Some sources define "exophthalmos" as a protrusion of the globe greater than 18 mm and "proptosis" as a protusion equal to or less than 18 mm. Others define "exophthalmos" as protusion secondary to endocrine dysfunction and "proptosis" as any non-endocrine-mediated protusion (Source: Wikipedia). This finding should be distinguished frm underdevelopment of the supraorbital ridge or maxilla/zygoma. In proptosis, the globe is anteriorly protuberant to the overall plane of the face.