When treating infectious keratitis, the use of PACK-CXL as an adjuvant therapy to standard of care (SOC) antimicrobial therapy improves matters, compared with SOC alone, is the take-home message from a study published this month in Cornea.
PACK-CXL is a well established method of treating corneal infections, and involves saturating the region of infection with riboflavin (vitamin B2) and irradiating the area with ultraviolet (UV) light. The UV light photoactivates the riboflavin, and causes the generation of reactive oxygen species (ROS), which go on to have a number of beneficial effects. First, ROS directly damage the cell membranes and nucleic acids of pathogens – a direct antimicrobial effect that is totally independent on conventional antimicrobial drugs. ROS also cross-link together tissue in the cornea, which through a process called steric hindrance, reduces the number of enzyme binding sites for pathogen-produced protein-digesting enzymes to act on. This is something that reduces the size of the ulcer, and therefore the eventual corneal scar size. If the ulcer, then the scar, resides in the centre of the patients’ cornea, minimising scar size could have a significant impact on the patient’s eventual quality of vision.
A multinational consortium of corneal specialists, spanning the ELZA Institute in Switzerland, Egypt, and Israel set out to perform a retrospective study that compared the effects of SOC treatment and PACK-CXL as an adjuvant to SOC treatment for corneal ulcers caused by a bacterial infection in 47 eyes from 47 patients, on the time it took for corneal ulcers to be successfully treated and the patients’ final visual acuity.
Patients (n=26) who received both PACK-CXL and SOC therapy did significantly better than patients (n=21) who received SOC therapy alone, in terms of best-corrected visual acuity, re-epithelialization time, and no dual-therapy patient required tectonic grafts to be performed, whereas one-third of the patients in the SOC therapy alone group did require these grafts.
The authors concluded that “In conclusion, we show that PACK-CXL is safe for use in bacterial keratitis cases. It also seems to add value in reducing healing time and improving final visual acuity while reducing the need for tectonic keratoplasty.”
Achiron A, Elhaddad O, Regev T, et al. Pack cross-linking as adjuvant therapy improves clinical outcomes in culture-confirmed bacterial keratitis. Cornea. Published online November 4, 2021.