Theranostics is an exciting and expanding field of medicine in which the diagnosis of a condition is concurrently coupled with the provision of a therapeutic agent for its treatment (Svenson, 2013). This groundbreaking, multidisciplinary avenue combines elements from a wide range of fields to enable a personalized approach to medicine.

A theranostic system is ambitious, as it requires both a sensing system and a drug delivery system to seamlessly work together, and thus presents a substantial engineering challenge. The incorporation of nanotechnology can be used to achieve success in these systems (for example, using nanoparticles), though care must be taken to meet many requirements, including but not limited to biocompatibility, selective targeting, and successful, therapeutically relevant drug delivery (Chen et al, 2014). The current difficulty of bringing these devices into clinical practice lies in fulfilling all these design elements.

Theranostic applications are currently mostly seen in nuclear medicine, particularly oncology. Specially designed agents labeled with γ-emitting radionucleotides can be used to identify certain markers, such as receptors on tumor cell membranes, allowing identification through imaging techniques such as PET scans (Peltek et al, 2019).

These agents are also combined with an α- or β-emitting radionucleotide that can emit ionizing radiation suitable for therapy directly at the tumor site (Gomes Marin et al, 2020). In relation to the ocular surface, oncology-based theranostic approaches have been identified as having the potential to combat uveal melanoma, the most common form of intraocular cancer (Bilmin et al, 2021).

Contact Lens-Mediated Ocular Surface Treatment

The use of a contact lens platform has been investigated in the development of an ocular theranostic device. Contact lenses conveniently sit on the ocular surface, allowing them to be in continuous contact with—and potentially detect changes in—the tear film.

Several contact lens-based diagnostic devices that have been developed, and some have been commercialized (Dunbar et al, 2017).

In addition, contact lenses have been developed for drug delivery due to their sustained and enhanced drug release profiles, with significant progress being achieved in this regard (Yang and Lockwood, 2022; Rykowska et al, 2021; Maulvi et al, 2021).

The combination of these two applications of contact lenses in a theranostic device seems like the next logical evolutionary step.

Due to the relative infancy of the theranostics field, published work on the use of theranostic contact lenses is minimal. However, based on other areas of medicine that have seen success, dry eye, glaucoma, and diabetes have all been identified as conditions in which theranostics could excel.

Recently, a smart contact lens device was developed that incorporated ultrathin circuitry combined with a microcontroller chip that allowed for real-time monitoring of tear glucose levels. Depending on the level, drug release for the treatment of diabetic retinopathy was triggered from reservoirs in a contact lens polymer (Keum et al, 2020).

This study, and the proposed conditions and theranostic avenues described in Table 1, highlight the exciting promise of how theranostics could be applied to the treatment of ocular diseases through a contact lens platform.

Future Directions

As the development of devices for biosensing and drug delivery further advance, the area of contact lens theranostics becomes increasingly more attractive and viable. Though limitations do need to be addressed, such as a difficulty of embedding feedback sensors in the contact lens to connect diagnosis with the dispensing of the therapeutic agent, this area of medical research has wide-reaching possibilities.

As we look forward to the potential of smart contact lenses capable of theranostics, the eyes could serve as not only the window to the soul but also a doorway to the future approaches of medicine. CLS

References

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