Diabetic retinopathy is a major complication of diabetes and the biggest cause of blindness. The goal of the research is to investigate the role of nitric oxide (NO) as a neural modulator from normal and diabetic retinas by using electrophysiological recordings and quantitative signal analysis and by integrating retinal blood flow and retinal cellular function studies. Studies have suggested that NO may be both a neural modulator and a blood flow regulator in the eye under normal and diseased states. The limiting factor has been scarcity of quantitative studies that address both retinal function and retinal blood flow. Current information about retinal blood flow is inconsistent due to variations in measuring techniques and data analysis; hence, it is difficult to interpret results of NO studies. The significance of our work is that it will fill the gaps in our understanding of NO and its role as a neurotransmitter and blood flow controller in an in vivo model, including the diabetic state.