IN-VIVO EVALUATION OF LEUKOCYTE DYNAMICS IN RETINAL ISCHEMIA-REPERFUSION INJURY

PURPOSE. TO evaluate quantitatively leukocyte dynamics in vivo in the rat retinal microcirculation during ischemia reperfusion injury with t he use of acridine orange digital fluorography. METHODS. Retinal ische mia was induced in anesthetized pigmented rats by a temporary Ligation of the optic nerve. After 60 minutes of ischemia, leukocyte behavior in the retinal microcirculation was evaluated, with acridine orange di gital fluorography-consisting of a scanning laser ophthalmoscope and t he fluorescent nuclear dye, acridine orange-during reperfusion at 1, 2 , 4, 6, 12, 24, 48, 96, and 168 hours. The obtained images were record ed on videotape and analyzed with a computer-assisted image analysis s ystem. RESULTS. Rolling leukocytes along the major retinal veins were observed in treated rats during the reperfusion period; no rolling leu kocytes were observed in the control rats. The number of rolling leuko cytes gradually increased and peaked at 102 +/- 40 cells/minute 12 hou rs after reperfusion; few rolling leukocytes were observed at 96 hours . The velocity of rolling leukocytes at 12 hours (19.1 +/- 3.5 mu m/se cond; P < 0.05) was significantly lower than that at the other three t imes. No rolling leukocytes were observed along the arterial walls thr oughout the experiments. The number of accumulated leukocytes increase d as time elapsed, peaked at 931 +/- 187 cells/mm(2) 24 hours after re perfusion, and decreased thereafter. CONCLUSIONS. Leukocyte dynamics i n the retinal microcirculation can be quantitatively evaluated during ischemia reperfusion injury.