title: [Estimation of the retinal microvascular calibre in hypertensive patients with the snakes semiautomatic model].
abstract: OBJECTIVE
  Early alterations in retinal microcirculation are observed in most hypertensive patients seen in daily practice and the European guidelines consider it is necessary an objective method to quantify these alterations. We have previously described a semi-automatic computerized system to evaluate the calibre of retinal blood vessels that has shown high sensitivity and specificity to calculate the arteriovenous ratio (AVR), though with limitations. We describe a method based on the snakes model to calculate the arteriovenous ratio.
  
  
  METHODS
  We had compared it with the previously reported lineal method, and we have analyzed 173 digital photographs from 96 hypertensive patients, most of them receiving treatment. Photos were made in two hospitals (A Coruña: 66 and Santiago de Compostela: 107), and were analysed by the same people in each Centre, by the lineal and snake method.
  
  
  RESULTS
  We have observed that the arithmetic mean and the differences in AVR between both methods were minimal and showed a normal distribution. Cronbach statistics was 0.974 and intraclass correlation coefficient 0.949 (p<0.001), for the images from Santiago and 0.923 with an intraclass correlation coefficient of 0.857 (p<0.001) for the images from A Coruña.
  
  
  CONCLUSIONS
  This semiautomatic method to calculate the AVR ratio has a high sensitivity and a greater specificity than previous method, and the correlation between the results obtained with both is excellent.
authors.affiliation: Unidad de Pluripatología, Servicio de Medicina Interna, Departamento de Medicina, Hospital de Conxo, Complexo Hospitalario Universitario de Santiago de Compostela, Santiago de Compostela, Spain. antoniopose@telefonica.net
authors.forename: Antonio
authors.initials: A
authors.lastname: Pose-Reino
authors.forename: Marta
authors.initials: M
authors.lastname: Pena Seijo
authors.forename: Manuel
authors.initials: M
authors.lastname: González Penedo
authors.forename: Marcos
authors.initials: M
authors.lastname: Ortega Hortas
authors.forename: María
authors.initials: M
authors.lastname: Rodríguez Blanco
authors.forename: Pilar
authors.initials: P
authors.lastname: Vega
authors.forename: José Luis
authors.initials: JL
authors.lastname: Díaz Díaz
authors.forename: Noa
authors.initials: N
authors.lastname: Fernández
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Estévez
authors.forename: Francisco
authors.initials: F
authors.lastname: Gómez-Ulla Irazábal
mesh_terms: D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D006973:Hypertension / Q000473:pathology*; D008833:Microcirculation; D015233:Models, Statistical; D012171:Retinal Vessels / Q000473:pathology*