Several optical techniques that investigate blood contained within the retinal vessels are available or under development. We present a mechanical model that simulates the optical properties of the eye, the retinal vessels, and the ocular fundus. A micropipette is chosen as the retinal vessel model, and a mechanical housing is constructed to simulate the eyeball. Spectralon is used to simulate the retinal layers. Filling the eye with fluid index matched to the glass pipette eliminates reflection and refraction effects from the pipette. An apparatus is constructed and used to set the oxygen, nitrogen, and carbon dioxide concentrations in whole human blood. These whole blood samples are pumped through the pipette at 34 μL/min. Measurements made in the model eye closely resemble measurements made in the human eye. This apparatus is useful for developing the science and testing the systems that optically investigate blood and blood flow in the large retinal vessels. © 2000 Society of Photo-Optical Instrumentation Engineers.