Towards retinal vessel parameterisation

The reliable measurement of retinal vessel geometry in ordinary red-free fundus photographs is a challenging issue. Quite apart from refractive effects which can distort absolute measures, the existence of the central light reflex poses some interesting problems in vessel modelling and segmentation. One aim of our research is to obtain subpixel vessel width precision from digitised retinal photographs. For this purpose, we require a reasonable physical and mathematical model for the vessel intensity profile. In this paper, we review physical principles behind the image formation, leading to a twin Gaussian model. We test 4 non-linear parametric models based on Gaussian forms. Some applications of this model-based approach are introduced, including the parametric determination of vessel centre and the accurate determination of vessel width in typical noisy clinical images.