JP6661924B2 - Non-contact tonometer - Google Patents

Description

  The present disclosure relates to a non-contact tonometer for measuring an intraocular pressure of a subject's eye in a non-contact manner.

  A non-contact tonometer that injects a fluid such as air toward a subject's eye through a nozzle, detects a predetermined deformed form of the cornea (for example, an applanation state) due to the ejected fluid, and measures the intraocular pressure has been developed. Are known. In such an apparatus, a driving current is supplied to a driving unit such as a solenoid, and the piston in the cylinder is pushed forward by the driving force, whereby a fluid is sprayed on the cornea of the eye to be examined to deform it. Further, after the fluid is ejected to the eye to be examined, the piston is returned to the initial position in preparation for the next measurement of the intraocular pressure.

JP-A-03-118034 JP-A-2004-89455

  However, for example, in the conventional devices as shown in Patent Documents 1 and 2, the piston is returned to its initial position by its own weight or a return force such as a spring. In such a case, it has been difficult to appropriately control the force applied to the piston.

  The present disclosure has been made in view of the conventional problems, and has as its technical object to provide a non-contact tonometer capable of suitably controlling a force applied to a piston.

  In order to solve the above problem, the present disclosure is characterized by including the following configuration.

(1) A non-contact tonometer for measuring an intraocular pressure of an eye to be examined in a non-contact manner, wherein a driving means for generating a driving force by supplying a driving current, and a piston in a cylinder driven by the driving means. A fluid ejection unit for ejecting a fluid to the cornea of the eye by moving in a first direction to perform a pressurizing operation; and a control unit for controlling supply of a drive current to the drive unit; Supplies a first driving force in the first direction to the piston by supplying a driving current in a forward direction to the driving means, and supplies a driving current in a direction opposite to the forward direction to the driving means. A second driving force in a second direction opposite to the first direction is applied to the piston, and the fluid ejection unit horizontally moves the piston by the driving unit in the cylinder arranged in parallel with a horizontal plane. Moved to Characterized that you inject fluid into the cornea of the eye by by moving to the pressing operation.

FIG. 3 is a diagram illustrating a schematic side view of a fluid ejecting unit that ejects a fluid (for example, air) to the cornea of a subject and a specific example of a control system in the non-contact tonometer according to the embodiment. FIG. 4 is a view showing a specific example of an optical system for detecting a deformed state of the cornea due to a fluid ejection unit, and is a view of an optical system near a nozzle as viewed from above. It is a figure which shows the current waveform to a solenoid and the pressure waveform of a nozzle part at the time of using the restoring force of a spring as a restoring force, and the case of using the driving force of a solenoid as a restoring force. It is a figure which compares the pressure waveform of a nozzle part at the time of using the restoring force of a spring as a restoring force, and the case of using the driving force of a solenoid as a restoring force.

  Hereinafter, the non-contact tonometer of the present embodiment will be briefly described. The non-contact tonometer of the present embodiment measures, for example, the intraocular pressure of the eye to be examined in a non-contact manner. For example, the non-contact tonometer may eject the fluid to deform the cornea of the eye E, and measure the intraocular pressure of the eye E based on the deformed state and the pressure of the fluid. The non-contact tonometer includes, for example, a driving unit (for example, the solenoid 3), a fluid ejection unit (for example, the fluid ejection unit 30), and a control unit (for example, the control unit 70).

  The driving unit generates a driving force by supplying a driving current, for example. The fluid ejection unit ejects a fluid to the cornea of the eye by, for example, moving a piston in a first direction in a cylinder by a driving unit to perform a pressurizing operation. The first direction is, for example, a direction in which the piston moves when compressing air in the cylinder. The control unit controls supply of a drive current to the drive unit, for example. Of course, the control unit may control the supply of the drive current to the drive unit by controlling the drive voltage. The control unit may apply a first driving force in the first direction to the piston by supplying a forward driving current to the driving unit, for example. Further, the control unit may apply a second driving force in a second direction opposite to the first direction to the piston by supplying a driving current in a direction opposite to the forward direction to the driving unit, for example. Note that the direction of the drive current may be switched using various switch circuits such as an H-bridge circuit.

  The control unit may reduce the moving speed of the piston by applying a second driving force to the piston moving in the first direction by the first driving force, for example.

