A method for highly accurate determination of a pupil diameter of an eye, by means of a camera system for spatial detection of objects, the method comprising: - Imaging stereoscopically a region of an eye of a head, using the camera system, resulting in first and second stereoscopic images (110, 111) for an eye of the region of the eye; and for each of the two stereoscopic images (110, 111), the method further comprises: - transferring the captured eye region of the head into a color space, and continuing the method in said color space, - determining an area within the sensed eye region, as an area within a pupil of the eye of the sensed eye region, the determined area within the sensed eye region having an image criterion, wherein the image criterion represents a substantially homogeneous image criterion, wherein for a substantially homogeneous image criterion an image property has homogeneity at least in a significantly large area of the image, - determining a closed outer edge of the area within the pupil, - iteratively determining a closed outer pupil margin, comprising iteratively determining the outer pupil margin: - circumferentially determining the outer rim a further area outside the rim, along the rim, the further area being adjacent to the closed outer rim of the area inside the pupil, - iteratively examining the further region to determine whether the further region exhibits the image criterion, and if at least a part of the further area has the image criterion: - Integrating that part of the further area which has the image criterion into the area inside the pupil of the eye, - extending the closed outer edge of the area within the pupil to the integrated part of the further area, and if the further area completely lacks the image criterion: - determining the closed outer edge of the area within the pupil as the outer edge of the pupil of the eye, and - determining a third area as the pupil of the eye, wherein the third area is the area completely enclosed by the outer edge of the pupil. - Imaging stereoscopically a region of an eye of a head, using the camera system, resulting in first and second stereoscopic images (110, 111) for an eye of the region of the eye; and for each of the two stereoscopic images (110, 111), the method further comprises: - transferring the captured eye region of the head into a color space, and continuing the method in said color space, - determining an area within the sensed eye region, as an area within a pupil of the eye of the sensed eye region, the determined area within the sensed eye region having an image criterion, wherein the image criterion represents a substantially homogeneous image criterion, wherein for a substantially homogeneous image criterion an image property has homogeneity at least in a significantly large area of the image, - determining a closed outer edge of the area within the pupil, - iteratively determining a closed outer pupil margin, comprising iteratively determining the outer pupil margin: - circumferentially determining the outer rim a further area outside the rim, along the rim, the further area being adjacent to the closed outer rim of the area inside the pupil, - iteratively examining the further region to determine whether the further region exhibits the image criterion, and - transferring the captured eye region of the head into a color space, and continuing the method in said color space, - determining an area within the sensed eye region, as an area within a pupil of the eye of the sensed eye region, the determined area within the sensed eye region having an image criterion, wherein the image criterion represents a substantially homogeneous image criterion, wherein for a substantially homogeneous image criterion an image property has homogeneity at least in a significantly large area of the image, - determining a closed outer edge of the area within the pupil, - iteratively determining a closed outer pupil margin, comprising iteratively determining the outer pupil margin: - circumferentially determining the outer rim a further area outside the rim, along the rim, the further area being adjacent to the closed outer rim of the area inside the pupil, - iteratively examining the further region to determine whether the further region exhibits the image criterion, and if at least a part of the further area has the image criterion: - Integrating that part of the further area which has the image criterion into the area inside the pupil of the eye, - extending the closed outer edge of the area within the pupil to the integrated part of the further area, and - Integrating that part of the further area which has the image criterion into the area inside the pupil of the eye, - extending the closed outer edge of the area within the pupil to the integrated part of the further area, and if the further area completely lacks the image criterion: - determining the closed outer edge of the area within the pupil as the outer edge of the pupil of the eye, and - determining a third area as the pupil of the eye, wherein the third area is the area completely enclosed by the outer edge of the pupil. - determining the closed outer edge of the area within the pupil as the outer edge of the pupil of the eye, and - determining a third area as the pupil of the eye, wherein the third area is the area completely enclosed by the outer edge of the pupil.