Tears Substitutions and Their Effects on Higher Order Aberrometery

Hypothesis is that tear substitutions cause blur after they are instilled. The investigators will use aberrometry as a measurement over time after a tear formulation is used and try to determine if there are any measurable change in higher order aberrations between different tear formulations and how long it takes to return to pre-instillation measurements thus providing information on duration of the tear drop. 4 commercially available "dry eye" artificial tears formulations will be used and preservative saline will act as a control. The study will be conducted on subjects that do not have clinical evidence of dry eye syndrome to focus the data on the blur effects of the tear substitutions.