Patho-physiological Investigation on the Retinal Circulation and Diagnosis of the Retinal Vessel Function in Essential Hypertension and Cerebral Arteriosclerosis

Abstract

Eye ground findings recorded by the criteria of Keith-Wagener or Scheie in essential hypertension and cerebral arteriosclerosis, have proven to be of much value clinically. However, these observation are mostly morphological and do not express were hemodynamic changes. Studies in our department have been centered around the vessel reaction of verious organs caused by induced hypoxemia and the findings concerning the coronary, cerebral, hepatic, and renal circulations have been reported previously. Recently, the determination of retinal blood flow has been established by ophthalmologists and this prompts us to study the hemodynamics of the retinal circulation during the resting state and during induced hypoxemia with the purpose of investigating the pathophysiology of the retinal circulation and the possibility of advancing a step towards the diagnosis of retinal vessel function. Methods and Materials A) Methods used : Values concerning retinal hemodynamics during the resting state were calculated by measuring the brachial and retinal blood pressures and eye ground photography. Immediately after those Procedures a mixture of 10% O₂ and 90% N₂ was administered for 20 minutes and the above procedures were repeated to determine the retinal hemodynamics during the induced hypoxemia. B) Calculations i) Retinal blood flow was calculation by the Hagen-Poiseuille law. ii) Comparison of central retinal artery and brachial artery blood pressures. iii) Systolic blood pressure ratio iv) Diastolic blood pressure ratio v) Pulse pressure ratio vi) Further relative differential pressure ratio