Flexible headrests for ophthalmic instruments

Abstract

A headrest for ophthalmic instruments facilitates precise positioning of the instrument relative to the test subject's eye without requiring the removal of the headrest's contact elements from contact with the test subject's face. The ophthalmic instrument may be, for example, a spring-loaded tonometer or a non-contact tonometer. The headrest includes a hollow spherical contact element formed from an elastically deformable material, such as thermoplastic elastomer (TPE) or silicone rubber. When the contact element is not deformed, its outer surface can have a spherical or near-spherical shape.

Description

Technical Field

[0001] This invention relates to ophthalmic instruments in which the operator positions the instrument relative to the eye of the test subject as a prerequisite for measuring ophthalmic parameters of the eye. For example, this invention relates to a spring-loaded tonometer that measures intraocular pressure (IOP) by contacting the cornea with a disposable probe, and a non-contact tonometer that measures IOP by temporarily deforming the cornea using an air pulse. Background Technology

[0002] A spring-loaded tonometer is an ophthalmic instrument that measures intraocular pressure (IOP) by advancing a movable measuring probe along a measuring axis toward the cornea in a controlled manner. During measurement, the probe contacts the cornea, decelerates at a rate based on the IOP, and springs back toward the instrument housing in a direction away from the cornea. The spring-loaded tonometer detects the probe's motion and determines the IOP based on the detected probe motion. For example, the measuring probe may have a magnetized axis traveling within a coil in the instrument housing. The coil can be momentarily energized to push the probe toward the cornea by electromagnetic force, and then, after the energizing current to the coil is cut off, a current can be induced in the coil by the moving probe to provide a detectable voltage signal representing the probe velocity over time. Alternatively, two coils can be provided, one for advancing the probe and the other for inducing a current in the moving probe to provide a measuring voltage signal. The voltage signal can be recorded and processed to determine the measured IOP value.

[0003] Accurate three-dimensional positioning of the rebound tonometer relative to the eye is crucial for the accuracy and repeatability of IOP measurements.

[0004] Non-contact tonometers, also known as jet tonometers, are another type of ophthalmic instrument used to measure intraocular pressure (IOP). Like spring tonometers, non-contact tonometers can be held and manually positioned by the operator. Except for the fluid discharge tube used to deliver pulses of air to the eye, which defines the measurement axis and working distance, non-contact tonometers have similar three-dimensional positioning requirements to the aforementioned spring tonometers.

[0005] The ophthalmic instruments described above include a measuring head that carries the measuring hardware, and the measuring axis of the instrument extends from the measuring head. In the case of handheld instruments that are manually positioned relative to the test object, a handle extending downwards from the measuring head is typically provided. Although perfect or ideal three-dimensional positioning is impossible due to movement of the test object and / or movement of the operator's hand while holding the instrument, three-dimensional positioning within acceptable tolerances relative to an ideal position is a prerequisite for obtaining reliable measurement results.

[0006] To assist the operator in positioning the instrument relative to the test object, a headrest is known to extend forward beyond the front of the measuring head at a position vertically spaced from the measuring axis. The headrest includes a contact element at its front end for contacting the test object's face. When the headrest is above the measuring axis, the contact element contacts the test object's forehead; when the headrest is below the measuring axis, the contact element contacts the test object's cheek. In a known arrangement, the contact element is mounted at the front end of a threaded adjustment mandrel extending parallel to the measuring axis. A knob is mounted at the rear end of the mandrel, which fits into a threaded sleeve fixed to the instrument. Thus, the extension distance of the contact element beyond the front of the instrument can be adjusted (i.e., extended and retracted) by rotating the knob.

