Abstract: A method for determining one or more dimensions of an object in a two-dimensional image, wherein the image includes the iris of a human being. A size ratio is estimated between the dimension of the object and the diameter of the visible iris, by analyzing the two-dimensional picture. Then, the dimension of the object is approximated based upon the size ratio and also based upon the invariant iris diameter. Use is made of the fact that the diameter of a human iris is substantially identical for all humans above the age of two, and thus an image which includes someone's iris furnishes a measuring device for determining other dimensions in the image. The present invention is especially suited for examining, virtually trying on, and purchasing eyewear from a remote location.