  Note that the control unit may control the drive current supplied to the drive unit to apply a second drive force greater than the first drive force to the piston moving in the first direction by the first drive force. Good. Thereby, for example, the piston may be quickly decelerated.

  Note that the control unit may adjust the magnitude of the second driving force applied to the piston by controlling the reverse driving current supplied to the driving unit. For example, the control unit may increase the driving force of the driving unit by increasing the driving current.

  Note that the control unit may adjust the time for applying the second driving force to the piston by controlling the supply time for supplying the driving current in the reverse direction to the driving unit. For example, the control unit may supply the driving current for a long time to lengthen the time of the second driving force applied to the piston.

  The control unit controls at least one of the magnitude and the supply time of the reverse drive current supplied to the drive unit according to at least one of the magnitude and the supply time of the forward drive current supplied to the drive unit. By controlling, the magnitude of the second driving force may be adjusted according to the magnitude of the first driving force. For example, when increasing the first driving force, the control unit may increase the magnitude of the second driving force accordingly.

  The present device may further include, for example, a deformation detection unit (for example, the detection optical system 10). The deformation detecting unit detects, for example, the deformation of the cornea by the fluid ejecting unit. In this case, the control unit may detect the rising of the detection signal output from the deformation detection unit. Then, the control unit may supply a driving current in the opposite direction to the driving unit and apply the second driving force to the piston so as to stop the pressurizing operation due to the movement of the piston in the first direction. The control unit may detect the rising of the detection signal when the deformation detection unit detects the deformation of the cornea for a predetermined time.

  The control unit moves the piston in the first direction from the initial position to the pressurizing end position by the first driving force, and moves the piston in the second direction from the pressurizing end position to the initial position by the second driving force, for example. May be.

  Note that the present device may further include a position detection unit (for example, the position detection sensor 50). The position detector detects, for example, the position of the piston. In this case, the control unit may change the drive current supplied to the drive unit according to the position of the piston detected by the position detection unit.

  Note that, after the pressurizing operation of the piston, the control unit may temporarily stop the piston and then return the piston to the initial position. When temporarily stopping the piston, the control unit may stop supplying the drive current.

  The fluid ejection unit may eject the fluid to the cornea of the subject's eye by performing a pressurizing operation by moving the piston horizontally by a driving unit in a cylinder arranged in parallel with a horizontal plane. That is, the cylinder and the piston may be arranged horizontally. In this case, similarly to the above, the control unit may stop supplying the drive current when temporarily stopping the piston. This causes, for example, blisters in which no driving force acts on the piston, and the piston stops.

  Note that the drive unit may be a direct acting solenoid. The direct acting solenoid has, for example, a linear operation direction.

<Example>
Hereinafter, this embodiment will be described with reference to the drawings. The non-contact tonometer of the present embodiment measures, for example, the intraocular pressure of the eye to be examined in a non-contact manner. The non-contact tonometer, for example, ejects a fluid to the cornea of the eye to be inspected, and measures the intraocular pressure of the eye to be inspected from the relationship between the deformation state of the cornea and the pressure of the fluid at that time. As shown in FIG. 1 or FIG. 2, the non-contact tonometer includes, for example, a fluid ejection unit 30, a detection optical system 10 (FIG. 2), an observation / alignment optical system 11, a control unit 70, and the like. The fluid ejection unit 30 ejects a fluid to the cornea of the eye E, for example. The detection optical system 10 detects, for example, a deformed state of the cornea of the eye E to be inspected. The observation / alignment optical system 11 captures an observation image of the eye to be inspected, projects an alignment index, and the like. The control unit 70 controls, for example, the entire apparatus. Note that the X direction in FIG. 1 represents the left-right direction, the Y direction represents the up-down direction, and the Z direction represents the front-back direction.

