Histological Study in Choroidal Vascular Occlusion Induced by Laser Irradiation Combined with Fluorescein Injection

ABSTRACT

The purpose of this study is to observe the choroidal vascular occlusion by photocoagulation under intravenous administration of fluorescein sodium. Argon laser photocoagulation(intensity 50 mW, duration 0.05 sec., spot size 200 micrometer) was applied to the retina of the left eye(control group) and the same method was repeated to the right eye combined with intravenous infusion of 2 ml of fluorescein sodium in the pigmented rabbit(experimental group). The photocoagulated rabbit eyes were enucleated after 2 hrs, 1, 3 and 5 days and the retina and choroid were observed under electron microscopy. The result were as follows. 1. In the control group, loss of melanin pigments in the retinal pigment epithelium and destruction of outer segments of the photoreceptor were observed but endothelial cells of choriocapillaris and Bruch's membrane were intact. 2. In the experimental group, two hours after irradiation, endothelial cells of choriocapillaries were destroyed and capillary lumen was occupied with thrombus components, the retinal pigment epithelium and outer segment of the photoreceptor cells were also destroyed. One day after irradiation, occupied materials in lumen were absorbed but residual debris of thrombus was demonstrated. Three days after irradiation, newly formed endothelial cel1 processes were extended in the area of destroyed choriocapilJaries. Five days after irradiation, long processes of newly fonned endothelial cells extended in the area of choriocapillaries. The outer part of retina was repaired with newly formed pale pigment epithelium and proliferated Miil1er cells. 3. In conclusion, argon laser-provoked vascular change was more easily recognized by intraluminal fluorescein sodium which probably acted as an energy absorbent.