Step 1: The clue is the time link - a glaucoma named for appearing around the hundredth day after a vascular ocular event.
Step 2: Following an ischaemic central retinal vein occlusion, blood backs up, the retina becomes hypoxic, and repeated haemorrhages occur.
Step 3: The ischaemic retina releases angiogenic factors that grow new vessels on the iris and in the drainage angle; these vessels and the fibrovascular membrane choke aqueous outflow and the pressure climbs.
Step 4: Because this rubeotic glaucoma typically emerges about three months after the occlusion, the originating condition is CRVO.
\[\boxed{\text{Central retinal vein occlusion (CRVO)}}\]