A large number of people with acceptable uncorrected or best-corrected daytime vision can experience night vision complaints, whether they be people with 'night myopia', people with Intraocular Implants (IOLs), cortical cataracts, or people who have had refractive surgery. Many of these people have corneal or lenticular aberrations, either naturally occurring or surgically introduced. For these people, when the pupil dilates in dim light, some light rays are not focused on the retina, resulting in visual aberrations including glare, ghosting, halos and starburst. It has been proposed that a modest pharmacologic reduction of pupil size has the potential to mitigate these complications in many affected individuals. The purpose of the present study is to evaluate the sub-acute effect of two dose levels of PM on contrast sensitivity and visual acuity during 15 days of continuous therapy.