ALTERATIONS OF RETINAL MICROCIRCULATION IN RESPONSE TO SCATTER PHOTOCOAGULATION

PURPOSE. TO perform acridine orange digital fluorography on rats after scatter photocoagulation to investigate alterations of retinal microc irculation at the capillary level, the authors used leukocyte dynamics as a parameter. METHODS. Twenty-five pigmented rats (Long-Evans) were studied. Argon laser photocoagulation, extending 6 disc diameters fro m the optic disc, was delivered to one half of the retina, and the oth er half was untreated. The total number of bums was 200 +/- 10. Leukoc yte hemodynamics in retinal microcirculation were evaluated 4, 7, 14, and 28 days after photocoagulation by acridine orange digital fluorogr aphy. The fundus image was obtained by using an argon laser in a scann ing laser ophthalmoscope and was recorded on magnetic tapes at a video rate. The images were analyzed by a personal computer-based image ana lysis system. RESULTS. Leukocyte velocities in the retinal capillaries were significantly decreased immediately after photocoagulation. In t he laser-treated area, mean capillary leukocyte velocities were 0.73, 0.92, 1, and 1.3 mm/second on days 4, 7, 14, and 28, respectively (vel ocity in normal control animals 1.4 mm/second). in addition, leukocyte hemodynamics were compromised in the untreated retina: Mean capillary leukocyte velocities were 0.88, 1.1, 1.2, and 1.3 mm/second on days 4 , 7, 14, and 28, respectively. Twenty-eight days after photocoagulatio n, the velocities recovered to normal values in the treated and the un treated areas of the retina. CONCLUSIONS. Retinal capillary hemodynami cs were impaired after scatter photocoagulation, and the hemodynamics in the untreated retina were also affected. Photocoagulation to the re tina may influence capillary hemodynamics by diffusible chemical subst ances and by direct tissue injury.