 For the following year, he was an NIH special fellow under Bernard Becker in the department of ophthalmology at Washington University in St. Louis.Returning to the University of Iowa College of Medicine in 1972 to join its faculty, Phelps succeeded his mentor Armaly as director of the department of ophthalmology's glaucoma service.He attended to hundreds of patients, educated scores of medical students, and wrote dozens of articles for medical journals reporting on the findings of the medical studies he oversaw.