HK1021498B - Tonometer - Google Patents

Description

Tonometer

Technical Field

The present invention relates to an apparatus and method for measuring intraocular pressure in a human eye. The invention is particularly concerned with tonometers for measuring the applanation of the cornea of a human eye.

Background

It is now known that glaucoma, an ocular disease, is formed by excessive human eye pressure. The disease accounts for a large proportion of blindness. Studies have shown that the disease is found and present in a large number of people, particularly over 40 years old, with some more people over 50 years old.

It is also known that glaucoma can be detected at an early stage, thereby preventing damage to the eyes and blindness. Appropriate treatment and care can arrest the progression of the disease and preserve useful vision.

Since glaucoma is widespread, many people need to measure internal eye pressure, there are many sophisticated instruments, they are expensive, and they require a complex medical site to operate. Typically, such instruments apply a force to the eyeball in an amount sufficient to flatten the surface of the eye (applanation of the cornea) or to indent (concavity) for measurement. The amount of force required to achieve a certain flattening or collapse is related to the intraocular pressure measured internally, usually expressed as mm mercury.

Typically, the medical instruments involved have some sort of applanation or depression applied directly to the cornea of an open eye to measure the corneal applanation or depression. In the case of natural human response, this requires local anesthesia. The equipment is complex and expensive and requires highly trained technicians to operate it. Other proposals have been made, to the best of the applicant's knowledge, the following patents: us patent 1637421; 1661918, 2656715; 5176139 and 5197473; french patent 2542603, russian patent 2004187 and 457466.

Lipschutz, U.S. patent 1637421, is a pressure indicator that is not related to measuring eye pressure, but is related to pressurizing other parts of the body. It is based on a phenomenon known to be sensitive to pressure in a part of the body, indicating illness. In particular, it is based on the fact that the progression of the disease is related to the sensitivity of the corresponding region of the body. To this end, it provides a device which is able to measure the pressure applied to a particular area, relating this pressure to the progression of the disease. No explicit indication is given of the use of this technique on the human eye. Measuring the stress of the human eye is a unique and difficult problem compared to measuring other parts. Since the human eye is sensitive and delicate, if one attempts to reach the eye, everyone has a strong natural reaction of closing the eye. The Lipschutz patent does not mention this.

An edge-related patent 1661718 discloses a hardness testing device.

An eye tension indicator is disclosed in U.S. patent 2656715 to Tolman. However, this requires contact with the eyeball. It relies on the known relative displacement of various components to measure intraocular pressure and also appears to be a complex and delicate instrument. It cannot be used outside the medical site because it must be in contact with the naked eye.

Two U.S. patents 5176139 and 5197473 to Fedorov disclose a tonometer and related method. It employs a slightly unique technique in which a ball is allowed to freely fall onto the cornea covered by the eyelid. The function of the ball is to deform the cornea, and the amount of rebound of the ball is determined by the rebound height of the ball, depending on the magnitude of the intraocular pressure. This technique appears to be difficult to implement because it depends on judging the rebound height of the ball.

Russian patent 457466 discloses an intraocular pressure sensor. It employs a hall effect sensor. The weight determines the penetration force of a plunger whose displacement is conducted by a hall effect sensor, the output of which is proportional to the displacement. Russian patent 2004187 discloses a tonometer having a hollow cylindrical body with a top and a working end face. But it is unclear how this device works. In any case, it is applied to the eyeball of the naked eye, or local anesthesia is performed in the medical site.

One problem with measuring intraocular pressure today is that intraocular pressure changes day to day and even every hour. It is therefore highly desirable to provide a simple and inexpensive technique for measuring this pressure. This technique allows an average person to measure the pressure of their eyes without the need for complex, expensive equipment, the need to visit a medical facility, and the need to spend time on highly trained medical personnel.

Summary of The Invention

According to a first aspect of the present invention there is provided a applanation tonometer for measuring pressure within an eye, comprising: a body, generally tubular, defining an aperture and including a graduated portion; a plunger slidably mounted within the bore of the body and including a head, one end of the plunger being in contact with the eyelid and the other end remaining within the body, the head being sufficiently large to flatten the eyeball and create a flattened cornea when in use; a spring-loaded device acts between the plunger and the body to urge the head away from the body, and the flag member is frictionally retained in the bore of the body and is moved by the plunger relative to the sliding scale to indicate the maximum load applied to the plunger, wherein the scale comprises a visual member allowing the position of the flag member relative to the scale to be externally visible.

