Anatomical study revealed that vitreous base is attached to the macula and in the region of the optic disc, that is why biochemical changes- inflamm. atory agents, prostaglandin, etc. after non-complicated and more prominent in complicated surgery cases causes macular edema in cystoid fasion, which is confirmed by fluorescein angiography of retina. Really anatomy is involved in this process.

great question Maimone..Vitreous traction could be one of the contributory cause as mentioned by Marianne.. Muller cells at the level of outer nuclear layer are responsible for phagocytosis and cleaning up of mess in retina. The density and enzymatic function of muller cells is low at foveal region(density keeps on increasing as u move to periphery). That is the region of deposition of either fluid or exudates at foveal region. This hold true for all macular pathology with exudation. Hope this helps

I think that two reasons are responsible: anatomical and inflammation secondary to the trauma during phacoemulsification. Marianne wrote about anatomical.The tight connection between vitreous base and macula are "responsible" why in macula. In the case of trauma during surgery on the anterior eye segment(not only cataract surgery), releasing of phospholipase A2 leads to the production of arachidonic acid which breaks the lipids in cellular membarene. In that case cyclooxygenase converts some lipids into prostaglandins who directly mediate vascular lekeage and beakdown of blood-retinal barrier together with leukotriens.

The transudated or exudated fluid to the retina is drained by the RPE and the venous system in the whole retina. But in the fovea the RPE is the only drainer as there is no venous drainage.