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PACK-CXL yields ‘good response’ in antibiotic-resistant infectious keratitis
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PACK-CXL proved effective as a treatment for infectious keratitis in a series of patients with large, central corneal ulcers not responding to antimicrobial treatment.
PACK, which stands for photoactivated chromophore for keratitis, consists of the application of corneal cross-linking (CXL) to cases with severe infectious keratitis. The study included 18 consecutive eyes of 18 patients with severe infectious keratitis, previously and unsuccessfully treated with fortified antibiotic therapy.
The procedure was performed in the OR after the application of topical anesthesia. The epithelium was scraped over the affected area, and riboflavin 0.1% was instilled every 2 minutes for 30 minutes. UVA irradiation was performed for 10 minutes with an energy fluence of 9 mW/cm2, still under instillation of riboflavin every 2 minutes. After the procedure, fortified antibiotic treatment was resumed.
Corrected distance visual acuity did not significantly improve after PACK-CXL, likely due to the size and location of the ulcers, ranging from 1 mm to 5 mm both in length and width and mostly centrally located. However, only one of the patients required penetrating keratoplasty due to corneal perforation.
“We believe that this low rate may be attributed to good response to the CXL treatment, which stopped the melting procedure,” the authors wrote.
There is still no consensus on how early PACK-CXL should be performed. The patients in this study were treated on average 10 days after diagnosis when a poor response to antibiotics was shown, the ulcer was increasing in size, and the cornea was thinning or melting. The authors observed that the only patient who underwent PK was treated 25 days after diagnosis and that the patients treated earlier responded better.
“Therefore, we assume that it is better to perform CXL as early as possible,” they said. – by Michela Cimberle
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Farhad Hafezi, MD, PhD
The study both supports and reinforces previous findings (and those of our own study group and collaborators) that PACK-CXL can successfully be used as an adjuvant to antibiotics to treat advanced, therapy-resistant bacterial keratitis — including melting ulcers.
There has been some debate regarding the best time to commence PACK-CXL in corneal ulcers. An example of a debate would be about how much time you wait to see if antibiotic therapy works before commencing PACK-CXL. Currently, the answer is still yet to be determined. This study shows that waiting an average of 10 days before performing PACK-CXL (in addition to antibiotic therapy) was successful in treating these severe, melting central ulcers. Additionally, after a mean of almost 18 months of follow-up, there was no change in corrected distance visual acuity. The authors themselves note that additional studies are needed to determine the optimal time point at which PACK-CXL should be used to treat infectious keratitis, and we are happy to see that these results are in line with what we are seeing in our own multicenter clinical trial.
It is worth noting that even though PACK-CXL was only used in the most advanced cases in their study, their results still show a favorable clinical outcome. These results raise the question: If PACK-CXL can successfully treat advanced keratitis as an adjuvant to antibiotics, might it also work as a first-line treatment, sparing the use of antibiotics in an era in which antibiotic resistance is increasingly a worry?
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