Normal retinal vascular pattern. Arteriovenous ratio as a measure of arterial calibre.

THis paper is the first of a series on the retinal vessels and is concerned with the normal range of the retinal vascular pattern. It is intended to serve as a foundation for a long-term study of the vascular changes in patients undergoing treatment for hypertension. In particular, its purpose is to expose fallacies in the customary method of assessing arteriolar calibre by the arteriovenous ratio and to discuss diffuse arteriolar narrowing as an early sign of hypertension.