STUDIES OF THE GENERATION OF EXPERIMENTAL THROMBOSIS BY ILLUMINATION WITH INTENSE LIGHT

The obstruction of glass capillaries perfused with citrated blood by irradiation with intense light has been performed in order to simulate photocoagulation of retinal vessels under greatly simplified conditions. Flow velocities were varied between 0.5 and 5 cm sec-1 and temperature and change of flow velocity were studied for irradiations which were followed by occlusive and non-occlusive events. The experiments indicate that irradiation-induced temperature rise interferes strongly with blood rheology when blood temperatures of about 60°C are approached. For flow velocities below 2.5 cm sec-1, the minimum temperature leading to vessel obstruction was found to be 60°C, whereas for higher flow velocities this minimum thrombus inducing temperature rises rapidly. The rheological events leading to thrombus formation are complex, as evidenced by the flow velocity and temperature changes recorded during irradiation.