Diabetic Retinopathies and their associated factors; a study in a tertiary care hospital in Karachi Pakistan Muhammad Tahir Rizwan Khan Supervisor: Prof. Akhtar Hussain The Faculty of Medicine, Institute of Health & Society, Department of Community Medicine, University of Oslo Co-Supervisor: Prof. Abdur Rasheed Khokar Professor & Head Departmemt of Ophthalmology, Unit II, Dow University Hospital Dow University of Health Sciences Thesis submitted as a part of the Master of Philosophy Degree in International Community Health May, 2014