 The purpose of this study is to evaluate topographic features of the posterior pole of the eye in normal subjects as well as in subjects with diabetes mellitus but without diabetic retinopathy DR using optical coherence tomography OCT. The investigators proposal is a novel study to determine retinal volume of normal and diabetic subjects without DR. Specifically, the investigators will establish a standardized reference range for retinal thickness and volume that will provide standards for OCT analysis of different clinical trials for retinal diseases. 