Glaucoma is a multifactorial neurodegenerative disease of the optic nerve currently considered a severe health problem because of its high prevalence, being the primary cause of irreversible blindness worldwide. The most common type corresponds to Primary Open-Angle Glaucoma (POAG). Glaucoma produces, among other alterations, a progressive loss of Retinal Ganglion Cells (RGC) and its axons, key to generate the action potential that reaches the visual cortex to create the visual image. It indicates a Visual Field (VF) loss whose main feature is to be painless, and this makes early detection difficult, causing a late diagnosis and delaying a timely treatment indication that slows down its progression. Intrinsically photosensitive Retinal Ganglion Cells (ipRGCs), which represent a subgroup of RGCs being sensitive to damage, are characterized by reacting to short-wave light stimulation close to 480 nm and among their non-visual function, the role in the generation of the pupillary reflex stands out. Currently, the sensitivity of clinical trials correlates to RGC damage, however the need for an early damage biomarker is still relevant. It is an urgent task to create new diagnostic approaches to detect an early stage of glaucoma in a prompt, quick, and economical manner. We suggest evaluating the pupillary response to chromatic light as a potential biomarker of disease, its diagnostic benefit, and its cost-effectiveness in clinical practice to reduce irreversible damage caused by glaucoma.

Amblyopia is the interocular visual acuity difference of two lines or more with best correction in both eyes. Ocular occlusion therapy depends on neuroplasticity, and thus is effective in children but not in adult with later diagnoses. Transcranial Direct Current Stimulation (tDCS) is suggested to increase neuroplasticity. To determine if combined therapy of bilateral tDCS and ocular occlusion improves visual function in adults with amblyopia, we conducted a double blind randomized, controlled pilot trial in volunteers with amblyopia (ClinicalTrials.gov Identifier: NCT05016830). While applying ocular occlusion and performing a reading task, participants received sham bilateral tDCS or bilateral tDCS. Visual function and visual evoked potential were evaluated immediately after. 12 volunteers with amblyopia were randomized, 2 were excluded after misdiagnosis confirmation. A significant increase in visual acuity was observed after stimulation in the bilateral group (n = 5) versus the sham group (n = 5) along with a significant increase in visual evoked potentials amplitude in the amblyopic eye response. No significant changes were observed in stereopsis and contrast sensitivity. No volunteer reported any harm derived from the intervention. Our results suggest that bilateral tDCS might improve visual acuity in amblyopic adults through increasing neuroplasticity, which allows the therapeutic effect of ocular occlusion.