Trans-ocular hypertension assessment

Abstract

Abstract Blood vessel walls are made of organized fibrous tissue with intrinsic birefringence. Even in its very early stages, hypertension can change the structure of a blood vessel wall. We showed that this structural change can be quantitatively measured non-invasively in the human retina using polarization-sensitive optical coherence tomography (PS-OCT). Organizational loss in vessel wall tissue was quantified in hypertensive patients and compared to data obtained from age-matched healthy subjects. The wall tissue in patients with hypertension was shown to be thicker, and exhibited lower birefringence, presumably due to a loss of tissue organization. The blood vessel wall birefringence index (BBI) combines vessel wall birefringence and thickness into one number and is introduced here to readily distinguish between blood vessel walls of hypertensive and healthy subjects. Based on receiver operating characteristic (ROC) curves, BBI showed 99% sensitivity and 100% specificity when discriminating normotensive (N = 11) and hypertensive (N = 11) subjects. Accurately determining the thickness of the blood vessel wall is not possible without polarization-sensitivity. Moreover, just blood vessel wall thickness or wall birefringence were not sufficient to achieve this high classification performance. Retinal vessel wall measurements with PS-OCT cannot be affected by a patient being anxious, by hormones or other blood values, since the measurement is intrinsic to the optical and mechanical properties of the vessel wall. Furthermore, this relatively low-cost system combines a very short imaging and analysis time with high sensitivity and specificity, making it highly suitable for low-cost screening.