Tonometer
First Claim
1. An applanation tonometer, for measuring pressure within a human eye, the tonometer comprising:
- a main body, which is generally tubular, defines a bore and includes a portion bearing a scale;
a plunger slidably mounted within the bore of the main body, extending outwardly from a first end of the main body and including a head at one end for contacting an eyelid and the other end of the plunger being retained within the main body, the head being sufficiently large that, in use, an eyeball is flattened and subject to applanation;
spring biasing means acting between the plunger and the main body, biasing the head away from the main body; and
a marker member frictionally retained within the bore of the body for displacement relative to the scale by the plunger, to indicate a maximum load applied to the plunger, wherein the scale bearing portion of the body includes viewing means permitting the location of the marker member relative to the scale to be viewed from the exterior, and wherein the scale means is the only means in the apparatus for measuring a characteristic of the eye.
1 Assignment
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Accused Products
Abstract
A tonometer, for determining intraocular pressure, has a body, which can be a transparent, substantially tubular body. A plunger is located within the body and a coil spring acts between the body and the plunger. A marker member is frictionally retained within the body and is displaced relative to an external scale on the body. In use, the tonometer is brought up against the eyelid of a closed eye and the body displaced relative to the head of the plunger, until the pressure is sufficient to create a pressure phosphene. The device is then removed and the displacement of the marker member, indicative of the applied pressure is read. This reading corresponds to the intraocular pressure. The device may include a return member for returning the marker member to a zero or rest position
18 Citations
29 Claims
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1. An applanation tonometer, for measuring pressure within a human eye, the tonometer comprising:
- a main body, which is generally tubular, defines a bore and includes a portion bearing a scale;
a plunger slidably mounted within the bore of the main body, extending outwardly from a first end of the main body and including a head at one end for contacting an eyelid and the other end of the plunger being retained within the main body, the head being sufficiently large that, in use, an eyeball is flattened and subject to applanation;
spring biasing means acting between the plunger and the main body, biasing the head away from the main body; and
a marker member frictionally retained within the bore of the body for displacement relative to the scale by the plunger, to indicate a maximum load applied to the plunger, wherein the scale bearing portion of the body includes viewing means permitting the location of the marker member relative to the scale to be viewed from the exterior, and wherein the scale means is the only means in the apparatus for measuring a characteristic of the eye. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- a main body, which is generally tubular, defines a bore and includes a portion bearing a scale;
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17. A method of diagnosing the presence of abnormal pressure within an eyeball of a subject, the method comprising the steps of:
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(1) providing a tonometer, for measuring pressure within a human eye, the tonometer including a head at one end for contacting an eyelid, the head being sufficiently large to cause, in use, flattening and applanation of an eyeball, and indication means for indicating a maximum load applied to the head;
(2) placing the tonometer on one eyelid and pressing the tonometer against the eyelid, so as to apply pressure through the head of the tonometer and the eyelid to the eyeball causing applanation of the eyeball;
(3) when the subject notices a pressure phosphene, terminating displacement of the body, noting the maximum load indicated by the indication means and removing the tonometer; and
(4) determining the pressure within the eyeball from the maximum load indicated by the indication means when the pressure phosphene is detected. - View Dependent Claims (18, 20, 21, 22)
(i) ensuring that the marker member is initially located adjacent the zero position on the scale;
(ii) after the subject notices a pressure phosphene, reading the location of the marker member relative to the scale.
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20. A method as claimed in claim 18, which includes the following additional step:
(iii) subsequently returning the marker member to the zero position.
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21. A method as claimed in claim 20, wherein the tonometer includes a return member slidably mounted within the bore of the body and extending through the other end of the bore, wherein step (iii) comprises displacing the return member to displace the marker member to the zero position.
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22. A method as claimed in claim 20 or 21 which comprises applying the head of the tonometer to an upper medial aspect of the eye, away from the cornea.
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19. A method as claimed in any one of claims to 18, which includes determining the intraocular pressure from the load applied.
- 23. A method of obtaining information concerning the pressure within the eyeball of a subject, the method comprising the step of determining the load on an eyeball when a pressure phosphene is detected by the subject.
Specification