Normally, intraocular pressure (IOP) exhibits a significant circadian rhythm, typically peaking in the early morning hours before the end of sleep (3–4 mmHg higher than daytime levels), with a trough occurring at the end of the day. This phenomenon is closely associated with changes in body position (supine posture increases episcleral venous pressure by 3–6 mmHg) and fluctuations in glucocorticoid levels.
Furthermore, frequent eye movements during sleep, such as those occurring during rapid eye movement (REM) sleep, can increase resistance to aqueous humor outflow. This is particularly concerning in patients with angle-closure glaucoma, where the risk of acute attacks is 3–5 times higher at night compared to during the day.
Smart contact lenses have emerged as a promising solution for continuous, noninvasive ocular signal monitoring instead of discrete measurements.
While Goldman Appalanation Tonography (GAT) is the ideal method, it requires topical anesthesia and fluorescein instillation before measurement, and the fluorescein concentration can influence accuracy. Furthermore, GAT-like instruments often require a slit lamp examination. Corneal thickness, stiffness, and tear film characteristics can also introduce measurement errors.
Contact lenses are a practical solution to the problems of continuous monitoring. Gan and colleagues have proposed a stretchable self-decoupled BCL comprising electromagnetic capacitive IOP (CIOP) and neodymium-iron-boron (NdFeB)-MEM components. The design features an NdFeB/polydimethylsiloxane (PDMS) interlayer film that separates double-layered serpentine-geometry spiral copper (Cu) films.
This innovation involves a stretchable bimodal contact lens (BCL) amalgamating self-decoupled electromagnetic capacitive intraocular pressure (CIOP) and magnetic eye movement (MEM) monitoring components. This integrated system offers a non-invasive and comfortable solution for real-time eye health monitoring, providing accurate measurements and continuous tracking of eye status.
In this way, both IOP and EM can be monitored continuously through closed lids.
REFERENCE:
Gan, X., Yao, G., Li, C. et al. Closed-eye intraocular pressure and eye movement monitoring via a stretchable bimodal contact lens. Microsyst Nanoeng 11, 83 (2025). https://doi.org/10.1038/s41378-025-00946-y
