The search for cephalometric relationship in pictures that have been recognized as beauty symbols in every epoch permits identifying constant values that may be found both in Renaissance paintings as well as in today's beauties. 

Beauty contains the idea of proportion, a word that derives from the Latin pro portio (the correct ratio between the parts) that provides it with a universally comprehensible meaning. Especially during the Renaissance, a true geometry of beauty was attained, following the "rule of three" inspired by Euclid. The cephalometric planes were identified by Leonardo da Vinci who translated the ratios between the physiognomic regions into intersecting lines and showed the simple rule of the multiples that reveals the shape of the profile: three spaces, equal to the height of the ear or nose are the same as the distance between the menton and the trichion. The constant ratio in regular profiles between the nasion, the subnasale and the pogonion, these being cephalometric points susceptible to change after surgery, suggested including the profile in a triangle divided in two equal parts. To make surgical planning simpler and more rapid, we created a fan ruler that instantaneously carries out the cephalometry of the profile, which can be subject to modification depending on the surgeon's aesthetic taste an experience. In fact, the variety of the face morphology and, therefore, corrective surgical techniques thet are selected case by case cannot be limited to an oversimplified geometric interpretation. Moreover, cephalometric rules must be interpreted in light of various factors: the plastic property of the tissues, their ability to change in time and the age and sex of the patient. In the young female patient it may be appropriate to overcorrect the nasal dorsum, in view of the tendency of the nose to change shape in the course of the time, while a decrease in volume is preferable in the adult, with respect to the physiognomic identity. Therefore, surgical planning is neither a simple measure of the facial size nor a mere question of aesthetic taste, but rather a general evaluation of the relationship between the soft tissue, the skin quality, the age and sex of the patient and, lastly, the patient's expectations. The current tendency to perform corrective rhinoplasty with the help of computerized images or cephalometric evaluations is justified by the need to adapt the amount of correction to all the cephalometric ratios and draw on indications regarding the exact quantity of tissue to remove or add, however "precision rhinoplasty" is not a synonym for an absolute foreseeable result, except in cases thet require a very small amount of tissue removal (up to 3 mm, considered as the average between the maximun width of the portion removed from the dorsum and caudal septum). Beyond these limits, the operation itself involves structural alterations thet may escape even the most careful operation analysis.