Intraocular pressure (IOP) modifications in patients with acute central/hemicentral retinal vein occlusions (RVOs) consist in IOP reductions and increases. The IOP reduction is due to a transitional hyposecretory phase of the aqueous humor, that increases gradually until 3mo after the venous occlusion onset, and then finally disappears after month 4th. The IOP increases lead to the ocular hypertension and glaucoma. The possible pathogenetic correlations between ocular hypertension/glaucoma and acute central/hemicentral RVOs have been classified into three groups: 1) the venous occlusion precedes the ocular hypertension/glaucoma causing neovascular glaucoma and secondary angle-closure glaucoma without rubeosis; 2) the ocular hypertension and the glaucoma precede the venous occlusion and favor its appearance (ocular hypertension, primary angle-closure, primary angle-closure glaucoma, and open angle glaucomas); and 3) the venous occlusion and the ocular hypertension/glaucoma are mostly age dependent appearances due to common vascular and collagen alterations, lacking a causal connection between the 2 conditions.