A typical corneal cross-linking (CXL) procedure is performed in the operating room – but as Prof. Farhad Hafezi writes in Cataract and Refractive Surgery Today, this costs time and money.
CXL is a surgical technique, and like most surgical procedures, corneal cross-linking procedures are performed in an operating room (OR). ORs need to be booked in advance, require extensive cleaning and sterilization before every procedure to give the surgeon a sterile environment. For these reasons, corneal cross-linking procedures carry both an organizational overhead, as well as the cost burdens associated with using an OR.
But CXL not only strengthens the cornea; it also sterilizes it. Accordingly, Prof. Hafezi and his team made a simple proposal: perform CXL at the slit lamp (in the doctor’s office), not the OR. In the article, he explains the steps he had to take to demonstrate to the world that CXL at the slit lamp is not only safe and effective but also practical.
The questions people asked were threefold:
1. Is there a risk of corneal infection?
No, the UV light interacting with riboflavin produces reactive oxygen species. This not only cross-links (binds) the structural molecules in the cornea together, it also attacks and kills the cell walls and nucleic acids of pathogens, killing them (much like immune cells do). The cornea is left sterile at the end of the procedure, and antibiotics are given immediately afterward.
2. Isn’t the procedure too long to have a person sit at the slit lamp for all that time?
It is true that the classic “Dresden protocol” CXL protocol requires 30 minutes of illumination, which is a long time to be sat at the slit lamp. However, because of a phenomenon of “reciprocity”, if you triple the intensity of illumination, you can cut the duration to just 10 minutes – and it is still just as safe and effective as the original half-hour long protocol.
3. If people are sitting upright in a chair in the office, rather than lying down in the chair, does that mean that the riboflavin that is inside the cornea will settle to the bottom of the eye?
No. The experiments performed by Prof. Hafezi’s research team have shown no significant settling or shift in riboflavin concentration in the stroma, even after 1 hour of sitting upright after saturation.
There’s a second, great advantage to performing cross-linking procedures outside of the OR. Cross-linking’s sterilizing effect can be used to treat corneal infections, in a process called photoactivated chromophore for keratitis CXL (PACK-CXL). It’s less than ideal to bring an infection into an operating room, as it places a big burden on the staff to eradicate the pathological organism from the room afterward. But if CXL can be performed outside of the OR, either at the slit lamp or in a supine position, then this makes life easier. In the article, Prof. Hafezi explores the potential of PACK-CXL at the slit lamp to completely change how corneal infections, also known as “infectious keratitis”, are treated.