The Light Transmittance Of Infected Corneas Containing Riboflavin Or Rose Bengal Under The Light Wavelength Of Uv-A Light Or Green Light

To investigate and compare light transmittance (LT) in uninfected and infected corneas containing riboflavin (rf) or rose bengal (rb) under UV-A light (365 nm) or green light (522nm) using an ex-vivo porcine cornea model.

Experimental study conducted in the Institute of Medical Microbiology, University of Zurich, and the Particle-Biology Interactions Laboratory, Empa.

A total of 162 ex-vivo porcine eyes were divided into nine groups, including three control groups, three groups infected with Staphylococcus aureus and three groups infected with Pseudomonas aeruginosa and cultured for 24 hours at 37°C and 5% CO2. Either 0.1% rf or 0.1% rb was applied to two uninfected, two S. aureus, and two P. aeruginosa infected groups, leaving the three remaining groups without chromophore. Corneal buttons were obtained and placed into 48-well plates. Corneal light absorbances were measured at light wavelengths of 365 nm and 522 nm by a spectrophotometer. LTs were calculated and compared. Results were corroborated with transmission electron microscopy (TEM).

Rf-saturated corneas infected by S. aureus or P. aeruginosa (LT = 1.18% ± 1.12 and 1.02% ± 1.05) exhibited 2.9-fold and 3.4-fold lower LTs than uninfected corneas (LT = 3.45% ± 2.00) (both p-values < 0.001). No LT difference was found between rb-saturated corneas infected by S. aureus or P. aeruginosa and uninfected corneas (LT = 0.01% ± 0.00) (both p-values = 0.08). TEM showed bacteria on corneal stroma borders and occasionally inside the stroma.

The LT of rf-saturated infected corneas is much lower compared to uninfected corneas, while rb-saturated corneas maintained consistently a low LT before and after infection. These findings indicate the potential to enhance PACK-CXL protocols by increasing irradiation fluence.