The fourth year of the professional program at the College of Optometry consists of six eight-week advanced clinical rotations (externships) in the core optometric discipline. One of the rotations must have an ocular disease emphasis and one must be in a large general clinical setting. A minimum of two fourth-year rotations must be taken under the supervision of St. Louis-based College of Optometry faculty. Externships are permitted in private optometric or ophthalmological practices.