Prolonged Photobiomodulation with Near-Infrared Light mitigates incipient retinal deterioration in a Mouse Model of Type 2 Diabetes

Diabetic retinopathy is a prevalent complication of type 2 diabetes mellitus, characterized by progressive damage to retinal structure and function. Photobiomodulation therapy, using near-infrared light, has been proposed as a non-invasive intervention to mitigate retinal damage, but has been tested generally with short-term stimuli. This study aimed to evaluate the effects of prolonged photobiomodulation on retinal structure and function in a type 2 diabetes mouse model. Transgenic LepRdb/J (db/db) mice and their heterozygous controls were exposed to photobiomodulation therapy via LED devices emitting 654 nm light for 12 hours daily over ten weeks. Retinal function was evaluated by flash electro-retinography, while structural changes were assessed through histology and immuno-histochemistry to detect astro- and microgliosis. At 33 weeks of age, db/db mice were obese and severely diabetic, but exhibited only incipient indicators of retinal deterioration. Electroretinogram b-wave peak latencies were prolonged at intermediate flash intensities, while the outer plexiform layer displayed significantly elevated IBA1 expression. Photo-biomodulation therapy prevented these two markers of early retinal deterioration, but had no effect on other morphological and functional parameters. Photobiomodulation is well-tolerated and maintains potential as a complementary treatment option for diabetic retinopathy, but requires further optimization of therapeutic settings and combinatory treatment approaches.