Inclusion Criteria:  Males or females aged 18-39 years who currently wear glasses and/or soft contact lenses to correct refractive error Normal color vision Able to use both hands at the same time and to hear, understand and verbally respond to audio instructions Have single vision lenses only Able to provide informed consent -  Exclusion Criteria:  Have any ongoing disease or ocular condition other than refractive error Have a history of permanent vison loss Have a neurological condition affecting vision Have worn glasses since age 6 or younger Have a prism in their prescription Use Rigid gas permeable lenses or OrthoK lenses Have had laser refractive surgery or any other eye surgery Use prescription eye drops -