Conclusion The hemodynamic features of central retinal arteries in patients with retinal vein occlusion are low blood flow velocity, low vessel filling intensity and poor distal tissue blood filling.

Objective To observe the changes of microcirculation of central retinal vessel system of patients with retinal vein occlusion.

So if you are measuring brachial blood pressure which is a much smaller tube than the central large artery and the more pliable the vessel is the less likely there is to be a difference.