Keratoconus is a ocular disease classified under ectatic diseases which often results in bilateral and asymmetrical corneal distortion. It usually affects patients at young age and can cause severe visual loss. The overall goal of this study is to assess the prevalence of keratoconus (KC) in children and adolescents in various regions of the world based on modern tomographic imaging methods, and to verify whether the occurrence rates reported from literature should be corrected. Our hypothesis is that the prevalence of the disease is much higher than that traditionally reported. At each site, corneal tomography examinations (Pentacam) will be performed bilaterally in children and adolescents, who are not ill or with any ophthalmological symptom. The population to be studied will be composed of children and adolescents on medical visits for non-ophthalmologic reasons, aged between 6 and 20 years. Multiple cities, from different continents (North America, South America, Asia and Europe) will participate.