Dopaminergic System of the Eye and Its Role in Glaucoma Pathogenesis

Glaucoma is a multifaceted disease characterized by optic nerve damage and retinal ganglion cell (RGC) degeneration, leading to optic neuropathy and vision loss. Neurodegenerative processes in the retina underlie glaucoma pathogenesis. Elevated intraocular pressure (IOP) is a contributing factor in the development and progression of most types of glaucoma, making IOP reduction the standard treatment approach, while existing neuroprotective therapies remain largely ineffective. Dopaminergic system (DS) of the eye and its role in ocular pathology are insufficiently studied, yet available data suggest that DS is one of the most significant regulatory systems in the eye. It is widely represented in ocular structures and participates in regulation of visual function, circadian rhythms, blood circulation, and aqueous humor dynamics, as well as in eye development. Both IOP elevation and retinal ganglion cell neurodegeneration in glaucoma are critically influenced by an imbalance in the DS components. In the vertebrate retina, dopamine serves as the primary neurotransmitter and neuromodulator. It is also a precursor to sympathetic nervous system mediators – epinephrine and norepinephrine – expanding its role in physiological processes, including IOP regulation. This review presents recent and foundational studies on the presence of dopamine and its receptors in various ocular structures, their significance in normal eye function, mechanisms of involvement in neurodegenerative processes in glaucoma, and in IOP regulation. Based on analysis of the DS role in glaucoma pathogenesis, the prospects for developing antiglaucoma drugs for neuroprotection, IOP reduction, and combined mechanisms of action are discussed. Additionally, potential use of the analysis of DS components in the tear fluid as a non-invasive test for early diagnosis, prognosis, and therapeutic justification is considered.