Inclusion Criteria:

1. Ages Eligible for Study: ≥ 18 Years
2. Ability to provide written informed consent and comply with study assessments for the full duration of the study
3. Diagnosis of diabetes mellitus (type 1 or 2). Any one of the following will be considered to be sufficient evidence that diabetes is present: Laboratory reports that prove DM of patient or current regular use of insulin for treatment of diabetes or current regular use of oral anti-hyperglycemic agent for the treatment of diabetes.
4. Clinical evidence of retinal thickening due to macular edema involving the center of the macula (can be associated with diabetic retinopathy)
5. Central diabetic macular edema present on clinical examination and OCT testing with central 1mm sub field thickness greater than 300 microns as measured on -OCT
6. Visual acuity score greater than or equal to 19 letters (20/400) and less than or equal to 73 letters (20/40) by the ETDRS/ Snellen chart visual acuity protocol
7. Media clarity, pupillary dilation and patient cooperation sufficient to allow OCT testing and retinal photography
8. Willingness and ability to undertake all scheduled visits and assessments

Exclusion Criteria:

1. Prior treatment with any Intravitreal drug, Bevacizumab, verteporfin or photodynamic therapy (except for extra foveal laser photocoagulation) in the study eye within past 3 months before study entry
2. Laser photocoagulation in the study eye within 1 month before study entry
3. Participation in another ocular investigation or trial simultaneously
4. Pregnancy (positive pregnancy test) or known to be pregnant; also pre-menopausal women not using adequate contraception.
5. Blood pressure > 160/100 mmHg (systolic above 160 or diastolic above 100) and Random Blood Sugar (RBS) ≥ 12 mmol/L and/ or HbA1c ≥ 7.5%
6. Evidence of vitreoretinal interface abnormality and optic nerve disease after ocular exam or OCT that may be contributing to the macular edema
7. Any concurrent intraocular condition in the study eye that could either require medical or surgical intervention during the study period or that could contribute to a loss of best corrected visual acuity over the study period (e.g. cataract that might decrease the vision by 3 or more lines, uncontrolled glaucoma, uveitis, previous corneal transplant etc.). The decision regarding exclusion is to be based on the opinion of the investigator.
8. An eye that, in the investigator's opinion, has no chance of improving in visual acuity following resolution of macular edema (e.g. presence of sub retinal fibrosis or geographic atrophy).
9. Presence of suspected ocular or periocular infections, another ocular condition that may affect the visual acuity or macular edema during the course of the study (uveitis, Irvine-Gas)
10. Vitreous hemorrhage preventing visualization of retina
11. History of vitreous surgery, cataract surgery, YAG capsulotomy in the study eye within last 3 months of enrolment
12. Visual acuity <20/400 in the fellow eye
13. Known hypersensitivity to Ranibizumab or any of the components of study medication
14. History of cerebral vascular accident or myocardial infarction within past 3 months.
15. Employees of Investigational sites, individuals directly involved with the conduct of the study or immediate family members thereof, prisoners, and persons who are legally institutionalized.
16. Current use of systemic medications known to be toxic to the lens, retina or optic nerve, including deferoxamine, chloroquine/ hydroxychloroquine, tamoxifen, phenothiazine, vigabatrin and ethambutol, and such medications will not be allowed during the study period.