[0007] The headrests described above are helpful, but they have drawbacks. If the extension distance of the headrest's contact element is set too large, the instrument cannot be properly positioned because it is too far from the test subject's eyes, and the measurement will result in erroneous information, such as "too far." Conversely, if the extension distance of the headrest's contact element is set too small, the instrument cannot be properly positioned because it is too close to the test subject's eyes, and the measurement will result in erroneous information, such as "too close." Therefore, the operator must adjust the headrest and repeat the measurement until the instrument is correctly positioned. Even if the extension distance is set appropriately, if the contact element is placed too far to the left or right, or too high or too low on the forehead or cheek, the operator must remove the instrument from the test subject's face before repositioning the contact element to achieve proper alignment. In summary, when the headrest's contact element remains in contact with the test subject's face, existing headrests are not convenient for fine-tuning the instrument's positioning in the X, Y, and / or Z directions. Summary of the Invention

[0008] This disclosure provides a headrest for an ophthalmic instrument that facilitates precise positioning of the instrument relative to the eye of a test subject without requiring the removal of the headrest's contact unit to prevent it from contacting the test subject's face. For example, the ophthalmic instrument could be a spring-loaded tonometer that advances a probe toward the eye along the instrument's measurement axis, or a non-contact tonometer that discharges fluid pulses toward the eye along the instrument's measurement axis.

[0009] In one embodiment of this disclosure, an ophthalmic instrument for measuring ophthalmic parameters of a test subject's eye typically includes a measuring axis and a headrest vertically spaced from the measuring axis, wherein the headrest includes a hollow spherical contact element made of an elastically deformable material, such as a thermoplastic elastomer (TPE) or silicone rubber. When the contact element is not deformed, the outer surface of the contact element may have a spherical or near-spherical shape.

[0010] In embodiments of this disclosure, the headrest may include a base and a retainer, and the contact element may have a circumferential mounting portion that receives and is held between the base and the retainer. The retainer may be attached to the base by engaging with a snap-fit ​​mechanism with the base.

[0011] When the operator makes precise positioning adjustments to the instrument relative to the eyes in three spatial dimensions X, Y, and z, the hollow spherical contact element can maintain contact with the patient's face and undergo reversible deformation. Attached Figure Description

[0012] The nature and operating mode of the present invention will be described more fully in the following detailed description in conjunction with the accompanying drawings, wherein:

[0013] Figure 1 This is a perspective view of an ophthalmic instrument with a flexible headrest according to an embodiment of the present invention, wherein an operator is positioning the ophthalmic instrument relative to the eye of a test subject to perform a measurement;

[0014] Figure 2 This is an exploded perspective view showing the contact elements of the flexible headrest and the structure for mounting the contact elements on the adjustment mandrel of the headrest;

[0015] Figure 3 yes Figure 2 The cross-sectional view of the contact element and mounting structure is shown.

[0016] Figure 4A and 4B This is a perspective view showing the flexible compliance of the contact elements of the headrest when the working distance of the ophthalmic instrument is adjusted relative to the eye of the test subject; and

[0017] Figure 5 This is a perspective view showing the flexible compliance of the contact elements of the headrest when the ophthalmic instrument is positioned laterally and vertically relative to the eye of the test subject. Detailed Implementation

[0018] Figure 1An ophthalmic instrument 10 for measuring ophthalmic parameters of the eye according to an embodiment of the present invention is shown. In the figure, the ophthalmic instrument 10 is implemented as a rebound tonometer for measuring the intraocular pressure (IOP) of a test subject TS; however, it should be understood that the ophthalmic instrument 10 can be implemented as a non-contact tonometer for measuring IOP, or as another type of ophthalmic instrument for measuring eye parameters other than IOP. The ophthalmic instrument 10 includes a measuring axis 11. In the case of the rebound tonometer shown, the measuring axis 11 is the axis along which a measuring probe (not shown) is pushed toward the eye of the test subject. In the case of the non-contact tonometer, the measuring axis 11 is the axis of a fluid outlet tube through which a fluid pulse (e.g., an air jet) is directed toward the eye of the test subject TS.

