar riboflavin to swell these thin corneas to a thickness greater than 400 µm before cross-linking with UV irradiation commenced. More recently, the team has developed the sub400 protocol, which involves customizing UV irradiation duration to each patient’s corneal thickness measurement. Prof. Hafezi told OSN that this “modifies the duration of UV irradiation at 3 mW/cm² to achieve the desired depth needed to cross-link each patient’s cornea and leave a 70 µm safety margin.” The reason this is possible is thanks to earlier work where Prof Hafezi and his collaborators were able to model all of the components of the CXL photochemical reaction: riboflavin, corneal tissue, oxygen availability, and UV light intensity and duration.
Higher Fluence and Intensity
Ocular Surgery News was also told that his research group is also exploring ways of advancing CXL technology and treatments, principally by making them faster by using higher UV light intensities. Thanks to their modeling of the UV-riboflavin-cornea interactions, plus a clinical validation program, the team’s updated sub400 protocol now includes a distinctly higher fluence and 9 mW/cm² accelerated cross-linking intensity. This will allow for shorter customized sub400 protocol UV irradiation times for both doctors and patients.
Slit lamp CXL
In addition to their work on advancing CXL procedures, Prof. Hafezi told OSN that he and his team are exploring new avenues for the technology. For example, performing CXL procedures with the patient sitting upright at the slit lamp rather than lying down. To prove the validity of this approach, the team examined the depth of the demarcation line in 23 eyes that underwent cross-linking at the slit lamp and compared the results to the existing literature. Prof. Hafezi explained to OSN that the results showed “no difference in the depth of cross-linking effect.” This is an important finding that supports the concept that CXL at the slit lamp (in an office-based setting) is as effective as CXL performed in a laying position (typically in an operating theater).
Prof. Hafezi told OSN that through their work, they aim to improve the quality of care that patients receive and make CXL procedures faster and more convenient adding “We are always looking for ways to make our procedures better and more effective, and to provide the highest level of care to our patients.