<Fluid ejection section>
The fluid ejection unit 30 includes, for example, a cylinder 1, a piston 2, a solenoid actuator (hereinafter, also referred to as a solenoid) 3, and a nozzle 6. The cylinder 1 and the piston 2 are used as an air compression mechanism that compresses air that is ejected to the eye. The cylinder 1 is, for example, cylindrical. The piston 2 slides along the axial direction of the cylinder 1. The piston 2 compresses air in the air compression chamber 34 in the cylinder 1. The solenoid 3 according to the present embodiment is a so-called direct acting solenoid, and operates linearly. The solenoid 3 includes a movable body 4 and a coil 5. As the movable body 4, for example, a magnetic body such as a permanent magnet is used. When a current flows through the coil 5, a magnetic field is generated inside the coil 5. The movable body 4 is moved in the direction A in FIG. 1 by the electromagnetic force received from the magnetic field. The movable body 4 is fixed to the piston 2 by screws, bolts, nuts and the like (not shown). Therefore, the piston 2 moves together with the movable body 4. The movement of the movable body 4 moves the piston 2 in the compression direction (or the forward direction, the direction A in FIG. 1).

  The air compressed in the air compression chamber 34 in the cylinder 1 by the movement of the piston 2 passes through a tube (may be a pipe) 20 connected to the tip of the cylinder 1 and an airtight chamber 21 containing the compressed air. It is ejected from the nozzle 6 toward the cornea of the subject's eye E. Note that, for example, the cylinder 1 is arranged parallel to a horizontal plane (XZ plane), and air may be compressed by driving the solenoid 3 to move the piston 2 horizontally in the cylinder 1. . For example, the cylinder 1 is arranged so that its longitudinal direction is parallel to the horizontal direction, and the inner surface of the cylinder 1 guides the piston 2. Therefore, the moving direction (compression direction) of the piston 2 is horizontal. Each of the above components is arranged on a stage provided in the housing of the apparatus main body (not shown).

  Further, the solenoid 3 of the present embodiment can change the moving direction of the movable body 4 by changing the direction of the current flowing through the coil 5. For example, the movable body 4 moves in the compression direction (forward direction, direction A in FIG. 1) when a current flows through the coil 5 in the forward direction, and moves in the opposite direction (retreat direction) when the current flows in the reverse direction. , B direction in FIG. 1). Therefore, the direction of movement of the piston 2 that moves together with the movable body 4 can be changed by switching the direction of the current flowing through the coil 5. For example, a forward current is applied to the coil 5 to move the piston 2 in the A direction to compress the air in the air compression chamber 34, and then a reverse current is applied to the coil 5 to move the piston 2 in the B direction. It can be moved back to its initial position.

  The fluid ejection unit 30 may include, for example, a glass plate 8 and a glass plate 9. The glass plate 8 is transparent, holds the nozzle 6, and transmits observation light and alignment light. The glass plate 9 forms a rear wall of the airtight chamber 21 and transmits observation light and alignment light. Behind the glass plate 9, the observation / alignment optical system 11 is disposed so that the observation optical axis and the alignment optical axis are coaxial with the axis of the nozzle 6, but since this is less relevant to the present disclosure, Description is omitted.

  The fluid ejection unit 30 may include, for example, the pressure sensor 12 and the air vent hole 13. The pressure sensor 12 detects, for example, the pressure in the airtight chamber 21. In the air vent hole 13, for example, the resistance until the piston 2 reaches the initial speed is reduced, and a time-proportional rising pressure change can be obtained.

<Detection optical system>
The detection optical system 10 includes a light source 14, a collimator lens 15, a light receiving lens 16, a pinhole plate 17, a light receiving element 18, and the like. The light source 14 may be, for example, an infrared LED for detecting corneal deformation. The collimator lens 15 emits the light emitted from the light source 14 to the cornea of the eye E as a parallel light flux. The light receiving lens 16 and the pin pole plate 17 allow the light reflected by the cornea to pass through and be received by the light receiving element 18. The detection optical system 10 is arranged so that the amount of light received by the light receiving element 18 is maximized when the subject's eye is in a predetermined applanation state.

<Control system>
The non-contact tonometer includes, for example, a control unit 70. The control unit 70 controls, for example, the entire apparatus. The control unit 70 is connected to, for example, the solenoid 3, the detection optical system 10, the observation / alignment optical system 11, the pressure sensor 12, the position detection sensor 50, and the like. The control unit 70 may perform, for example, signal processing from the pressure sensor 12, signal processing from the light receiving element 18, drive control of the solenoid 3, and the like.

