Stern sought addition as a co-inventor on Bito's patent for treating glaucoma. The C.A.F.C. found that co-inventors must both contribute to the conception of an invention. Conception is complete when "the idea is so clearly defined in the inventor's mind that only ordinary skill would be necessary to reduce the invention to practice." Stern was a medical student at Columbia University, where he performed one semester of ophthalmology research in Bito's laboratory. He performed tests under the Bito's direction, after reviewing Bito's publications. Stern only tested single applications of prostaglandins, where the patented treatment uses repetitive applications. Further, no evidence of collaboration was presented. Accordingly, the C.A.F.C. upheld the lower courts that Stern failed to present clear and convincing evidence of co-inventorship.