Apparatus, systems and methods are provided that employ contact lenses that facilitate testing for an analyte present within tear fluid. In an aspect, a contact lens includes a substrate that forms at least part of a body of the contact lens and one or more cavities disposed within the substrate configured to collect and store tear fluid over time when the contact lens is worn over an eye. In another aspect, a contact lens includes a substrate that forms at least part of a body of the contact lens and one or more receptors disposed on or within the substrate, the one or more receptors are configured to bind to a known ligand.