The body preferably includes a first radially inwardly extending flange member adjacent the first end of the plunger and a first radially outwardly extending nose member at the other end of the plunger, the first flange member and the first nose member being dimensioned to retain the other end of the plunger within the body.

The body is generally elongate and is moulded from a transparent material.

The tonometer preferably includes a return member slidably mounted in the aperture and extending from the second end of the body, the return member enabling the user to move the marker member.

In accordance with another aspect of the present invention,provides a method for obtaining the intraocular pressure condition of a subject In the method, the raw materials are mixed,the method comprises the following steps:

(1) providing a tonometer for measuring pressure in a human eye, the tonometer comprising:one end contact A head of an eyelid large enough to flatten or flatten the eyeball in use; and instructions are added to the head An upper maximum load indicating device;

(2) placing the tonometer on the eyelid and pressurizing the tonometer as the subject's eye closes Resting on the eyelid, such that the eyeball is flattened by the head of the tonometer and the eyelid pressurizing the eyeball;

(3) when the subject perceives a pressure oculoplasia (prossure phosphohene), the eye drops Stopping the main body from moving, recording the maximum load indicated by the indicating device, and removing the tonometer;

(4) pressure sensed from the indicating meansMaximum load in the case of a flash of the eye, determining the intraocular pressure And (4) pressure.

The method can include the additional steps of:

(5) returning the flag member to the null position.

Pressure-contact flashes are distinct bright spots or glows, or arcs, that are detected by the subject.

Preferably, the tonometer includes a return member slidably mounted in the main body aperture and extending from the other end of the aperture, and step (5) then includes movement of the return member to move the marker member to the null position.

Brief description of the drawings

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show a preferred embodiment of the invention, and in which:

FIG. 1 is a side and partial cross-sectional view of a first embodiment of a tonometer in use;

FIG. 2 is a perspective view of a tonometer according to a second embodiment of the invention;

FIG. 3 is a plan view of the tonometer of FIG. 2;

FIG. 4 is a view taken along line IV-IV of FIG. 3;

FIG. 5 is a view taken along the line V-V of FIG. 4;

fig. 6 is a view in the direction of arrow VI of fig. 3.

Description of the preferred embodiments

A flattened tonometer in a first embodiment of the invention is generally indicated at 10 in the drawings. Tonometer 10 has a main body or cover 12. The body is substantially tubular and is adapted to be held by a user. For this purpose, it can comprise a special part moulded or shaped to ensure grip.

The right end of the body 12 in the illustration includes an inwardly turned flange 14 for retaining the plunger as will be described in detail below. There is also an outwardly extending flange 16 for holding the device against the user's eye, as will be described in more detail below.

At the left end of the body 12 as viewed in the drawings, a second inwardly extending flange 18 is included.

On the outside of the body there is a scale 20 with numerical markings to indicate the force applied by the device. At least this portion of the body 12 should be a uniform segment, and it is not important whether the entire outer portion of the body 12 is a uniform segment.

The body 12 defines an internal bore 22. As can be seen, the body 12 should have a constant cross-section at least at the scale 20, so that at this location the bore 22 also has a constant cross-section. Here the marker member 24 is slidably mounted within the bore 22. It is made of an elastomeric material and is sized to fit slightly snugly within the bore 22 so as to be frictionally retained within the bore 22. The marking member 24 should be sized to move freely while remaining securely in any position within the bore 22 as the plunger moves it, as will be described in more detail below. In particular, the force required to overcome the frictional force of the marking member 24 should not be great enough to affect the force at which a reading is taken. In addition, at least the scale portion 20 of the body 12 must be transparent or partially transparent so that the position of the marking member 24 can be seen.

Extending from the body 12 is a plunger or contact member 26. The plunger includes a shaft 28, an annular retaining guard 30 and a head 32. The head or contact member 32 may have many shapes and preferably has a flat disc surface 34, and the configuration shown on the left in the drawings is not critical.

Both the nose 30 and the flange 14 are generally annular, with the annular nose 30 being sized to have a diameter slightly larger than the inner diameter of the flange 14. The difference is sufficiently small that tonometer 10 can be assembled by simply pressing nose 30 over flange 14. To this end, the end of the body 12 adjacent the flange 14 has two or more axially extending slots to allow the right end portion of the body 12 to be easily moved. Accordingly, the nose 30 can have a tapered surface 38 for abutment with the flange and a flat surface 40 for abutment with the flange 14 when assembled, as shown.

