Macular neovascularization (MNV) is a major cause of central vision loss in eyes with pathologic myopia, which develops in about 10% of these eyes. Eyes with pathologic myopia tend to have a very thin choroid that’s difficult to measure, but around dilated choroidal veins (DCVs), the choroid tends to be relatively thicker. Researchers investigated a possible hemodynamic relationship between DCVs and MNV and found that MNV might be a vascular unit that consists in part of DCVs.

The study included 58 eyes of 57 patients (mean age 71) with myopic MNV. The researchers defined dilated choroidal veins as having a diameter two-times larger than adjacent veins. They used indocyanine green angiography and swept-source OCT to detect DCVs that crossed the subfoveal area.

Patients had a mean axial length of 29.3±1.8mm. In 17 eyes (29.3%), the researchers found dilated choroidal veins below or around the MNV. In eight of the 17 eyes, emissaries of the short posterior ciliary arteries were present at or around the MNV, and the short posterior ciliary artery was filled first or almost simultaneously with MNV filling, followed by laminar filling of DCVs. One eye had afferent arterioles from the short posterior ciliary arteries and efferent venules connected to DCVs, the researchers noted.

 “Sluggish venous flow in the DCVs as manifested by laminar flow was clearly observed in the indocyanine green angiography video recordings,” the researchers reported in their paper. “Swept-source OCT confirmed that the DCVs coursed beneath or adjacent to the MNV. The DCVs were seen in direct contact with the MNV through a defect of retinal pigment epithelium-Bruch membrane in 29.4% of the eyes. These results suggested that the colocalization of DCVs and MNV was not just a coincidence, but these two were most likely closely related. However, the prevalence of foveal DCVs in highly myopic eyes with and without MNV was not determined. Thus, it remains unclear whether the foveal DCVs were more common in the eyes with MNV than those without it.”

The study authors concluded that about 30% of eyes with myopia MNV have dilated choroidal veins below or around the MNV. “Our findings suggest that MNV might be a vascular unit consisting of short posterior ciliary arteries, afferent arterioles, efferent venules and DCVs,” they wrote in their paper. “It’s [also] possible that a chronic choroidal venous congestion in pathologic myopic eyes may be related to the development of a myopic MNV.”