PULSATILE FILLING OF DILATED CHOROIDAL VESSELS IN MACULAR WATERSHED ZONES.

Purpose: To describe pulsatile filling of dilated choroidal veins in the watershed zones and propose an alteration in choroidal perfusion pressure.

Methods: Retrospective review of original and digital subtraction indocyanine green angiography.

Results: We observed pulsating blood flow within choroidal vein segments in the posterior pole in 14 eyes (diagnosis of polypoidal choroidal vasculopathy, central serous chorioretinopathy, or neovascular age-related macular degeneration). Pulsating dye front was observed in single or multiple large choroidal vein(s) in a location that is ordinarily a watershed zone between the segmental areas of venous drainage, and vessels proximal and distal were often dilated. The pulsatile venous segments filled more slowly than the neighboring veins. In digital subtraction indocyanine green angiography, the dye front advanced in an incremental fashion or oscillated in a back-and-forth manner during several cardiac cycles during the filling of these larger choroidal veins. With indocyanine green angiography, we observed dilated choroidal veins that violated the macula watershed zone, localized bulbous dilations, and arteriole-over-vein crossings with apparent compression.

Conclusion: These novel observations suggest the pressure gradient for flow in the affected veins varied from low gradients when the filling was slow to high gradients when the filling was faster. The vessels violated the physiological watershed zone and seem to function as anastomoses between the ordinarily segmented venous drainage of the choroid. The dilated segments may result in pooling of venous blood as part of venous outflow abnormalities that may be operative in these diseases.