The purpose of this study is to evaluate the proportion of patients with a 10 letters gain on Best Corrected Visual Acuity (BCVA) at 6 months in current medical practice.

Inclusion Criteria:

• Male or female patients >18 years of age who have signed an informed consent
• Patients with Type 1 or Type 2 diabetes mellitus (according to ADA or WHO guidelines) with HbA1c not more than 10.0% at screening (Visit 1). Patients should be on diet, exercise, and/or pharmacological treatment for diabetes.
• Patients with visual impairment due to focal or diffuse DME in at least one eye
• Central Retinal thickness on OCT ≥ 250 microns in the central subfield
• BCVA score between 78 and 39 letters, inclusively, using ETDRS-like visual acuity testing charts at a testing distance of 4 meters (approximate Snellen equivalent of 20/32 to 20/160)
• Decrease in vision is due to DME and not due to other causes, in the opinion of the investigator
• Medication for the management of diabetes must have been stable within 3 months prior to randomization and is expected to remain stable during the course of the study.

Exclusion Criteria:

Ocular concomitant conditions/ diseases

• Concomitant conditions in the study eye which could, in the opinion of the investigator, prevent the improvement of visual acuity on study treatment
• Active intraocular inflammation (grade trace or above) in either eye
• Any active infection (e.g. conjunctivitis, keratitis, scleritis, uveitis, endophthalmitis) in either eye
• History of uveitis in either eye Systemic conditions or treatments
• Active systemic infection
• History of stroke < 3 months
• Renal failure requiring dialysis or renal transplant OR renal insufficiency with creatinine levels > 2.0 mg/dl
• Untreated diabetes mellitus
• Blood pressure systolic > 160 mmHg and diastolic > 100 mmHg
• Untreated hypertension
• Known hypersensitivity to ranibizumab or any component of the ranibizumab formulation Others
• Women of childbearing potential not using the contraception method(s) specified in this study (specify), as well as women who are breastfeeding

Other protocol-defined inclusion/exclusion criteria may apply