Noninvasive 11.7-T Magnetic Resonance Spectroscopy and Imaging Reveals Retinal Metabolic Alterations Induced by Blue...

The eye is a complex structure, with multiple systems involved in focusing and detecting light. Among them, the retina, an integral component of the central nervous system, is considered the most vital and exhibits the highest metabolic activity among all tissues in the human body. It interacts with light, and excessive exposure, especially to blue light, is prone to produce degeneration, mainly through oxidative reactions. This mechanism is involved in age-related macular degeneration or diabetic retinopathy. Animal research is important, considering the high prevalence of these diseases; yet noninvasive procedures involving this research are lacking so far. Our objective was to apply an animal model of oxidative stress and monitor the metabolic changes using 11.7-T ¹H-magnetic resonance spectroscopy (¹H-MRS). We exposed adult rats to high intensity blue light, at 440 nm (6000 lx) and investigated retinal metabolic changes up to 48 h post exposure. The acquired spectrum highlighted the presence of several essential retinal metabolites, including lipids (alkyl chain CH₂), lactate, N-acetylaspartate (NAA), glutamate (Glu), choline (Cho), taurine (Tau), creatine (Cre), and glucose (Glc). Blue light induced specific changes, relatable to oxidative stress, and ¹H-MRS allowed us to follow the dynamic metabolic changes post exposure. This is the first in vivo spectroscopic study of the retinal tissue in which no animals were sacrificed. To validate the in vivo metabolite assignments, localized ex vivo ¹H-MRS was performed on eyes from separate animals that had not been exposed to blue light.