A Wireless, Implantable Intra- Ocular Pressure Sensor for the Management of Glaucoma Gabriel Simon, M.D. Ph.D. Sept 16, 2008 ESCRS.

A Wireless, Implantable Intra-Ocular Pressure Sensor for the

Management of Glaucoma

Gabriel Simon, M.D. Ph.D.Sept 16, 2008

ESCRS

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Current IOP MeasurementsCurrent Methods of IOP Measurement Applanation Tonometer (Goldmann)

• Requires contact with eye surface• Errors due to corneal thickness, past surgeries, etc..• Clinical & limited home use

Dynamic Contour Tonometry (PASCAL DCT)• Relies on contour matching• More accurate than applanation tonometers• Clinical use only

Electronic Indentation Tonometer (Tono-Pen)• Limited accuracy• Home and clinical use

No method for continuous, remote IOP monitoring currently exists Continuous monitoring will allow complete glaucoma management

RF Transmission of Data & Power Current range exceeds 3 meters

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Background – IOP Monitoring

Current Approach – Reactive Sample every 3-6 months Tonometer measurement, clinic-based

• Corneal thickness-induced errors

IOP Fluctuations can vary over 24-hour period Diurnal variations in IOP (2008 Sit, et al.) Circadian/Hourly fluctuations (2006 Barkana, et al.)

Continuous IOP Monitoring – Managing IOP Sample continuously, with daily upload Accurate to 0.5 mmHg Ophthamologist can monitor IOP trends daily Requires:

• Wireless, high-sensitivity sensor• Ultra-low power circuitry• Miniature packaging (<5mm per side) for implantation• External RF-charging and data collection device

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Implantable Sensor Concept

Implantable sensor for continuous patient monitoring Prototyped at Purdue Brain-Computer Interface (BCI) Lab Implanted in anterior chamber or

suprachoroidal space • 300µm overall thickness

Capacitive Sensor• 0-50mmHg sensitivity• 0.5mmHg accuracy

Amplifier and Telemetry• Capture IOP every 5 minutes• RF download and recharge

External Unit• Stores & transmits all IOP data• Held to eye for <10 seconds

Provides significant improvement in quality of care

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IOP Sensor Device

Remote patient monitoring Provides near-continuous IOP data on daily basis

• Disease progression & drug monitoring Continuously sampled IOP data evaluated daily

• Email or internet interface, Bluetooth compatible E-consultation if necessary Minimize cost & time while improving

quality of care• Daily reports of IOP vs. sporadic visits

Patient and Doctor Interface Promotes patient compliance Easy to use for physicians

• IOP trends and warnings based on relevant information

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Intra-Ocular Pressure Sensor Design

Research partners: Gabriel Simon2, Babak Ziaie3, SOLX4

2Professor of Ophthalmology, Boston University3Associate Professor, Department of Electrical Engineering, Purdue University

4Boston University startup company

Wireless data module

LPF

mixer LNA

VCO

antenna

S1

S2

VoltageregulatorBattery

Biasingcircuit

Powering module

External receiver withgraphical user interface

and power-couplinghardware

1) Amplifying module

2) Wireless data module

3) IOP sensing module

4) Powering module

5) External user interface

IOP sensing module

amp

Amplifying module

Clk

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IOP Sensor Concept – Location

Suprachoroidal Implant Sensor surface protrudes into Anterior Chamber

• IOP measured in AC 15-minute implant procedure Posterior Chamber: same as IOL procedure Similar to gold shunt/suprachoroidal procedure Minimal, transient complications

Posterior Chamber Implant Same as IOL procedure No learning curve 5-10 minute procedure

Candidate patients Glaucoma patients Cataract - IOL patients

• Does not preclude later IOL implant

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Implant Prototypes and Materials

Silicon substrate

Implant materials: Low-Temperature

Co-fired Ceramic (LTCC) Silicon PMMA Liquid-Crystal

Polymer (LCP)

LTTC substrate

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Posterior Chamber Sensor Implant

PMMA or Liquid-Crystal Polymer (LCP) substrate

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Wireless Power Transmission

Initial studies show that we can achieve low-power RF transmission from a miniature implantable device for ocular implant applications. In-vivo experiments show that the implant was measured to have a sufficient signal-to-noise ratio margin for high data-rate transmission, validating this approach for intra-ocular pressure telemetry.

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Wireless Transmission - Testing

The power received is at least 10 dB greater than the MDS (minimum detectable signal) and we can achieve successful wireless data transfer. LTCC based loop antennas provide less attenuation caused by tissues after implanting than the silicon based monopole antennas.

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IOP Sensor Data Management

Data Collection Patient recharges & uploads once/day Data Hub at patient’s residence Relies on PC with modem, phone line, or cell phone

Data Management Multi-user, web-based database server HIPAA compliant, with backup security Allows multi-point access via internet

Clinical Data Analysis Patient information provided to clinician via internet UI

• IOP summary trends• Medication compliance• Capable of supporting additional physiological data capture

Presented to clinician in simple overview• 1-5 minutes of review per patient

24-7 access to database with subscription

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Summary and Future Studies

Continuous, wireless IOP sensor will provide a new level of glaucoma management Remote patient monitoring via internet Improved treatment, compliance, and outcomes Reduced office visits and cost-to-treat

Future: Combination diagnostic and treatment Passive suprachoroidal sensor with

shunting capabilities• flow channels incorporated into sensor

package Active suprachoroidal glaucoma manage-

ment device• Remote IOP monitoring capability• Adjustable flow resistance

– Wireless adjustment of outflow facility– Based on IOP signal from sensor– Remote adjustment via external charging device

Aqueous Outflow