Contact lenses are ocular prosthetic devices used by over 150 million people worldwide. Primary applications of contact lenses include vision correction, therapeutics, and cosmetics. Contact lens materials have significantly evolved over time to minimize adverse effects associated with contact lens wearing, to maintain a regular corneal metabolism, and to preserve tear film stability. This article encompasses contact lens technology, including materials, chemical and physical properties, manufacturing processes, microbial contamination, and ocular complications. The function and the composition of the tear fluid are discussed to assess its potential as a diagnostic media. The regulatory standards of contact lens devices with regard to biocompatibility and contact lens market are presented. Future prospects in contact lens technology are evaluated, with particular interest given to theranostic applications for in situ continuous monitoring the ocular physiology.

Tears exhibit compositional variations as a response to ocular and systemic metabolic conditions, and they can therefore be used for the assessment of physiological health. Here, microfluidic contact lenses were developed as wearable platforms for in situ tear pH, glucose, protein, and nitrite ions sensing. The microfluidic system was inscribed in commercial contact lenses by CO2 laser ablation. The microchannel consisted on a central ring with four branches, and biosensors were embedded within microcavities located at the branches ends. The device was tested with artificial tears and colorimetric readouts were performed using a smartphone-MATLAB algorithm based on the nearest neighbor model. Sensors responded within a time range of 15 seconds, and yielded sensitivities of 12.23 nm/pH unit, 1.4 nm/mmolL -1 of glucose, 0.49 nm/gL -1 of proteins, and 0.03nm/μmolL -1 of nitrites. Contact lens sensing platforms may provide on-eye tears screening with applications in the monitoring of the ocular health both in clinics and at point-of-care settings.

In this paper, using the integration of paper microfluidics within laser-inscribed commercial contact lenses, we demonstrate the multiplexed detection of clinically relevant analytes including proteins, glucose, nitrites and L-ascorbic acid,...