Initial investigations on systems for measuring intraocular pressure

Schnakenberg, Uwe; Walter, Peter; Bögel, Gerd vom; Krüger, Christopher; Lüdtke-Handjery, H.C; Richter, H. A.; Specht, W; Ruokonen, P.; Mokwa, W.

doi:10.1016/s0924-4247(00)00426-x

Cited by 54 publications

(26 citation statements)

References 7 publications

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“…In order to provide the implant with energy and to read out the measured flow rate, RF passive telemetry is used at a RF frequency of 13.56 MHz (Neukomm et al 2003;Schnakenberg et al 2000). The RF section of the implant is responsible for extracting energy for the implant, for transmitting the level of RF induced voltage to the microcontroller (Silabs C8051F300) as well as for modulating the FSK signal for communication with the external reading unit.…”

Section: Transducer Descriptionmentioning

confidence: 99%

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

Bork¹,

Hogg²,

Lempen

et al. 2010

Biomed Microdevices

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An implantable transducer for monitoring the flow of Cerebrospinal fluid (CSF) for the treatment of hydrocephalus has been developed which is based on measuring the heat dissipation of a local thermal source. The transducer uses passive telemetry at 13.56 MHz for power supply and read out of the measured flow rate. The in vitro performance of the transducer has been characterized using artificial Cerebrospinal Fluid (CSF) with increased protein concentration and artificial CSF with 10% fresh blood. After fresh blood was added to the artificial CSF a reduction of flow rate has been observed in case that the sensitive surface of the flow sensor is close to the sedimented erythrocytes. An increase of flow rate has been observed in case that the sensitive surface is in contact with the remaining plasma/artificial CSF mix above the sediment which can be explained by an asymmetric flow profile caused by the sedimentation of erythrocytes having increased viscosity compared to artificial CSF. After removal of blood from artificial CSF, no drift could be observed in the transducer measurement which could be associated to a deposition of proteins at the sensitive surface walls of the packaged flow transducer. The flow sensor specification requirement of +-10% for a flow range between 2 ml/h and 40 ml/h. could be confirmed at test conditions of 37 degrees C.

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Section: Transducer Descriptionmentioning

confidence: 99%

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

Bork¹,

Hogg²,

Lempen

et al. 2010

Biomed Microdevices

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“…IOL's are universally used to replace the opaque natural lens in cataract surgery, given the large demand for cataract surgery and the usual marked gain in visual function resulting from the procedure, the coupling of an IOP sensor with an IOL implant is an attractive prospect. [1][2][3] The IOL is in direct contact with the aqueous humor inside the anterior chamber providing an accurate measurement of IOP. However, the IOL has size and weight constraints requiring the sensor and inductor to be heavily miniaturized and therefore requiring on-chip circuitry to amplify and process signals (i.e.…”

Section: Introductionmentioning

confidence: 99%

Development of a wireless intra-ocular pressure monitoring system for incorporation into a therapeutic glaucoma drainage implant

Kakaday

Plunkett²,

McInnes

et al. 2008

SPIE Proceedings

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Glaucoma is a common cause of blindness. Wireless, continuous monitoring of intraocular pressure (IOP) is an important, unsolved goal in managing glaucoma. An IOP monitoring system incorporated into a glaucoma drainage implant (GDI) overcomes the design complexity associated with incorporating a similar system in a more confined space within the eye. The device consists of a micro-electro-mechanical systems (MEMS) based capacitive pressure sensor integrated with an inductor printed directly onto a polyimide printed circuit board (PCB). The device is designed to be incorporated onto the external plate of a therapeutic GDI. The resonance frequency changes as a function of IOP, and is tracked remotely using a spectrum analyzer. A theoretical model for the reader antenna was developed to enable maximal inductive coupling with the IOP sensor implant. Pressure chamber tests indicate that the sensor implant has adequate sensitivity in the IOP range with excellent reproducibility over time. Additionally, we show that sensor sensitivity does not change significantly after encapsulation with polydimethylsiloxane (PDMS) to protect the device from fluid environment. In vitro experiments showed that the signal measured wirelessly through sheep corneal and scleral tissue was adequate indicating potential for using the system in human subjects.

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“…As a result, much research has been undertaken, particular in the development of miniaturized wireless systems for pressure measurement. These can be used for the monitoring of intracranial and intraocular pressure, along with the pressure inside many body cavities such as the gastrointestinal and urinary tract [3,4]. This information can be used for clinical studies in areas such as cardiology and pulmonology [5].…”

Section: Introductionmentioning

confidence: 99%

Investigation into the pressure sensing properties of PVDF and PVB thick film capacitors

Arshak

Morris

Arshak

et al. 2006

2006 29th International Spring Seminar on Electronics Technology

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Initial investigations on systems for measuring intraocular pressure

Cited by 54 publications

References 7 publications

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus

Development of a wireless intra-ocular pressure monitoring system for incorporation into a therapeutic glaucoma drainage implant

Investigation into the pressure sensing properties of PVDF and PVB thick film capacitors

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