[0019] The ophthalmic instrument 10 may include a handle 12 and a measuring head 14 atop the handle 12. A measurement button (not shown) may be provided on the handle 12 for initiating the measurement. The ophthalmic instrument 10 may also include a display 15 for presenting information to the operator, and menu navigation / selection buttons 16 that allow the operator to input information. For example, the display 15 may be used to show the operator a real-time positioning guidance image to help guide the operator in positioning the ophthalmic instrument 10 relative to the eye of the test subject for measurement. The display 15 may also be used to display control menus, measurement results, test subject data, and other information to the operator.

[0020] The ophthalmic instrument 10 also includes a headrest 20 supported by a measuring head 14. The headrest 20 may include an adjustment knob 22 mounted at the rear end of the adjustment spindle 23 and a contact element 24 mounted at the front end of the adjustment spindle 23.

[0021] Figure 2 and Figure 3 The contact element 24 and the structure for mounting the contact element on the adjusting mandrel 23 are shown in more detail. As can be seen, the contact element 24 is a hollow spherical element. The contact element 24 is formed of an elastically deformable material. For example, the contact element 24 can be formed of a thermoplastic elastomer (TPE), such as Versaflex OM 1040X-9 hardness tester 40A. Other brands, grades, and types of TPE can be used to form the contact element 24. Of course, elastically deformable materials other than TPE, such as silicone rubber, can be used to form the contact element 24. Because the contact element 24 comes into contact with the skin of the test subject, it is beneficial to form the contact element 24 from a biocompatible, hypoallergenic, easy-to-clean, and disinfectable material.

[0022] As from Figure 2 and Figure 3As can be seen, when the contact element 14 is not deformed, the outer surface 25 of the contact element 24 can have a spherical or near-spherical shape. The size of the contact element 24 can be configured to provide a comfortable and stable face-to-face contact area with the forehead FH of the test subject TS when the instrument 10 moves close to the eye, such that the contact portion of the outer surface 25 conforms to the forehead of the test subject. As a non-limiting example, the outer surface 25 of the contact element 24 can be shaped as a sphere to have a radius of curvature ranging from 9 mm to 11 mm on the front portion of the contact element 24. In one embodiment, the radius of curvature is approximately 10 mm.

[0023] The headrest 20 also includes a structure for mounting the contact element 24 to the end of the adjusting spindle 23. For example, the headrest may include a base 30, a retainer 40, and a threaded fastener 50 for mounting the contact element 24 to the adjusting spindle 23. The contact element 24 may have a circumferential mounting portion 26 that receives and holds between the base 30 and the retainer 40. In the illustrated embodiment, the mounting portion 26 of the contact element 24 includes a cylindrical edge 27 and a flange 28 extending radially from the cylindrical edge 27, wherein both the cylindrical edge 27 and the flange 28 are held between the base 30 and the retainer 40. The base 30 and the retainer 40 may be integrally molded plastic parts. The retainer 40 can be attached to the base 30 by engaging with a snap-fit ​​connection to the base 30. For example, the base 30 may include a plurality of resiliently deflectable gripping arms 36, which are angularly spaced about the central axis of the base 30 and configured to deflect through a central opening 42 in the retainer 40 when the base 30 and the retainer 40 become coaxial, until the corresponding barb ends of the gripping arms engage with corresponding protrusions 44 of the retainer 40, thereby preventing the retainer 40 from retracting. Figure 3 As can be understood, during the assembly of the base and the retainer, the circumferential mounting portion 26 of the contact element 24 is securely clamped between the base 30 and the retainer 40.

[0024] The threaded fastener 50 can be attached to the rear of the base 30, thereby allowing the entire assembly, including the contact element 24, to be mounted on the front end of the adjusting spindle 23 by fitting the fastener 50 into a threaded hole (not shown) at the front end of the adjusting spindle. The threaded fastener 50 can be attached to the base 30 in any suitable manner. For example, in the embodiment shown in the figures, the base 30 has a central hub 32 including a recess 34, and the threaded fastener 50 includes a head 52 that receives and is held in the recess 34 of the central hub 32. The head 52 can be press-fitted into the recess 34 and / or secured in the recess by an adhesive.

