1. A method of determining the spatial relationship of an eye of a person with respect to a camera device which provides images of the eye, the method comprising: in a model acquisition phase: constructing a three-dimensional shaped customized model of the eye representing the surface of the eye and having texture information associated with a plurality of points located on the surface of the eye, the texture information stored as a feature template map including three-dimensional model coordinates of a plurality of reference image points at which eye features are located, and the feature template map having templates containing parts of the reference image extracted around each associated point and showing the corresponding eye feature, determining a reference spatial relationship of the eye model with respect to the camera device using a reference image of the eye, and aligning the eye shaped model to the reference image of the eye; and in a tracking phase: determining position and/or rotation coordinates of the eye by aligning the eye model to a current image of the eye, and performing: a) a template matching step in which, for a plurality of feature templates stored in the feature template map, a region in the current eye image bearing the largest resemblance to the respective feature template is searched; b) a coordinate determination step in which the coordinates of the regions found in step a) are determined as respective current feature positions; and c) an alignment step in which an image distance between the current feature positions determined in step b) and the positions of the corresponding three-dimensional model features projected into the current eye image is minimized by fitting position and/or rotation parameters of the eye model.