Abstract
Abstract: :
Purpose:To determine the location of pressure induced areas of non–fluorescence of choroidal vessels detected by indocyanine green (ICG) angiography. Methods:In order to visualize the choroidal circulation more clearly by ICG angiography, vitrectomy and local retinectomy were performed prior to producing local pressure indentation of the retinal pigment epithelium (RPE) and choroid. The pressure applied was less than 0.1 to 1 mm Hg. The choroidal vessels were monitored by ICG angiography at minutes, hours and days after the procedure. The retina and choroid were studied histologically. Results:Transient pressure indentation of the RPE layer and choroid produced local staining both of arteries and veins and delayed filling and/or blockage of segments of the large choroidal vessels, especially veins. The changes were reversible within about 1–2 days. Conclusions:The large choroidal vessels of the rabbit are very sensitive to pressure. Slight pressure indentation produces local areas of delayed filling and/or non–perfusion and staining of these vessels, which takes days to recover. The mechanism for these changes is considered to be a vessel response, perhaps the endothelium, to pressure leading to ICG staining and vessel blockage. We hypothesize that the change is due to either the formation of small thrombi or a neural reflex causing constriction.
Keywords: choroid • retinal pigment epithelium • ischemia