[0025] Figure 4A , Figure 4B and Figure 5The ophthalmic parameters of the eye of the test subject TS are shown to be measured using an ophthalmic instrument 10 with a headrest 20. Figure 4A and 4B The flexible compliance of the contact element 24 with the forehead FH is shown when the working distance of the ophthalmic instrument 10 is adjusted relative to the eye of the test subject TS. Figure 4A In the middle, the ophthalmic instrument 10 is in contact with the forehead FH. Figure 4B In the process, when the ophthalmic instrument 10 moves the forehead FH to reduce the Z-axis working distance, the contact element 24 is reversibly compressed to accommodate fine position adjustments.

[0026] Figure 5 The flexibility of the contact element 24 is shown when the ophthalmic instrument 10 is positioned laterally and vertically relative to the eye of the test subject TS. Figure 5 In a representative view, the ophthalmic instrument 10 moves slightly downward (Y-axis) and to the left (X-axis), and the contact element 24 reversibly deforms to accommodate fine position adjustments while maintaining contact with the forehead FH.

[0027] Although the embodiment of the ophthalmic instrument 10 shown in the accompanying drawings illustrates a headrest 20 positioned above the measurement axis 11 to contact the forehead FH of the test subject TS, those skilled in the art will recognize that the headrest 20 may be positioned below the measurement axis 11 to contact the cheek of the test subject TS.

[0028] This disclosure provides a headrest for ophthalmic instruments that facilitates precise positioning of the instrument relative to the test subject's eyes and provides comfort to the test subject. The headrest of this disclosure significantly reduces the need to remove the contact elements of the headrest from contact with the test subject's face to reposition the contact elements on the face and / or adjust the extension / retraction position of the contact elements relative to the measuring head of the instrument. Therefore, both measurement efficiency and the test subject's experience are improved.

[0029] While this disclosure describes exemplary embodiments, the detailed description is not intended to limit the scope of the appended claims to the particular embodiments described. The claims are intended to cover alternatives, modifications, and equivalents to the embodiments described, all of which may be included within the scope of the claims.

Claims

1. An ophthalmic instrument (10) for measuring an ophthalmic parameter of an eye of a test subject, the ophthalmic instrument (10) comprising: a measurement axis (11); and a headrest (20) vertically spaced from the measurement axis (11), wherein the headrest (20) comprises a hollow spherical contact element (24) formed of a resiliently deformable material; wherein the headrest (20) comprises a base (30) and a retainer (40), the contact element (24) having a circumferential mounting portion (26), wherein the mounting portion (26) of the contact element (24) is received between the base (30) and the retainer (40); wherein the mounting portion (26) of the contact element (24) comprises a cylindrical rim (27) and a flange (28) extending radially from the cylindrical rim (27), wherein the cylindrical rim (27) and the flange (28) are both retained between the base (30) and the retainer (40).

2. The ophthalmic instrument (10) of claim 1, wherein an outer surface (25) of the contact element (24) has a spherical or spheroid shape when the contact element (24) is not deformed.

3. The ophthalmic instrument (10) of claim 2, wherein the outer surface (25) of the contact element (24) has a spherical shape with a radius of curvature in a range of 9 millimeters to 11 millimeters.

4. The ophthalmic instrument (10) of claim 3, wherein the radius of curvature is about 10 millimeters.

5. The ophthalmic instrument (10) of claim 1, wherein the resiliently deformable material is a thermoplastic elastomer (TPE) or a silicone rubber.

6. The ophthalmic instrument (10) of claim 1, wherein the retainer (40) is attached to the base (30) by a snap-fit engagement with the base (30).

7. The ophthalmic instrument (10) of claim 1, wherein the base (30) has a central hub (32) including a recess (34), the headrest further comprising a threaded fastener (50) having a head (52) received in the recess (34) of the central hub (32).

8. The ophthalmic instrument (10) of claim 7, wherein the head (52) of the threaded fastener (50) is press-fit into the recess (34) of the central hub (32). ​

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