Age‐related macular degeneration: hemodynamic changes

Purpose Metabolic changes of the RPE associated to the dysfunction of choriocapillaries(CC)/RPE complex may induces the AMD‐related changes. Additional vascular changes in the choroid potentially have deleterious effects on the RPE. Methods Quantification of CC number and lumen diameters in cross sections and alkaline phosphatase (APase) flat‐embedding technique, expressing high constitutive APase activity in choriocapillaris and choroidal veins on human RPE/Bruch’s Membrane/CC complex, significantly contributed to the analysis of the choroidal vasculature. Laser Doppler flowmetry (LDF) data provided additional information on the assessment of hemodynamic changes in AMD. Results Choroidal vascular density reduction and significant vasoconstriction of the choriocapillaries, occurs during the evolution of AMD. In eyes with geographic atrophy, the RPE degenerates first while CC loss is secondary to RPE degeneration. In eyes with exudative AMD, degeneration of the CC layer occurs while RPE is still functional. LDF data indicated choroidal blood flow decrease according to age and the degree of severity of AMD; the decrease in flow preceding the formation of choroidal CNV, strongly suggest that these changes may have a role in the development of CNV. As a result of vascular dysfunction, the choroidal blood flow is dysregulated in patients with neovascular AMD. The choroidal watershed zone (WZ) courses through the fovea more often in patients suffering from AMD than in age‐matched controls, particularly in the presence of CNV. Choroidal neovascularisation usually arises within these WZ. Conclusion The role of choroidal ischemia in the pathophysiology of AMD is supported by the observed choroidal microcirculation anatomical and fucntional abnormalities.