Contoured facial mask with multiple contact probes for use with tactile tonometer
View Patent ↗A system for measuring intraocular pressure (IOP) of an eye, comprising a plurality of force sensors that are adapted to contact a surface of an eye, measuring the forces exerted on the force sensors when in contact with the eye surface, and processing the measured forces to determine the 10P of the eye as a function of the measured forces.
1. A system for measuring intraocular pressure (IOP) of a subject's eye, comprising:
a plurality of force sensors, said force sensors being adapted to contact a surface of the subject's eye via moveable probes;
an advancing device for advancing said force sensors towards the subject's eye in a controlled fashion;
a measuring device for measuring forces being exerted on said force sensors when said force sensors are in contact with the subject's eye surface; and
a processor adapted to receive said measured forces and programmed to determine intraocular pressure (IOP) of the subject's eye as a function of said measured forces, wherein said IOP of the subject's eye is determined by finding intercepts of force curves with either vertical or horizontal axes, where a distance of said intercepts is proportional to intraocular pressure and an offset between the two force probes via the following relationship
p
=
d
2
kZ
F
E
c
[
mm
Hg
]
where:
p is the IOP value, and
d represents a horizontal distance and Z represents a vertical distance, respectively, between the force probes,
k is a calibration stiffness coefficient with units of mm 2 , and
F E c is the distance from the intercepts to the origin of the plot where both forces are zero.
2. The system of claim 1 , wherein said system includes a linear force sensor transmitter that is adapted to extend and retract each of said force sensors.
3. The system of claim 2 , wherein said linear force sensor transmitter is further adapted to secure said force sensors in extended and retracted positions.
4. The system of claim 1 , wherein said force sensors include a plurality of different length rods.
5. The system of claim 4 , wherein a distal end of at least one of said rods is contoured to approximate a shape of the subject's eye.
6. The system of claim 4 , wherein a distal end of one of said rods extends beyond distal ends of the other rods.
7. The system of claim 1 , wherein said advancing device includes a spring.
8. The system of claim 1 , wherein said advancing device includes resiliently deformable foam.
9. A method for measuring intraocular pressure IOP of a subject's eye, comprising the steps of:
providing a palpation system as claimed in claim 1 , having first and second force sensors with a known Z/d offset ratio. said force sensors being adapted to contact a surface of the subject's eye, where the first force sensor contacts the subject's eye first followed by the second sensor,
measuring forces exerted on said first and second force sensors when said first and second force sensors are in contact with the subject's eye surface, and processing said measured forces;
applying a gradual force to the subject's eye surface with said palpation system and measuring force exerted on said first and second force sensors until both force sensors measure non-zero force;
determining a force value of said first force sensor when said second sensor contacts the subject's eye and registers a first non-zero force, and
determining a calibration stiffness coefficient k calibration coefficient from
2 k=F E1 c /p d 1 /Z 1 ,
where:
p is the IOP value, and
d represents a horizontal distance and Z represents a vertical distance, respectively, between the force probes,
F E c is the measured force value of said first sensor when said second sensor contacted the subject's eye.
10. The method of claim 9 , where said first and second force probes have different known Z/d ratios, whereby the resulting force curves are interpreted as if obtained at different pressures.
11. The system of claim 1 , wherein the moveable probes are contained in a facial mask.
12. The method of claim 10 , wherein the fore curve from the force pair Z/d, is interpreted as a force curve obtained from the first pair Z 1 /d 1 , but under pressure p 2 =p, Z 2 d 1 /d 2 Z 1 .
13. A system for measuring intraocular pressure (IOP) of a subject's eye, comprising:
a plurality of force sensors, said force sensors being adapted to contact a surface of the subject's eye via moveable probes contained in a facial mask;
an advancing device for advancing said force sensors towards the subject's eye in a controlled fashion;
a measuring device for measuring forces being exerted on said force sensors when said force sensors are in contact with the subject's eye surface; and
a processor adapted to receive said measured forces and programmed to determine intraocular pressure (IOP) of the subject's eye as a function of said measured forces, wherein said IOP of the subject eye is determined by finding intercepts of force curves with either vertical or horizontal axes, where a distance of said intercept is proportional to intraocular pressure and an offset between the two force probes via the following relationship
p
=
d
2
k
Z
F
E
c
[
mmHg
]
where:
p is the IOP value, and
d represents a horizontal distance and Z represents a vertical distance, respectively between the force probes,
k is a calibration stiffness coefficient with units of mm 2 , and
F c E is the distance from the intercepts to the origin of the plot where both forces are zero, wherein said mask has a plurality of inflatable bags for custom fitting the mask to conform to a facial anatomy of the subject.
14. The system of claim 13 , wherein the advancing device includes a spring or resiliently deformable foam.
15. The system of claim 13 , wherein said system includes a linear force sensor transmitter that is adapted to extend and retract each of said force sensors.
16. The system of claim 13 , wherein said linear force sensor transmitter is further adapted to secure said force sensors in extended and retracted positions.
17. The system of claim 13 , wherein said force sensors include a plurality of different length rods.
18. The system of claim 17 , wherein a distal end of at least one of said rods is contoured to approximate a shape of the subject's eye.
19. The system of claim 17 , wherein a distal end of one of said rods extends beyond distal ends of the other rods.