Near infrared spectroscopy reveals instability in retinal mitochondrial metabolism and haemodynamics with blue light exposure at environmental levels.

Blue light (~400-470 nm) is considered potentially detrimental to the retina but is present in natural environmental light. Mitochondrial density is highest in the retina, and they exhibit a prominent optical absorption around 420 nm arising from the Soret band of their porphyrins, including in cytochrome-c-oxidase in their respiratory chain. We examine the impact of continuous 420 nm at environmental energy levels on retinal mitochondrial metabolism and haemodynamics in vivo in real time using broadband near-infrared spectroscopy. One hour environmental exposure to 420 nm induces significant metabolic instability in retinal mitochondria and blood signals, which continues for up to 1 h post blue exposure. Porphyrins are important in mitochondrial adenosine triphosphate (ATP) production and cytochrome-c-oxidase is a key part of the electron transport chain through which this is achieved. Hence, environmental 420 nm likely restricts respiration and ATP production that may impact on retinal function.