Singlet oxygen formation during accelerated and hyperaccelerated corneal cross-linking: in vitro study

To evaluate the singlet oxygen (¹O₂) production of oxygen assisted %0.1 riboflavin and ultraviolet-A (UVA) crosslinking therapy (with and without oxygen assistance), in combination with standard, accelerated and hyper-accelerated procedures via an important quantitive marker of ¹O₂ which is the photo-oxidation of 1,3 diphenylisobenzofuran (DPBF).

%0.1 riboflavin-containing wells were irradiated with UVA light (365-nm wavelength) with or without 2-4-6-8 L/min oxygen flow assistance. Measurements of decrease in absorbance of DPBF were made in 30 mW (hyper-accelerated), 9 mW (accelerated), and 3 mW UV-A (standard) applications, and with additional 2-4-6-8 L/min oxygen flow in 30 mW and 2 L/min oxygen flow in 9 mW. A total of 8 different UV-A irradiance with and without oxygen supplementation groups were formed.

2 L/min oxygen assisted accelerated UV-A irradiance group has shown a greater decrease in DPBF absorbance compared to Dresden protocol. (p = 0.014) Also, Dresden protocol has shown a greater decrease in DPBF compared to all groups except accelerated crosslinking with 2 L/min oxygen. (p < 0.001) Oxygen assisted hyper-accelerated crosslinking groups were showed greater reduction in DPBF absorbance compared to standard crosslinking without oxygen groups. (p < 0.001).

Oxygen supplementation may increase the singlet oxygen generation to the similar levels of Dresden Protocol's in accelerated group. Also, more singlet oxygen generation with oxygen supplementation compared to standard UV-A application might be considered to be promising in terms of shortening the crosslinking therapy.