A ballast coil spring 36 is mounted about the shaft 28. One end of which abuts the outside of the flange 14 and the other end of which abuts one side of the head 32. The spring 36 is of variable size and is not immediately compressed after assembly, and it has a certain amount of slack. This returns the marker member 24 to the vicinity of the zero point on the scale 20, as will be described in more detail below. The force to move the flag member 24 is much less than any load applied by the spring 36. The load on the head 32 is then only spring loaded when moving the marker member 24.

The inner end 42 of the plunger 26 is now a flat surface adapted to abut the flag member 24 and move it without attaching to it. To move the marking member 24 from another aspect, a return member is provided. The return member has an annular retaining nose 46 which interacts with the flange 18 substantially as in the case of the flange 14 and the nose 30. The left end of the body 12 is also shown to facilitate engagement with the return member 44. The return member 44 has an abutment surface 48 that moves the marker member 24. It is also freely slidably mounted within the body 12. It may also optionally provide a spring 49. So that it remains in the extended position.

In use, it is first confirmed that the marking member 24 is located near the zero point of the scale 20. If desired, the return member 44 is moved into the body 12, pushing the marking member to this position.

The head 32 is then placed against the eyelid 50 closing the eye. The head 32 is applied to the upper central region of the eye away from the cornea. This is done by the subject or user turning the eye up and down slightly. This most convenient area varies from person to person. The user simply grasps body 12 and places end surface 34 on eyelid 50. When surface 34 abuts eyelid 50, body 12 is moved toward eyelid 50 and the user can press the flange 16 with a finger if desired. This movement drives the plunger into the body 12, moving the marking member 24 along the scale 20. This increases the load that the spring 28 places on the head 32.

This movement is continued, increasing the pressure on the head until the user perceives in his eye a bright spot or glow, or arc, of a known pressure tamponade flash. The user then stops moving body 12 and removes tonometer 10 from the eye. The spring 28 then pushes the plunger 26 out of the body 12. However, the marking member 24 will be frictionally held in a certain position on the scale 20. This position will show the load or force when a pressure eye flash occurs. This shows intraocular pressure.

A direct pressure reading can be shown on scale 20 or the user can use a table corresponding to the intraocular pressure reading 20 and in either case, standard medical testing can be performed with the device of the present invention to measure the relevant intraocular pressure, i.e. the pressure at which the pressure is perceived as flashing, with the actual pressure in the eye. This approval was performed by a Goldmann applanation tonometer in both the relevant and standard tests. This correlation allows for variations in tissue stiffness of the eyelids and sclera and can be compensated for.

It has been found that normal intraocular pressure can vary among different groups of people. Thus the normal value for some people may be a low reading. The problematic intraocular pressure can be seen as a simple mean pressure for this purpose.

To accommodate this, the pressure scale actually needs to be varied for different types of users. This can be done in a number of ways. Where the scale on the device itself is associated with a watch, it is a simple matter to provide a different watch adapted to different users. If a given pressure reading is on the scale, different springs of different spring rates can be used, effectively changing the different readings on the scale of applied pressure. Another solution is to change the diameter of the head in contact with the eyelid, which can be used in combination with different springs. Typically for comparison purposes, the head 32 has the same size and configuration as a Goldmann tonometer. The patient will then be tested to determine which type or group he belongs to before handing the device to the patient or user, and once determined, will provide a suitable device that can be used for home testing.

If the measured pressure is outside the desired limits, the user will be instructed to take the treatment provided to him beforehand and/or to visit a suitable medical specialist, providing further examination conditions. For example, if the user has a known intraocular pressure that is too high, which is within a certain intraocular pressure range, the user simply has to be instructed to take the previously dispensed medication. However, if the eye pressure is higher than the perceived set pressure, the user will be instructed to see his or her doctor.

As mentioned above, for the next use, for example on the other eye, the return member 44 is simply grasped to depress the flag member 24 to cause it to move to the null position. The two ends of the marking member representing zero are purely arbitrary and may be illustrated with structural material on the device.

The tonometer of the present invention has the advantage of being simple and durable and can be produced at a very low cost. Its great advantage is that it can be used by ordinary people or patients without the need for sophisticated trained medical personnel. More importantly, it can be used in any situation and need not be used in a medical office, hospital or the like.

