Exploring dose-dependent outcomes of photobiomodulation with two infrared wavelengths applied to injured Drosophila retinae.

Abstract

The use of photobiomodulation as a therapeutic tool has attracted copious research over the past several years. However, given the many variables involved in the design of a treatment regimen, such as wavelength, irradiance, exposure duration, number of treatments, and total treatment period, many studies are inherently not comparable as they often differ in at least one of these parameters. Here, we assess dose and wavelength dependency of photobiomodulation in a model of light-induced retinal damage in Drosophila melanogaster. Light-damaged Drosophila were exposed to either 850 or 950 nm light twice per day over a 10-day period with a total dose of 1, 4, 11, or 20 J/cm2. Treatment with 850 nm light was found to be generally more effective in promoting recovery of photoreceptor function, with higher doses being more efficacious. Treatment with 950 nm light, regardless of dose, did not result in improved photoreceptor function; however, a slightly increased photoreceptor response was observed upon treatment with a fluence of 11 J/cm2 when compared to other doses of the same wavelength. We also observed elevated ATP levels in 850 nm treated flies and higher doses of 950 nm light. Our findings suggest that increased ATP did not directly correlate with photoreceptor recovery, implying that multiple processes are involved, the nature of which warrant further investigation.