Vertex Conversion Chart app can be used by optometrist, Eye doctor and also people wearing contact lens. This app is used to convert the lens power in Spectacle prescription to lens power needed for contact lens. Inputs required for the conversion are Vertex distance and Spectacle prescription power.

Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea.

Spectacle prescription power is the lens power required to correct the refractive error of the eye.