Diabetic retinopathy (DR) is one of the most common causes of blindness worldwide. It is a progressive disease and its detection in early phases is very crucial for visional outcomes. miRNA of exosomes has been recently considered as a potential circulating marker of oculopathy, including age-related macular degeneration and uveal melanoma. Therefore, the primary objective of this study is to evaluate whether the serum exosomal miRNA could be prospective prognosis biomarker to investigate the initiation and development of DR. This case-control study is planned to include diabetic patients, and patients without DR, which serve as controls. Other participants will be divided into four groups by different DR stages according to the guideline from AAO. Information and samples of all trial participants will be collected at the inception of the study, including basic information, medical history, serum samples, and several ophthalmologic examinations. Then these information and examinations will be collected at regular intervals: every 12 months until 5 years. Different statistical methods will be used to identify significant associations between DR progression and different exosomal miRNA. We hypothesis that there could exist alert level of exosomal miRNAs which indicate the onset and development of DR in diabetic patients. Moreover, the selected exosomal miRNAs, being considered together with other information including medical history, blood indicators and ophthalmologic examinations, to be chosen-optimized as a prognostic model for DR, which may help predicting high risk groups of DR and those with poor prognosis. Based on clinical trial data, we will further discuss about possible roles of identified miRNA of exosomes in the pathogenesis of DR.