Described herein are an apparatus and range of techniques used to study the retinal vasculature near the fovea, a description of the need and rationale for noninvasive in vivo monitoring of the retinal vasculature, a presentation of theoretical and practical considerations which demonstrate that entoptic visualization of the smallest capillaries near the fovea is optimized by a small short wavelength source (1 mm or less) rotating at 3.5 Hz in a circular path (radius 2 mm) imaged in the plane of the eye's entrance pupil and a discussion of the feasibility of using these techniques as a research and clinical tool.