Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Jan 22;12(2):108.
doi: 10.3390/mi12020108.

Wearable Contact Lens Sensor for Non-invasive Continuous Monitoring of Intraocular Pressure

Zhiqiang Dou  1   2 , Jun Tang  1   2 , Zhiduo Liu  1   2 , Qigong Sun  1   2 , Yang Wang  1 , Yamin Li  1   2 , Miao Yuan  1   2 , Huijuan Wu  3 , Yijun Wang  1   2 , Weihua Pei  1   2 , Hongda Chen  1   2
Affiliations

Wearable Contact Lens Sensor for Non-invasive Continuous Monitoring of Intraocular Pressure

Zhiqiang Dou et al. Micromachines (Basel). .

Abstract

Intraocular pressure (IOP) is an essential indicator of the diagnosis and treatment of glaucoma. IOP has an apparent physiological rhythm, and it often reaches its peak value at night. To avoid missing the peak value at night and sample the entire rhythm cycle, the continuous monitoring of IOP is urgently needed. A wearable contact lens IOP sensor based on a platinum (Pt) strain gauge is fabricated by the micro-electro-mechanical (MEMS) process. The structure and parameters of the strain gauge are optimized to improve the sensitivity and temperature stability. Tests on an eyeball model indicate that the IOP sensor has a high sensitivity of 289.5 μV/mmHg and excellent dynamic cycling performance at different speeds of IOP variation. The temperature drift coefficient of the sensor is 33.4 μV/°C. The non-invasive IOP sensor proposed in this report exhibits high sensitivity and satisfactory stability, promising a potential in continuous IOP monitoring.

Keywords: IOP; MEMS; glaucoma; high sensitivity; strain gauge; wearable.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Finite element simulation analysis of corneal deformation profile under the IOP of 0 mmHg, 20 mmHg and 40 mmHg. (b) Finite element simulation analysis of corneal von Mises stress distribution and deformation profile of cornea under the IOPs of 0 mmHg, 20 mmHg and 40 mmHg. (c) Strain gauge structure design diagram. (d) Wheatstone bridge schematic diagram. (e) Schematic diagram of contact lens deformation caused by changes in IOP, resulting in changes in the radius of curvature Δr.
Figure 2
Figure 2
Process flow of sensor fabrication.
Figure 3
Figure 3
Physical image of (a) strain gauge and (b) contact lens sensor.
Figure 4
Figure 4
(a) Schematic diagram of the IOP test system. (b) Physical photo of the IOP test system.
Figure 5
Figure 5
The response of the sensor’s output voltage to variations in silicone eyeball pressure.
Figure 6
Figure 6
Dynamic performance of a contact lens sensor on the eyeball model. (a–c) The dynamic cyclic performance of the sensor under different pressures when staying for 0 s, 6 s, and 30 s at the peak, respectively. (d) The dynamic cycle performance of the sensor at different speeds of IOP variation.
Figure 7
Figure 7
(a) Changes in the sensor’s output voltage when the temperature increases from 32 °C to 36 °C. (b) Related measurement error when the temperature increases from 32 °C to 36 °C.
Figure 8
Figure 8
(a) Infrared thermal image of the sensor without current source. (b) Infrared thermal image of the sensor after working for 30 minutes under a 100 μA constant current source.
See this image and copyright information in PMC

References

    1. Tham Y.-C., Li X., Wong T.Y., Quigley H.A., Aung T., Cheng C.-Y. Global prevalence of glaucoma and projections of glaucoma burden through 2040: A systematic review and meta-analysis. Ophthalmology. 2014;121:2081–2090. doi: 10.1016/j.ophtha.2014.05.013. - DOI - PubMed
    1. Weinreb R.N., Khaw P.T. Primary open-angle glaucoma. Lancet. 2004;363:1711–1720. doi: 10.1016/S0140-6736(04)16257-0. - DOI - PubMed
    1. Barkana Y., Anis S., Liebmann J., Tello C., Ritch R.J. Clinical utility of intraocular pressure monitoring outside of normal office hours in patients with glaucoma. Arch. Ophthalmol. 2006;124:793–797. doi: 10.1001/archopht.124.6.793. - DOI - PubMed
    1. Hughes E., Spry P., Diamond J. 24-hour monitoring of intraocular pressure in glaucoma management: A retrospective review. J. Glaucoma. 2003;12:232–236. doi: 10.1097/00061198-200306000-00009. - DOI - PubMed
    1. Yung E., Trubnik V., Katz L.J. An overview of home tonometry and telemetry for intraocular pressure monitoring in humans. Graefe’s Arch. Clin. Exp. Ophthalmol. 2014;252:1179–1188. doi: 10.1007/s00417-014-2668-5. - DOI - PubMed