[In vivo and in vitro study of experimental occlusion of choroidal and retinal blood vessels in the miniature pig].

Experimental occlusion of ocular blood vessels was performed in 25 eyes of 20 adult miniature pigs. The hyperacute, acute, subacute and chronic effects of these occlusions were studied by photography and fluorescein angiography of the ocular fundus in the living animals, and post-mortem by microscopic examination of histologic sections and stereomicroscopic study of vascular corrosion casts. Transection of the lateral posterior ciliary arteries was performed in eleven eyes and resulted in manifest chorioretinal ischaemic atrophy in confined areas of the ocular fundus. One month and longer after arterial transection, revascularization was found in the areas in which hypoperfusion had been induced, but no indications of neovascularization were observed. In one eye the lateral vortex veins were occluded by ligation. The subsequent fluorescein angiograms demonstrated only an insignificant local retardation of the choroidal filling. Filling defects of the choroidal vasculature and chorioretinal ischaemic lesions were not observed in the living animal nor in the vascular corrosion cast. Transection of the lateral posterior ciliary arteries was combined with ligation of the lateral vortex veins in seven eyes. These experiments resulted in lesions which were less severe than the sequels caused by transection of the lateral posterior ciliary arteries only. This observation was explained by the retrograde flow of venous blood which is rich in oxygen from the medial to the lateral choroidal quadrants. Consequently, ligation of the lateral vortex veins has a protective influence on the acute ischaemic lesions provoked by transection of the lateral posterior ciliary arteries. Simultaneous transection of the lateral posterior ciliary arteries and lateral chorioretinal arteries was performed in eight eyes. In the subacute and chronic stages, 1 and 4 months respectively after the vascular transection, proliferation of the retinal pigment epithelium and intraretinal neovascularization were observed in three out of five eyes examined. A fibrogliotic tissue mass containing newly formed blood vessels was found in between the reduplicated retinal pigment epithelium and the external layers of the sensory retina. The miniature pig offers an interesting ophthalmologic model because the ischaemic chorioretinal lesions and intraretinal gliovascular membranes which can be induced experimentally in this species present numerous similarities with the sequels of chorioretinal vascular occlusions in man.