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There are some evidence of the association between the calibre of the retinal blood vessels and hypertension. Computer-assisted procedures have been proposed to measure the calibre of retinal blood vessels from high-resolution photopraphs. Most of them are in fact semi-automatic. Our objective in this paper is twofold, to develop a totally automated system to classify retinal vessels into arteries and veins and to compare the measurements of the arteriolar-to-venular diameter ratio (AVR) computed from the system with those computed from observers. Our classification method consists of four steps. First, we obtain the vascular tree structure using a segmentation algorithm. Then, we extract the profiles. After that, we select the best feature vectors to distinguish between veins and arteries. Finally, we use a clustering algorithm to classify each detected vessel as an artery or a vein. Our results show that compared with an observer-based method, our method achieves high sensitivity and specificity in the automated detection of retinal arteries and veins. In addition the system is robust enough independently of the radii finally chosen, which makes it more trustworthy in its clinical application. We conclude that the system represents an automatic method of detecting arteries and veins to measure the calibre of retinal microcirculation across digital pictures of the eye fundus.

Fundamento y objetivo Las guias europeas de hipertension arterial consideran que es necesario un metodo que cuantifique de forma objetiva los cambios iniciales en la microcirculacion retiniana del hipertenso. Previamente hemos descrito y validado un metodo semiautomatico basado en un modelo lineal, con una alta sensibilidad y especificidad, pero con limitaciones. Fundamento y objetivo Por este motivo, desarrollamos un metodo basado en el modelo de snakes, para medir el indice arteriovenoso retininano y lo hemos comparado con el metodo previamente descrito. Pacientes y metodo Para validar este metodo, hemos analizado las fotografias digitales obtenidas de 173 ojos pertenecientes a un total de 96 pacientes hipertensos; la mayoria de estos estaban recibiendo tratamiento. Las fotos se han realizado en 2 centros: A Coruna (66) y Santiago de Compostela (107), y la misma persona los ha analizado mediante ambos metodos en cada centro (lineal y snake). Resultados Hemos observado que las medias y las diferencias de las determinaciones del indice arteriovenoso por ambos metodos son minimas y siguen una distribucion normal. El estadistico alfa de Cronbach fue de 0,974, con un coeficiente de correlacion intraclase de 0,949 (p