Several factors prompt new approach to treating corneal diseases in patients.
This article was reviewed by Jose Gomes, MD, PhD
Antimicrobial resistance, epithelial toxicity resulting from frequently instilled fortified and toxic drugs, and lack of compliance with drug regimens are all problems associated with topical therapies.
These three factors cry out for a new approach to treating corneal diseases, and collagen crosslinking (CXL) may be a new strategy, according to Jose Gomes, MD, PhD, professor of ophthalmology, Cornea and External Disease Service, Paulista Medical School/Federal University of Sao Paulo, Brazil.
Photochemical CXL works by increasing the stiffness of the corneal tissue. Besides, CXL has the added benefit of a disinfectant effect that is achieved by combining ultraviolet A (UVA) plus riboflavin, he said.
Photo-activated chromophore for keratitis (PACK) CXL may be considered the next therapeutic step in cases of confirmed infectious keratitis in which atimicrobial resistance rears its head.
The technology has been used to treat non-infectious keratitis for years, and in 2016 started to be used to treat mild cases of infectious keratitis, Dr. Gomes pointed out.
In vitro and in vivo studies and clinical case series have reported the beneficial effects of PACK-CXL for infectious keratitis.
Dr. Gomes cited a pre-clinical study of the in vitro effect of riboflavin/UVA for treating bacterial and fungal isolates that reported that some gram-positive and gram-negative bacteria but not fungi are susceptible to CXL (Martins et al. Invest Ophthalmol Vis Sci. 2008;49:3402-8).
However, previous treatment with amphotericin B allowed riboflavin/UVA effectiveness against Candida, Fusarium, and Aspergillus (Sauer et al. Invest Ophthalmol Vis Sci. 2010;51:3950-3953). The in vivo results of PACK-CXL also showed beneficial results in an animal model of fungal keratitis (Özdemir et al. Acta Ophthalmol. 2019;97:e91-e96).
In clinical studies, case series have reported that CXL helps in managing advanced microbial keratitis refractory to topical medical therapy (Shetty et al. Br J Ophthalmol. 2014;98:1033-5).
A combination of medical therapy and CXL or CXL alone can be efficacious, Dr. Gomes said. He also described a case of Pseudomonas keratitis treated with PACK-CXL at the Paulista Medical School, Sao Paulo. The case resolved well by day 18 after treatment with CXL.
CXL also was shown to reduce the time to resolution of suppurative fungal corneal ulcers, as reported recently (Basaiawmoit et al. Cornea. 2018;37:1376-8).
“We in Brazil also found that some cases of fusarium keratitis responded well to CXL, especially when the fungal infection was more superficial in the corneal tissue,” Dr. Gomes said.