US3703095A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Applanation tonometer
Assignee: Johns Hopkins University
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Filing: 1970-03-10
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Granted: 1972-11-21
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Expires: 1990-03-10
Abstract
Abstract An electric applanation type tonometer of the all solid state type is provided. A signal null indicative of a desired applanation triggers an electronic switch which takes a reading of a pressure signal. This pressure signal is stored and read out for several minutes after removal of the instrument from the eye.
Inventors
- 👤 Harry F Holcomb
- 👤 Miguel Martinez
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:06
CPC Classifications
A; A61; A61B; A61B3/00; A61B3/10; A61B3/16
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
159 words
An electric applanation tonometer, comprising, a probe having a single electrode disc for mechanically and electrically contacting a patient''s eye by wetting and varying electrical resistance in accordance with the area of said eye contacted, strain gage means, means coupling said disc with said strain gage means and relaying force to said strain gage means of said eye contacted, electrical means for powering said disc and deriving an area signal therefrom, means connectable electrically to another portion of said patient for connecting one side of said disc-powering electrical means to said disc through said patient, electrical means for powering said strain gage means and deriving a force signal therefrom, electrical means for relating said area signal and said force signal, and means for indicating said force signal at a solely desired area signal, said wet contacting disc varying the electrical resistance in accordance with the area of said eye contacted and by control of current flow through said patient.
Claim 2
Dependent Claim
159 words
An electric applanation tonometer, comprising, a probe having a single electrode disc for mechanically and electrically contacting a patient''s eye by wetting and varying electrical resistance in accordance with the area of said eye contacted, strain gage means, means coupling said disc with said strain gage means and relaying force to said strain gage means of said eye contacted, electrical means for powering said disc and deriving an area signal therefrom, means connectable electrically to another portion of said patient for connecting one side of said disc-powering electrical means to said disc through said patient, electrical means for powering said strain gage means and deriving a force signal therefrom, electrical means for relating said area signal and said force signal, and means for indicating said force signal at a solely desired area signal, said wet contacting disc varying the electrical resistance in accordance with the area of said eye contacted and by control of current flow through said patient.
Claim 3
Dependent Claim
159 words
An electric applanation tonometer, comprising, a probe having a single electrode disc for mechanically and electrically contacting a patient''s eye by wetting and varying electrical resistance in accordance with the area of said eye contacted, strain gage means, means coupling said disc with said strain gage means and relaying force to said strain gage means of said eye contacted, electrical means for powering said disc and deriving an area signal therefrom, means connectable electrically to another portion of said patient for connecting one side of said disc-powering electrical means to said disc through said patient, electrical means for powering said strain gage means and deriving a force signal therefrom, electrical means for relating said area signal and said force signal, and means for indicating said force signal at a solely desired area signal, said wet contacting disc varying the electrical resistance in accordance with the area of said eye contacted and by control of current flow through said patient.
Claim 4
Dependent Claim
159 words
An electric applanation tonometer, comprising, a probe having a single electrode disc for mechanically and electrically contacting a patient''s eye by wetting and varying electrical resistance in accordance with the area of said eye contacted, strain gage means, means coupling said disc with said strain gage means and relaying force to said strain gage means of said eye contacted, electrical means for powering said disc and deriving an area signal therefrom, means connectable electrically to another portion of said patient for connecting one side of said disc-powering electrical means to said disc through said patient, electrical means for powering said strain gage means and deriving a force signal therefrom, electrical means for relating said area signal and said force signal, and means for indicating said force signal at a solely desired area signal, said wet contacting disc varying the electrical resistance in accordance with the area of said eye contacted and by control of current flow through said patient.
Claim 5
Dependent Claim
49 words
An electric applanation tonometer as recited in claim 1, wherein said disc is resiliently supported in said probe, and said means for coupling said disc with said strain gage means consists of an elongated plunger adjustable lengthwise for mechanically coupling said resiliently supported disc with said strain gage means.
Claim 6
Dependent Claim
99 words
An electric applanation tonometer as recited in claim 1, wherein said means for powering said disc and deriving an area signal therefrom includes a resistance bridge circuit having an alternating current supply, with said disc, said wetted area and the body of said patient forming one of the resistance arms of said bridge circuit for deriving the area signal from said eye, said alternating current supply supplying current to said bridge so that the varying resistance of said disc, said wetted area and the body of said patient alters the conditions of said bridge to indicate the applanated area.
Claim 7
Dependent Claim
82 words
An electric applanation tonometer as recited in claim 1, wherein said means for powering said strain gage means and deriving a force signal therefrom includes a bridge circuit having a direct current supply, with the strain gage of said strain gage means forming one of the arms thereof for deriving said force signal, said direct current supply supplying current to said bridge so that variations of said strain gage alter the condition of the bridge to indicate variations in the force signal.
Claim 8
Dependent Claim
104 words
An electric applanation tonometer as recited in claim 1, wherein said electrical means for relating said area signal and said force signal includes a semi-conductor switching circuit operable in response to the varying resistance of said disc, said wetted area and the body of said patient and having a triggered semi-conductor stepped generator actuated when said varying resistance reaches a value representative of said desired area thereby controlling the operation of a switchable transistor, with said switchable transistor controlling the path of force signal to the indicating means to indicate the force when the desired area of the eye is contacted by the disc.
Claim 9
Dependent Claim
79 words
An electric applanation tonometer as recited in claim 1, wherein said means for indicating said force signal at a solely desired area signal includes an indicating meter, an amplifier circuit for amplifying said force signal to said indicating meter, and a memory circuit responsive to said force signal for developing a potential level representative of said force signal aNd electrically coupled to said amplifying circuit for holding said potential level representative of said force signal on said indicator meter.
Claim 10
Dependent Claim
99 words
An electric applanation tonometer as recited in claim 2, wherein said means for powering said disc and deriving an area signal therefrom includes a resistance bridge circuit having an alternating current supply with said disc, said wetted area and the body of said patient forming one of the resistance arms of said bridge circuit for deriving the area signal from said eye, said alternating current supply supplying current to said bridge so that the varying resistance of said disc, said wetted area and the body of daid patient alters the conditions of said bridge to indicate the applanated area.
Claim 11
Dependent Claim
82 words
An electric applanation tonometer as recited in claim 7, wherein said means for powering said strain gage means and deriving a force signal therefrom includes a bridge circuit having a direct current supply, with the strain gage of said strain gage means forming one of the arms thereof for deriving said force signal, said direct current supply supplying current to said bridge so that variations of said strain gage alter the condition of the bridge to indicate variations in the force signal.
Claim 12
Dependent Claim
104 words
An electric applanation tonometer as recited in claim 8, wherein said electrical means for relating said area signal and said force signal includes a semi-conductor switching circuit operable in response to the varying resistance of said disc, said wetted area and the body of said patient and having a triggered semi-conductor stepped generator actuated when said varying resistance reaches a value representative of said desired area thereby controlling the operation of a switchable transistor, with said switchable transistor controlling the path of force signal to the indicating means to indicate the force when the desired area of the eye is contacted by the disc.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-11-21 | 1976-05-22 | 1976-11-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-11-21 | 1980-05-22 | 1980-11-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-11-21 | 1984-05-22 | 1984-11-21 | $7700.00 | Window Closed / Lapsed |