I agree with the doctor below. Classically, your nostril width should approximate you inner canthi (inner corners of your eyes). However, this can be wider in certain ethnicities.Aaron Kosins, MDPlastic & Rhinoplasty Surgeon
What you are stating about the nostril width being equal to the distance between the corner of the eyes is classic teaching in rhinoplasty. In a world in which people have very different ethnic facial features and sometimes mixtures of different ethnicities, there really isn't one true "ideal." The concept is more to blend your nose to match well with your other facial features.