RecruitingPhase 4Drug trialThe Effects of 3% Trehalose Ophthalmic Solution on Corneal Epithelial Barrier FunctionThe purpose of this research study is to evaluate the effects of trehalose, an ingredient found in commercially available artificial tears, on the corneal barrier function. The investigators will assess corneal dryness and measure the relative corneal epithelial "barrier" function (the degree to which the cornea can prevent penetration of sodium fluorescein dye into the eye) after using eye drops that contain 3% trehalose for one month.