The characteristics of fundus microvascular alterations in the course of glaucoma: a narrative review

BACKGROUND AND OBJECTIVE: As the vascular theory has led many researchers to focus on vascular dysfunction in the pathogenesis of glaucoma, a better understanding of ocular microcirculation would be of great significance. The emergence of optical coherence tomography angiography (OCTA) has shed light on the various fundus microvascular changes that occur in glaucoma, thus providing ample evidence in the role of microvascular dysfunction in glaucoma. The aim of this review is to provide an overview of the retinal and choroidal microvascular alterations that occur in glaucoma and to address the role of microvascular alterations in the pathogenesis, diagnosis, prognosis, and treatment of glaucoma. METHODS: The literature regarding fundus microvascular alterations in glaucoma and after glaucoma treatment, including alterations of vascular perfusion and vascular reactivity, was broadly researched using PubMed and Web of Science databases. The endothelium involvements during the glaucoma course were also searched in the databases broadly. KEY CONTENT AND FINDINGS: Previous OCTA studies show vessel density (VD) decreases in the retinal macular and peripapillary regions and choroidal microvascular dropout. Such microvascular alterations are correlated with structural and functional defects and have potential value for the early diagnosis and prognosis of glaucoma. Retinal microvascular autoregulation is also impaired in glaucomatous eyes. Furthermore, various studies have demonstrated the role of the vascular endothelium in glaucoma. Different topical medications and surgical interventions have been shown to have an impact on microvasculature in glaucoma, and animal experiments have indicated the endothelial system may be a new target in glaucoma treatment. CONCLUSIONS: Ample evidence proved the involvement of retinal and choroidal microvascular structural and functional changes in the course of glaucoma. This review makes a novel contribution to the literature by summarizing the microvascular alterations in glaucoma eyes and the microvascular changes after topical or surgical treatments.