Contrast letter acuity as a visual component for the Multiple Sclerosis Functional Composite. - Balcer LJ; Baier ML; Cohen JA; Kooijmans MF; Sandrock AW; Nano-Schiavi ML; Pfohl DC; Mills M; Bowen J; Ford C; Heidenreich FR; Jacobs DA; et al. (Neurology, 2003)