Reference is now made to fig. 2-6, which illustrate a second preferred embodiment of the present invention. This second embodiment corresponds in principle to the first, however a single part is suitable for simple moulding from plastic. Tonometer 60 herein has a body or cover 62, 62. A plunger 64 is mounted at one end of the body 62 and a return member 66 having an integral marking member is mounted at the other end as will be described in more detail below. Each of these parts will be described in turn below.

The body 62 has a tubular middle portion 68 which defines a central bore and includes a slot 70 with a scale 72 on one side of the slot.

The first end of the body includes a rounded end portion 74 having a smaller diameter than the central portion of the body such that it defines an annular rim or flange 75. Extending axially inwardly from the end 74 are a pair of ribs 76, as best seen in fig. 4 and 5, the innermost portions of the ribs 76 forming a cross-member 78 that extends radially across the body 62.

At a second end of the body 62, there is a recess 80 surrounded by a baffle 82.

The plunger 64 is generally tubular and has a bore 88 and a flat end face 90 which is connected to the tubular side wall of the plunger 64 by a rounded or tapered portion, with an annular projection 96 extending around the free end of the leg 92 for engagement with the annular rim 75 of the body.

Within bore 88 is a coil spring 98 for biasing plunger 64 to its extended position. To assemble the plunger 64 in place. Spring 98 is inserted into plunger bore 88 and the plunger is then passed through end 74. The annular projection 96 has a tapered or inclined end face for pressing together the legs 92 so that they pass through the bore of the rounded end portion 74. When fully inserted, the spring of leg 92 is outward, causing annular projection 96 to engage annular rim 75, securing the plunger in place.

Return member 66 includes a head 100, a pair of side legs 102 and a slide member 104 adapted to slide freely within the bore of body 62.

The slide member 104 includes a circular disc and a pair of short tabs 106 for abutting the end of the plunger 64 in the zero position, as shown in fig. 5, with the cross beam 78 located between the tabs 106.

Each leg 102 includes a first leg portion 108, a friction portion 110, and a second leg portion 112. The second leg 112 is smaller than the first leg 108 and is primarily used to attach the head 100 to the seat of the return member 66. The first leg 108 has a larger dimension and is formed with a friction portion 110 that is biased radially outward. Friction portion 110 is then pressed into tubular mid-portion 68, as shown in fig. 5, thereby frictionally retaining return member 66 in position. The amount of friction is such that return member 66 does not move during normal handling of tonometer 60, while at the same time the magnitude of friction is not so high as to greatly affect the force required to move return member 66.

The second leg 112 is of a smaller size and essentially serves as a connection for the head 100 to the return member 66.

The illustrated head 100 has a semi-circular edge 114 on one side and a square edge portion 116 on the other side, which correspond to the recess 80.

Extending from the head 100 is an arm 118 at the free end of which is an indexing projection 120 having an indexing arrow 122. The nose 120 has a front end with an inclined surface 124 and a rear face 126 perpendicular to the axis of the device for reasons which will be described below.

To insert the return member into position it is simply slid along the axis of the body 62. The inclined surface 124 engages the stop plate 82 and deflects the nose 120 radially inwardly. The arm 118 causes the projection 120 to eject outwardly of the slot 70. In this position, the face 126 will prevent the return member from accidentally disengaging.

The second embodiment is used in substantially the same manner as the first embodiment. The spring holds the plunger 64 in a normally extended position, which is compressed between the cross beam 78 and the end of the plunger 64. Before using the device, the user simply grasps the body with one hand and depresses the head 100 with a finger to move the return member 66 to or ensure that it is in the rest position in which the marking nose 120 is located near the zero position of the scale 72. This stop position is shown in fig. 3, and it can be seen that the notch 80 provides suitable finger access.

The tonometer is then pressed onto the eye as in the first embodiment and pressed with a finger on head 100, moving return member 66 and plunger 64 until pressure is felt by the eyelash flash. The tonometer is then removed and the position of the marker member 104 indicated by the position of arrow 122 on the scale 72 is recorded, which is the load or force at which the pressure tamponade flash occurs, i.e. the intraocular pressure.

Having described preferred embodiments of the invention, it will be apparent that various modifications may be made within the scope of the invention. For example: in the first embodiment, return member 44 has been described as being separate from flag member 24, and it may be mounted on the return member to eliminate spring 49. This can be done by: the marker member 24 is formed as a disc of resilient material having a central aperture which is mounted at one end of the return member 44 and retained thereon by a tab.

