Visualization and flow of platelets and leukocytes in vivo in rat retinal and choroidal vessels.

PURPOSE

To directly visualize the flow of leukocytes in choroidal vessels and the flow of platelets in retinal vessels in a rat without incision by fluorescein leukocyte angiography (FLA) using a scanning laser ophthalmoscope (SLO).

METHODS

Blood was withdrawn from a tail vein of a Sprague-Dawley rat with a tuberculin syringe traced with sodium heparin and mixed with sodium fluorescein. The fluorescent plasma layer was diluted with saline solution, centrifuged and then the overlying plasma discarded. The remaining cell suspension was diluted with saline to create the original hematocrit, then infused into the vein of the same rat while performing fluorescein angiography with an SLO. The angiographic image was recorded on a videotape using time-lapsed photography.

RESULTS

Fluorescent platelets were detected and the flow within the retinal vessels traced over time. Fluorescent leukocytes in the choroidal vessels were also detected and the flow of a leukocyte was traced and its relative velocities were plotted against the time sequence. The relative size and fluorescence intensities of the platelets and leukocytes in the angiographic image corresponded well with the smear of the blood preparation.

CONCLUSIONS

FLA using an SLO can be used to detect the flow of platelets in the retinal vessels and the flow of leukocytes in the choroidal vessels in the experimental rat eye model.