New patterns of retinal collateral circulation are exposed by a retinal functional imager (RFI)

Aims: To describe different patterns of retinal collateral circulation observed in normal subjects and in patients with a variety of ocular diseases during studies with the retinal functional imager (RFI). Methods: Normal subjects and patients with various ocular diseases underwent retinal blood flow imaging using the retinal functional imager. Results: Twenty-eight eyes of 21 patients constituted the study population (eight eyes of six normal subjects and 20 eyes of 15 patients with different ocular diseases). Four patterns of retinal collateral circulation have been recognised: (1) looped collateral pattern-this arterovenous anastomotic vessel is characterised by a link between the endings of the adjacent artery and vein, and has an appearance of a loop; (2) vertical collateral pattern-this anastomotic vessel is characterised by a connection between superior and inferior vascular systems (arterial or venous), and in its course this collateral vessel crosses the horizontal raphe; (3) H-shaped collateral pattern-this arterovenous anastomotic vessel is characterised by a connection between two adjacent vessels (artery and vein), but, unlike anastomotic vessel of the looped'' pattern, this vessel connects the middle parts of the vessels and not the endings of these vessels; (4) cilioretinal-retinal collateral pattern. This anastomotic vessel is characterised by a link between the cilioretinal artery and retinal arterial circulation. Conclusions: The findings of this study shed a different light on the retinal circulation and have demonstrated new patterns of retinal collateral circulation evident from RFI imaging. These patterns appear to be present in normal subjects as well as in patients with various ocular diseases.