Smart Contact Lens – A Future Technology

Krishna Shah, M. Optom

Student, The Sankara Nethralaya Academy (TSNA), Chennai, India

 

Introduction

Smart contact lens is a device built on a biocompatible polymer contains ultrathin, flexible electrical circuits and a microcontroller chip for real-time electrochemical biosensing, on-demand controlled drug delivery, wireless power management, and data communication.⁽¹⁾

Figure 1: A contact lens biosensor Conceptual illustration
Picture courtesy: Tseng -Contact lens biosensors. Sensors

Table 1: Comparison of various smart contact lenses ⁽¹⁾

Smart contact lens types	Biosensing	Glucose sensing range	Therapy	Power system	Data transfer	Current status
Triggerfish	Intraocular pressure	×	×	Inductive coupling	RF communication	FDA-approved
Google lens	Glucose	0 ~ 36 mg dl−1	×	Inductive coupling and Li battery	Reflectance from inductive coupling	Clinical
The Park group contact lens	Intraocular pressure and glucose	0 ~ 180 mg dl−1 (log scale dependence)	×	Inductive coupling	Reflectance from inductive coupling	In vivo
The Parviz group contact lens	Glucose	0 ~ 36 mg dl−1	×	Online power, RF power	Line connection, backscatter communication	In vitro
Our smart contact lens	Glucose	0 ~ 50 mg dl−1	Drug delivery	Inductive coupling	RF communication	In vivo

1. Diagnosis and screening for systemic disease

Tear film contains a wide range of biomarkers that may help diagnose systemic disease for a range of conditions.⁽²⁾

Table 2: Systemic disease biomarkers found within the tear film.⁽³⁾

Disease	Potential tear biomarkers
Alzheimer’s disease	Increased levels of dermcidin, lacritin, lipocalin-1 and lysozyme C
Cancer	Increased levels of lacryglobin, changes in combination of specific proteins
Cystic fibrosis	IL-8 and IFN-γ [6], MIP-1α and MIP-1β
Diabetes	Increased levels of glucose, advanced glycation end products, cytokine changes
Multiple sclerosis	Oligoclonal bands of IgG and α-1-antichymotrypsin
Parkinson’s disease	TNF-α and oligomeric alpha-synuclein
Thyroid disease	IL-1β, IL-6, IL-17, TNF-α [17] and IL-7 [18]

*IL – Interleukin; IFN – Interferon; MIP – Macrophage inflammatory protein; TNF – tumour necrosis factor; IgG – Immunoglobulin G.

Figure 2: Overview of tear-based wearable medical devices
Picture courtesy: Tseng Contact-lens biosensors. Sensors, 18(8), 2651.

1.1. Diabetes monitoring via tear-film glucose detection

Non-invasive methods for glucose detection to alleviate discomfort and inconvenient caused by invasive methods also reducing the risk of loss of sensation and secondary infection.4Diabetes patients have greater tear glucose concentrations than healthy people and several groups have proposed contact lens-based biosensors to measure tear glucose levels. ⁽⁵⁾

1.2 Cancers

In recent years, mounting data has suggested that tear fluid contains cancer indicators. Lacryglobin was discovered in the tear fluid of those suffering from colon, prostate, breast, lung, and ovarian cancers, according to the group’s ground-breaking study. This study proved that biomarkers found in tear fluid can help in non-invasive cancer detection using contact lenses. contact lens can play an important role in detection of cancer patients.⁽⁶⁾

2. Diagnosis and screening for ocular disease

2.1 Contact lens-based devices to monitor IOP

Triggerfish contact lens sensor is a commercially available smart contact lens device that enables prolonged IOP monitoring.⁽⁷⁾ It has received FDA approval for 24 hours measurement of IOP. The device also analyses tiny dimensional changes in corneal shape, which are related to changes in both IOP and the volume and biomechanical characteristics of the eye. Measurements are recorded for 30 sec periods every 5 min during wear, providing 288 datapoints over a 24 -hours period.⁽⁸⁾

Figure 3a: Contact lens sensor

Figure   3b:   Sensor transmitting information gathered through antenna, which is connected to a portable recorder.

Researchers have developed a prototype contact lens that measures the ocular surface temperature, tear evaporation rate, and tear osmolarity.

In DED, a range of chemokines/cytokines level are increased in the tears, including TNF-α, IL-6, IL-17a and IL-8. This type of technology would allow continuous monitoring of the system, which could be helpful tools in the detection and monitoring of DED and other ocular surface diseases. ⁽⁹⁾

2.3 Diabetic Retinopathy

To minimise hypoxia during sleep, researchers have considered various methods of delivering light to the retina during eye closure and the development of a phosphorescent contact lens for treatment of diabetic retinopathy. This design allows unobstructed vision under photopic conditions, whilst under scotopic conditions the enlarged pupil allows the retina to receive the phototherapeutic dose.⁽¹⁰⁾

Conclusion

Today, Biosensors are widely used in many facets of healthcare. The rapid growth in novel biomaterials and the development of smart contact lenses through advancements in nanotechnology will enable the commercialisation of lenses that can detect and treat systemic and ocular disease.

 

References

1. Keum, D. H., Kim, S. K., Koo, J., Lee, G. H., Jeon, C., Mok, J. W., … & Hahn, S. K. (2020). Wireless smart contact lens for diabetic diagnosis and therapy. Science advances, 6(17), eaba3252.

2. Heinemann, L. (2008). Finger pricking and pain: a never-ending story. Journal of diabetes science and technology, 2(5), 919-921.

3. Jones, L., Hui, A., Phan, C. M., Read, M. L., Azar, D., Buch, J., … & Willcox, M. (2021). BCLA CLEAR–Contact lens technologies of the future. Contact Lens and Anterior Eye, 44(2), 398-430.

4.Aihara, M., Kubota, N., & Kadowaki, T. (2018). Study of the correlation between tear glucose concentrations and blood glucose concentrations. Diabetes,67(supplement_1)

5. Evans, V., Vockler, C., Friedlander, M., Walsh, B., & Willcox, M. D. (2001). Lacryglobin in human tears, a potential marker for cancer. Clinical & experimental ophthalmology, 29(3), 161-163.

6.Chen, G. Z., Chan, I. S., Leung, L. K., & Lam, D. C. (2014). Soft wearable contact lens sensor for continuous intraocular pressure monitoring. Medical engineering & physics, 36(9), 1134-1139.

7.Leonardi, M., Leuenberger, P., Bertrand, D., Bertsch, A., & Renaud, P. (2004). First steps toward non-invasive intraocular pressure monitoring with a sensing contact lens. Investigative ophthalmology & visual science, 45(9), 3113-3117.

8.Mansouri, K., Medeiros, F. A., Tafreshi, A., & Weinreb, R. N. (2012). Continuous 24-hour monitoring of intraocular pressure patterns with a contact lens sensor: safety, tolerability, and reproducibility in patients with glaucoma. Archives of ophthalmology, 130(12), 1534-1539.

9.Yetisen, A. K., Jiang, N., Castaneda Gonzalez, C. M., Erenoglu, Z. I., Dong, J., Dong, X., & Koch, A. W. (2020). Scleral lens sensor for ocular electrolyte analysis. Advanced materials, 32(6), 1906762.

10. Pugh, R. B. (2018). U.S. Patent No. 9,901,322. Washington, DC: U.S. Patent and Trademark Office.