# The Potential of Visible and Far-Red to Near-Infrared Light in Glaucoma Neuroprotection
###### Abstract  
Alternative treatment strategies are necessary to reduce the severity of glaucoma, a group of eye conditions that progressively damage the optic nerve and impair vision. The aim of this review is to gain insight into potentially exploitable molecular mechanisms to slow down the death of retinal ganglion cells (RGCs), a fundamental element in the pathophysiology of all forms of glaucoma, and to stimulate adult optic nerve repair. For this purpose, we focus our analysis on both visible and far-red to near-infrared light photobiomodulation (PBM) as phototherapeutic agents, which were recently proposed in RGCs, and on the nerve lamina region neural progenitor cell (ONLR-NPC) niche. Both are suggested as potential strategies in glaucoma neuroprotection. We discuss the impact of beneficial molecular effects of PBM on both mitochondrial derangement and the alteration of ion fluxes that are considered important causes of RGC damage, as well as on the stimulation of progenitor cells. We suggest these are the most promising approaches to prevent excessive neuronal cell loss. We describe the experimental evidence supporting the validity of PBM therapy which, despite being a safe, non-invasive, inexpensive, and easy to administer procedure, has not yet been fully explored in the clinical practice of glaucoma treatment. glaucoma; photobiomodulation (PBM); visible and far-red to near-infrared (FR/NIR) light therapy; low-level laser therapy (LLLT); retinal ganglion cells (RGC); mitochondrial dysfunction; nerve lamina region neural progenitor cell (ONLR-NPC) niche +
Footnote †: journal: 2021  
familial glaucoma [4], which is relatively rare. Primary angle-closure glaucoma shows a higher incidence of blindness, even though it is less common than open-angle glaucoma [3]. The mechanisms defining glaucomatous neurodegeneration are not fully understood [5]. To delay or halt retinal ganglion cell (RGCs) death, different strategies, including surgery and topically pharmacological agents, have been proposed; these prolong visual function, lower IOP, and succeed in reducing the rate of progression in defined subjects. Nevertheless, some glaucomatous patients do not benefit significantly from such treatments [6]. Therefore, various substances have been proposed as add-ons. These include antioxidants, nitric oxide synthase inhibitors and NO-donating agents, adenosine receptor antagonists, Rho-pathway inhibitors, PI3K/Akt activators, purinergic ligands, ATP-sensitive potassium channel (KATP) channel activators, glutamate antagonists, neurotrophic factors, dopamine and serotonin receptors ligands, cannabinoid, non-glucocorticoid steroidal compounds, histone deacetylase inhibitors [6,7], and the use of stem cells and gene therapy [8]. As improvements need to be made to reduce the severity of glaucoma, alternative treatment strategies are necessary. As such, the aim of this review is to gain insight into the potentially exploitable molecular mechanisms that can slow down RGCs death. A major mechanism for such death was suggested to be mitochondrial dysfunction and its related oxidative stress; indeed, mitochondrial potentiation and preservation is actively studied together, with the stimulation of progenitor cells being the most promising approach to prevent excessive RGC loss. This review will discuss the impact of mitochondrial derangement and the alteration of ion fluxes as being among the causes of RGC damage. Red light usage has been proposed as a non-invasive procedure to protect the death of RGCs in several diseases such as glaucoma, suggesting a mitochondrial effect of red/near-infrared (R/NIR) phototherapy [9]. As such, we focused our attention on visible and far-red/near-infrared light photobiomodulation (PBM) as phototherapeutic agents in RGCs, as well as on the nerve lamina region neural progenitor cell (ONLR-NPC) niche, as strategies in glaucoma neuroprotection. We will highlight the multiple beneficial molecular effects of visible and near red (NR) phototherapy.