Design of the empirical study and subjects
COLOR VISION DEFICIENCY, PATHOLOGY, LENS
A prospective, randomized, double-masked, contralateral design was used. Subjects were habitual wearers of spherical silicone hydrogel soft contact lenses with best-corrected visual acuity of 20/25 or better in each eye. Ishihara pseudoisochromatic plates were used to screen for color vision deficiency, and a basic clinical exam was used to exclude any overt ocular pathology (no subjects had to be excluded). A total of 61 subjects were enrolled from one clinical site (Georgia Center for Sight, Greensboro, GA). All enrolled subjects were randomly assigned to one of the two lens sequences (test/control or control/test) and completed the study (the lenses were worn throughout the single test session). All 61 subjects were included in the safety population, which included 31 subjects 18 to 39 years old (50.8%) and 30 subjects 40 to 65 years old (49.2%). Two age groups were selected to assess any change due to age; for example, lens yellowing with age is a possible additive influence (