Toward a Wirelessly Powered On-Lens Intraocular Pressure Monitoring System

Abstract

This paper presents a wireless on-lens intraocular pressure monitoring system, comprising a capacitance-to-digital converter and a wirelessly powered radio-frequency identification (RFID)-compatible communication system, for sensor control and data communication. The capacitive sensor was embedded on a soft contact lens of 200 μm thickness using commercially available biocompatible lens material, to improve compliance and reduce user discomfort. The sensor chip was shown to achieve effective number of bits greater than 10 over a capacitance range up to 50 pF while consuming only 64-μW power. The on-lens capacitive sensor could detect dielectric variation caused by changes in water content from a distance of 2 cm by using incident power from an RFID reader at 20 dBm. The maximum detectable distance was 11 cm with 30-dBm incident RF power. The rise in eye tissue temperature under 30-dBm RF exposure over an interval of 1 s was simulated and found to be less than 0.01°C.

Electronic Contact Lens: A Platform for Wireless Health Monitoring Applications

“…Consequently, wireless energy harvesting has been considered as an effective approach for contact lenses . Such electronic contact lenses contain a power transfer unit, a read‐out circuit (including the disease‐diagnosing sensor), and encapsulation to avoid direct contact between the electronic devices and the human eye. Such lenses were designed for testing blood glucose using tears.…”

Recent Advances on Implantable Wireless Sensor Networks

“…This disease is the second most common cause of blindness, and it is predicted to affect around 80 million people by 2020 [9]. Different approaches for measuring IOP are possible and range from non-invasive devices, such as contact lenses [10,11] that measure…”

Derzeitiger Stand der elektronischen „kontinuierlichen“ Augendruckmessung

“…Tests mit artifiziellen Druckerhöhungen an einem Silikonmodellauge verliefen mit guter Korrelation zwischen manometrischen und elektronisch gemessenen Werten. Nach demselben Prinzip wurde von Chiou et al [45] eine Kontaktlinse mit kapazitivem Sensor und 200 µm Dicke entwickelt, bei der die Daten ebenso kabellos übertragen werden. Der Datenleser befand sich in einer zu tragenden Brille (in der Nacht während des Schlafes wahrscheinlich unpraktisch).…”

“…Langzeitergebnisse betreffend die okuläre Toleranz dieser implantierten Medizinprodukte fehlen (noch). Der kabellose Datentransfer braucht viel Leistung (Energieumsatz pro Zeitspanne, mindestens 1 mW [45] und kann theoretisch thermische Alterationen bewirken. Deshalb wird nicht kontinuierlich gemessen, sondern zu willkürlich ausgesuchten Zeitpunkten.…”