Various HCT levels were obtained by mixing extracted RBCs with porcine plasma using ethylenediamine tetraacetic acid (EDTA) as an anticoagulant (Animal Technologies, Inc., Tyler, Texas). Different suspensions of normal RBCs, artificially aggregated with dextran, were prepared. RBCs were resuspended in plasma of dextran 500 (Dx500, average molecular mass ; Sigma, United State) at HCTs of 20, 40, and 60%. A plasma dextran concentration of 2% in weight/volume (w/v) was used to induce moderate RBC aggregation. All OCT measurements were performed just after RBC suspensions were prepared and pumped through a round glass capillary tube with a inner diameter (VitroCom Inc., Mountain Lakes, New Jersey) at a Doppler angle of . A programmable syringe pump (Harvard Apparatus, Holliston, Massachusetts) was used to make the blood flow with an approximately constant speed at a rate of , corresponding to an average flow velocity of within the glass capillary. The flow rate simulates the real values within major human retinal vessels with diameters . OCT “M-scans” (a single A-line repeatedly acquired in time without transverse scanning) were performed. One thousand and twenty-four OCT A-scans were averaged for each data set. Triplicate samples were prepared and measured for each HCT. All final results of SD values for both normal and aggregated blood were means of triplicate experiments. A paired test statistical analysis was applied for the differences in SD between the control group (without dextran) and the treated group (with dextran). For all tests, a level of 0.05 was chosen as a significant level.