The apparent and true width of the blood column in retinal vessels

Abstract Changes in the caliber of retinal vessels may be of haemodynamic and morphological significance in various local and systemic vascular diseases. In this paper we present a theoretical study on the effects of structural density changes of the vessel wall on the ‘true’ width of the streaming column of erythrocytes. By use of simplified models of an eye and a retinal vessel, we perform numerical experiments using a computer. The results show that variations in the index of refraction and in the thickness of the vessel wall have negligible influence on the apparent width of the blood column. The image of the vessel can safely be measured as a ‘true’ caliber of the retinal blood column. This might implicate that an early differentiation between vessel constriction caused by increased tonus of systemic‐hypertension versus irreversible arteriosclerosis is probably not within physical and optical reach, using ophthalmoscopy.