Precise instantaneous digital measurement of intraocular pressure done non-invasively is a clinical window to the vascular physiology of the eye. This technique has been used to study the pulse amplitude/intraocular pressure curve in 2 distinct clinical entities. The first is amaurosis fugax before and after carotid endarterectomy. This demonstrates the effects of high vascular resistance external to the eye on the ocular blood flow. The second is a patient with long-standing arteriosclerotic cardiovascular disease. This is an illustration of increased vascular resistance within the eye.