Systems for determining an individuals current focal plane by measuring parameters associated with binocular vision focusing using one or two contact lenses are provided. In an aspect, a system includes a first contact lens and a second contact lens respectively configured to be worn over first and second eyes of an individual. The first contact lens and the second contact lens respectively include first and second substrates, and first and second circuits respectively disposed on or within the first and second substrates and configured to respectively generate first data related to a focal trajectory of the first eye and second data related to a focal trajectory of the second eye, wherein the first circuit employs the second contact lens to generate the first data and the second circuit employs the first contact lens to generate the second data.
