In-vitro Calibration Of An Ophthalmic Analyte Sensor

• US 20140107447A1
• Filed: 10/12/2012
• Published: 04/17/2014
• Est. Priority Date: 10/12/2012
• Status: Abandoned Application

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Liu, Zenghe, Otis, Brian
• Application Number:
  US13/650,248
• Publication Number:
  US 20140107447A1
• Time in Patent Office: Days
• US Class Current: 600/347
• CPC Class Codes: A61B 5/0004 characterised by the type of physiological signal transmitted
• CPC Class Codes: A61B 5/0026 characterised by the transmission medium
• CPC Class Codes: A61B 5/14507 specially adapted for measuring characteristics of body fluids other than blood devices for taking samples of body liquids A61B10/0045
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/6821 Eye
• CPC Class Codes: A61B 5/683 Means for maintaining contact with the body A61B5/6802 takes precedence

Abstract

An eye-mountable device includes an electrochemical sensor embedded in a polymeric material configured for mounting to a surface of an eye. The electrochemical sensor includes a working electrode, a reference electrode, and a reagent that selectively reacts with an analyte to generate a sensor measurement related to a concentration of the analyte in a fluid to which the eye-mountable device is exposed. A calibration-solution measurement is obtained while the eye-mountable device is exposed to a calibration solution. A calibration value is determined based on at least the calibration-solution measurement and an analyte concentration of the calibration solution. A tear-film measurement is obtained while the eye-mountable device is mounted to an eye so as to be exposed to tear film. The analyte concentration of the tear film is determined based on at least the tear-film measurement and the calibration value.

Claims

1. A method comprising:

receiving an indication of a calibration-solution sensor measurement obtained from an eye-mountable device exposed to a calibration solution, wherein the eye-mountable device includes an electrochemical sensor with a working electrode, a reference electrode, and a reagent that selectively reacts with an analyte, and wherein the eye-mountable device is configured to obtain a sensor measurement related to a concentration of the analyte in a fluid to which the eye-mountable device is exposed;

determining a calibration value based on at least the calibration-solution measurement and an analyte concentration of the calibration solution;

receiving an indication of a tear-film sensor measurement obtained from the eye-mountable device exposed to tear film; and

determining a concentration of the analyte in the tear film based on at least the tear-film sensor measurement and the calibration value.

2. The method according to claim 1, further comprising:

receiving a calibration mode input via a user interface; and

wherein the receiving the indication of the calibration-solution sensor measurement is responsive to the receiving the calibration mode input.

3. The method according to claim 1, further comprising:

receiving an additional calibration-solution sensor measurement obtained with the eye-mountable device exposed to an additional calibration solution; and

determining an additional calibration value based on at least the additional calibration-solution sensor measurement and an analyte concentration of the additional calibration solution;

4. The method according to claim 3, further comprising:

receiving an indication of an additional tear-film sensor measurement obtained from the eye-mountable device exposed to tear film; and

determining a concentration of the analyte in the tear film based on at least the additional tear-film sensor measurement and the additional calibration value.

5. The method according to claim 1, further comprising:

interrogating the eye-mountable device to obtain the calibration-solution sensor measurement while the eye-mountable device is exposed to the calibration solution by transmitting radio frequency radiation to power the electrochemical sensor with energy harvested from the radiation sufficient to;

(i) apply a voltage between the working electrode and the reference electrode sufficient to cause electrochemical reactions at the working electrode to thereby generate a calibration-solution amperometric current;

(ii) measure the calibration-solution amperometric current; and

(iii) modulate a backscatter radiation response of the eye-mountable device based on the measured calibration-solution amperometric current; and

wherein the receiving the indication of the calibration-solution sensor measurement includes, responsive to the interrogating the eye-mountable device to obtain the calibration-solution sensor measurement, receiving backscatter radiation from the eye-mountable device modulated based on the measured calibration-solution amperometric current.

6. The method according to claim 5, further comprising:

interrogating the eye-mountable device to obtain the tear-film sensor measurement while the eye-mountable device is exposed to the tear film by transmitting radio frequency radiation to power the electrochemical sensor with energy harvested from the radiation sufficient to;

(i) apply a voltage between the working electrode and the reference electrode sufficient to cause electrochemical reactions at the working electrode and thereby generate a tear-film amperometric current;

(ii) measure the tear-film amperometric current; and

(iii) modulate a backscatter radiation response of the eye-mountable device based on the measured tear-film amperometric current; and

wherein the receiving the indication of the tear-film sensor measurement includes, responsive to the interrogating the eye-mountable device to obtain the tear-film sensor measurement, receiving backscatter radiation from the eye-mountable device modulated based on the measured tear-film amperometric current.

