This invention relates to the treatment of macular edema. Macular edema is the main cause of vision loss during diabetic macular edema, wet AMD (Age Related Macular Degeneration), retinal vein occlusion and chronic intraocular inflammation. Currently, beyond photocoagulation by laser irradiation, two types of drugs are used, protein molecules that neutralize VEGF family members and glucocorticoids, with different mechanisms of action, but targeting one single symptom: macular edema. The inventors have now found that macular edema may be treated by increasing the oncotic pressure of the vitreous. According to the inventors' understanding, causing an increase in the oncotic pressure of the vitreous induces a liquid flow from the interstitial water accumulated in the retina tissue to the vitreous compartment, so as to reduce or stop macular edema. Increasing the oncotic pressure of the vitreous is preferably performed by intravitreal injection of an oncotic pressure-increasing macromolecule, which macromolecule may be selected in a group comprising protein or non-protein macromolecules, such as albumin, gelatin, alpha2 macroglobulin, fibrinogen, haptoglobin multimers, beta lipoproteins and antibodies, as well as dextran and hydroxyethyl starch.