 Once consent is obtained the subject will choose from available time slots. Each subject will come to the UIHC Department of Ophthalmology at designated times for approximately one hour on five different days, for a total time commitment of approximately 5 hours. Each subject will receive the same 4 artificial tear substitutes and saline, one different drop each day. One of the four tear substitutes brands: Systane, Systane Ultra, Optive, and Refresh will be tested on each of the days. One drop will be used each day and the protocol of each day will be the same, the only factor changing from day to day is the drop that is being evaluated. On each study day, the subject will have a pre-instillation measurement of their higher order aberrometry of each eye. One drop of the designated drop will be placed into each of the eyes. Subsequent aberrometry measurements of each eye will be taken at immediately post-instillation, 5 minutes, 30 minutes and 60 minutes post instillation. The same protocol will be followed with a saline drop and thus each patient will act as a control. 