For both embodiments, it is preferred that the body, plunger and return member are all moulded from plastics. At least the scale portion of the body is transparent or at least the marking member is visible so that movement of the marking member on the scale is visible through the body. Typically the entire body is made of clear plastic, a material such as that used for syringes and the like, or has a groove.

Either of the body 12 and the plunger 26 may carry a marking member and either may carry no elements of the marking member to provide a scale.

Claims (16)

1. An applanation tonometer for measuring intraocular pressure in a human eye, the tonometer comprising: a body, generally tubular, defining an aperture and including a graduated portion; a plunger slidably mounted in the bore of the body, extending outwardly from a first end of the body and including a head on one end thereof for contact with the eyelid, the plunger being retained at its other end within the body, the head being sufficiently large that, in use, the eyeball is flattened and a flattened cornea is produced; spring biasing means acting between the plunger and the body to bias the head away from the body; and a marking member frictionally held within the bore of the body for movement relative to the scale by the plunger to indicate a maximum load applied to the plunger, wherein the graduated portion of the body includes viewing means to allow the position of the marking member relative to the scale to be externally visible.

2. A tonometer as claimed in claim 1, wherein the first end of the body adjacent the plunger includes a first radially inwardly extending flange means and the plunger includes a first radially outwardly extending projection means at said other end thereof, the first flange means and the first projection means being dimensioned to retain the other end of the plunger within the body.

3. A tonometer as claimed in claim 2, wherein the first projection means comprises an annular projection having a generally conical surface which reduces in diameter away from said one end of the plunger, and a flat surface; the tapered surface is for moving the first retaining flange means radially outwardly to allow insertion of the plunger during assembly of the tonometer, and the flat surface is dimensioned to abut the first retaining flange means to retain said one end of the plunger within the body.

4. A tonometer as claimed in claim 3, wherein the spring biasing means comprises a coil spring mounted between the flange of the main body and the head against the eyelid.

5. A tonometer as claimed in any preceding claim, wherein the body is generally elongate and is moulded from a transparent material.

6. A tonometer as claimed in any one of claims 1 to 4, including a return member slidably mounted in the bore and extending from the second end of the body, the return member enabling the user to move the marker member.

7. A tonometer as claimed in claim 6, wherein the second end of the body includes second radially extending flange means, and the return member includes an end located within the body which includes second radially outwardly extending annular projection means, the second flange means and the second annular projection means being adapted to retain the return means within the body.

8. A tonometer as claimed in claim 7, wherein the marker member is secured to the return member so as to move therewith.

9. A tonometer as claimed in claim 6, wherein the marker member is integral with the return member, the return member including means for retaining the return member within the main body.

10. A tonometer as claimed in claim 9, wherein: the body includes an elongated slot along which the scale is disposed, and the flag member includes a flag projection secured to the return member and located within the slot, the flag projection including an end surface abutting an end of the slot which prevents the flag member from being removed.

11. A tonometer as claimed in claim 10, wherein the marker projection is mounted on the end of the resilient arm and includes an inclined face to enable radially inward movement of the marker projection to facilitate insertion of the return member and marker member into the body.

12. A tonometer as claimed in claim 9, wherein the return member comprises a slide member adapted to slide freely within the bore of the body, a head at the other end of the return member being manually moved by the user, and leg means connecting the head to the slide member, the leg means comprising friction means resiliently urged against the body to frictionally hold the return member in position.

13. A tonometer as claimed in claim 12, wherein the leg means comprises a pair of oppositely located legs, each leg comprising a first leg portion extending from the slide member, a second leg portion extending from the head and a friction portion between the first and second leg portions.

14. A tonometer as claimed in claim 13, wherein the first leg is larger than the second leg.

15. A tonometer as claimed in any of claims 9 to 14, wherein the main body includes a recess at its second end and a baffle means dimensioned such that for all positions of the marker member displaced along the scale, the head of the return member is located within the recess, the recess being sufficiently large to enable the head of the return member to be displaced along the recess to return the return member to a zero position on the scale.

16. A tonometer as claimed in claim 15, wherein the baffle projects outwardly from the main body, and wherein the head portion comprises a semi-circular portion and a rectangular portion, the latter being located within the recess.