7. The method according to claim 1, wherein the calibration value corresponds to a slope in a linear function relating measurements from the electrochemical sensor to analyte concentration levels.

8. The method according to claim 1, wherein the calibration value corresponds to an intercept in a linear function relating measurements from the electrochemical sensor to analyte concentration levels.

9. A system comprising:

an eye-mountable device comprising;

a transparent polymeric material having a concave surface and a convex surface, wherein the concave surface is configured to be removably mounted over a corneal surface and the convex surface is configured to be compatible with eyelid motion when the concave surface is so mounted;

an antenna;

an electrochemical sensor that includes a working electrode, a reference electrode, and a reagent that selectively reacts with an analyte;

a controller electrically connected to the electrochemical sensor and the antenna, wherein the controller is configured to (i) control the electrochemical sensor to obtain a sensor measurement related to a concentration of the analyte in a fluid to which the eye-mountable device is exposed and (ii) use the antenna to indicate the sensor measurement; and

a reader operable in a calibration mode and a measurement mode,

wherein in the calibration mode the reader is configured to (i) wirelessly communicate with the antenna to receive a calibration-solution sensor measurement obtained with the eye-mountable device exposed to a calibration solution, (ii) determine a calibration value based on at least the calibration-solution sensor measurement and an analyte concentration of the calibration solution, and (iii) store the calibration value in a memory, and

wherein in the measurement mode the reader is configured to (i) wirelessly communicate with the antenna to receive a tear-film sensor measurement obtained with the eye-mountable device exposed to a tear film and (ii) determine a concentration of the analyte in the tear film based on at least the tear-film sensor measurement and the calibration value.

10. The system according to claim 9, wherein the reader is further configured to supply power to the eye-mountable device through the antenna.

11. The system according to claim 9, wherein the reader comprises a user interface for selecting between the calibration mode and the monitoring mode.

12. The system according to claim 9, wherein in the calibration mode the reader is further configured to:

(i) wirelessly communicate with the antenna to receive an additional calibration-solution sensor measurement obtained with the eye-mountable device exposed to an additional calibration solution, (ii) determine an additional calibration value based on at least the additional calibration-solution sensor measurement and an analyte concentration of the additional calibration solution, and (iii) store the additional calibration value in the memory.

13. The system according to claim 12, wherein the reader is configured to determine both the calibration value and the additional calibration value based on at least the calibration-solution sensor measurement, the additional calibration-solution sensor measurement, and the analyte concentrations of the calibration solution and the additional calibration solution, and wherein in the measuring mode the reader is configured to determine the concentration of the analyte in the tear film based on at least the tear-film sensor measurement, the calibration value, and the additional calibration value.

14. The system according to claim 9, wherein the calibration value corresponds to a slope in a linear function relating measurements from the electrochemical sensor to analyte concentration levels.

15. The system according to claim 9, wherein the calibration value corresponds to an intercept in a linear function relating measurements from the electrochemical sensor to analyte concentration levels.

16. The system according to claim 9, wherein the analyte is glucose and the reagent comprises glucose oxidase.

17. The system according to claim 9, wherein the electrochemical sensor is embedded in the transparent polymeric material such that the analyte reacts with the reagent after diffusing through the transparent polymeric material.

18. A non-transitory computer readable medium storing instructions that, when executed by one or more processors in a computing device, cause the computing device to perform operations, the operations comprising:

receiving an indication of a calibration-solution sensor measurement obtained from an eye-mountable device exposed to a calibration solution, wherein the eye-mountable device includes an electrochemical sensor with a working electrode, a reference electrode, and a reagent that selectively reacts with an analyte, and wherein the eye-mountable device is configured to obtain a sensor measurement related to a concentration of the analyte in a fluid to which the eye-mountable device is exposed;

determining a calibration value based on at least the calibration-solution measurement and an analyte concentration of the calibration solution;

receiving an indication of a tear-film sensor measurement obtained from the eye-mountable device exposed to tear film; and

determining a concentration of the analyte in the tear film based on at least the tear-film sensor measurement and the calibration value.

19. The non-transitory computer readable medium according to claim 18, wherein the operations further comprise:

receiving a calibration mode input via a user interface, and wherein the receiving the indication of the calibration-solution sensor measurement is carried out responsive to the receiving the calibration mode input.

20. The non-transitory computer readable medium according to claim 18, wherein the operations further comprise:

receiving an additional calibration-solution sensor measurement obtained with the eye-mountable device exposed to an additional calibration solution; and

determining an additional calibration value based on at least the additional calibration-solution sensor measurement and an analyte concentration of the additional calibration solution;