24 Week Study to Compare Systemic VEGF-levels of Ranibizumab and Aflibercept in DME.

Inclusion Criteria: * Type 1 or Type 2 diabetes mellitus * Visual impairment due to DME * BCVA of 78 to 24 (20/32-20/320) ETDRS letters Exclusion Criteria: * Stroke or myocardial infarction less than 3 months prior to screening. * Presence of uncontrolled systolic blood pressure or diastolic blood pressure * Renal failure requiring dialysis or renal transplant or renal insufficiency * Untreated diabetes mellitus * Use of any systemic anti-VEGF drugs within 6 months prior to screening. * Use of systemic or inhaled corticosteroids for at least 30 consecutive days within 3 months prior to screening. * Women who are pregnant or breast feeding or who are menstruating and capable of becoming pregnant\* and not practicing a medically approved method of contraception For either eye: * Any active periocular or ocular infection or inflammation * Uncontrolled glaucoma * Neovascularization of the iris or neovascular glaucoma * History of treatment with any anti-angiogenic drugs For study eye: * Atrophy or fibrosis involving the center of the fovea at the time of screening or baseline. * Cataract (if causing significant visual impairment), planned cataract surgery during the study period, vitrectomy, aphakia, glaucoma surgery, severe vitreous hemorrhage, rhegm * Irreversible structural damage within 0.5 disc diameter of the center of the macula * Panretinal laser photocoagulation within 6 months prior to randomization. * Focal/grid laser photocoagulation within 3 months prior to randomization. * Any intraocular procedure (including cataract surgery, Yttrium-Aluminum-Garnet capsulotomy) within 3 months prior to baseline or anticipated within the next 6 months following * Topical ocular corticosteroids administered for at least 30 consecutive days within 3 months prior to screening. * Application of intravitreal corticosteroids in vitreous within 6 months prior to screening. Prior application of fluocinolonacetonid releasing implant in vitreous within 36 months prior to screening. For fellow eye \- Retinal or choroidal neovascularization or macula edema of any cause Other protocol-defined inclusion/exclusion criteria may apply.