<Control operation>
The control operation of the non-contact tonometer having the above configuration will be described. The examiner arranges the eye E at a predetermined position and operates a joystick (not shown) to adjust the alignment. When the alignment is completed, the examiner presses the measurement start switch (or the control unit automatically issues a measurement start signal based on a signal from the alignment optical system) to start the measurement.

  When the measurement start signal is input, the control unit 70 starts applying a current as operable driving energy to the solenoid 3. When the solenoid 3 operates and its driving force is transmitted to the piston 2, the piston 2 advances in the compression direction, and the air compressed in the cylinder 1 compresses the air in the airtight chamber 21 through the tube 20. I do. Then, the compressed cornea of the eye to be inspected is blown through the nozzle 6 to gradually deform the cornea of the eye to be inspected.

  The reflected light of the light emitted from the light source 14 by the cornea enters the light receiving element 18, and the deformed state of the cornea is detected by the light receiving element 18. Then, when the control unit 70 detects that the amount of received light shows a predetermined peak by a signal from the light receiving element 18, it detects that the cornea of the eye to be examined has reached the applanation state. Then, the control unit 70 obtains the pressure value at the time of detecting the applanation state based on the detection signal output from the pressure sensor 12, and calculates the intraocular pressure value based on this.

  When detecting that the cornea has reached the applanation state, the control unit 70 applies a current in the opposite direction to the coil 5 and applies a driving force (return force) in the B direction to the piston 2. The piston 2 is gradually decelerated by the return force and stops. When the piston stops, the control unit 70 temporarily stops the piston 2 after a while, and then applies a restoring force to the piston 2 again to return the piston 2 to the initial position. The reason why the piston 2 is temporarily stopped after a certain time is to suppress suction of tears, dust, or the like scattered from the eye E due to ejection of the fluid. By temporarily stopping the piston 2, the timing at which the piston 2 is returned to the initial position and the timing at which tears or dust or the like scatter around the nozzle 6 can be shifted.

  When returning the piston 2 to the initial position, the control unit 70 may gradually decrease the return speed of the piston 2 in order to suppress the generation of a loud collision sound due to the piston 2 colliding with the cylinder 1. Good. For example, the current applied to the coil 5 may be changed according to the position of the piston 2. For example, the control unit 70 may detect the position of the piston 2 with the position detection sensor 50 and supply a current set according to the position to the coil 5. For example, the control unit 70 may reduce the current flowing through the coil 5 as the piston 2 approaches the initial position. Thereby, the return force applied to the piston 2 can be reduced stepwise, and the return speed of the piston 2 can be gradually reduced. The position detection sensor 50 may be, for example, a magnetic sensor or the like. For example, the position of the movable body 4 fixed to the piston 2 may be detected by a magnetic sensor. Of course, the position detection sensor 50 may be another type of sensor (for example, an optical sensor).

  As described above, the control unit 70 of the present embodiment can switch the forward and backward movements of the piston 2 by switching the direction of the current of the coil 5. Further, by adjusting the magnitude of the current flowing through the coil 5, the magnitude of the driving force when the piston 2 is moved forward or backward can be adjusted. For example, the control unit 70 can keep the magnitude of the return force constant by keeping the magnitude of the current constant. As described above, it is easy to control the operation when the piston 2 is moved forward or backward. For example, in the case of the configuration in which the piston 2 is returned to the initial position by the restoring force of the spring or the like, the magnitude of the restoring force varies depending on the position of the piston 2 (that is, the extension of the spring), and the restoring force cannot be released. 2 is difficult to control. Further, the restoring force of the spring has a large individual difference, and it may be necessary to adjust each device. In contrast, since the fluid ejection unit 30 of the present embodiment can easily control the speed of the piston 2 by controlling the solenoid 3, it is possible to set the retreat speed of the piston 2 to be low and suppress the suction of tears or dust. it can.

  FIG. 3 illustrates a case where the piston 2 is retracted by the restoring force of the spring (see FIG. 3A) and a case where the piston 2 is retracted by switching the driving direction of the solenoid 3 (see FIG. 3B). The current waveform (solid line) supplied to the solenoid 3 by the control unit 70 and the pressure waveform (chain line) detected by the pressure sensor 12 are shown. As shown in FIG. 3A, when a spring is used, the control unit 70 applies a forward current to the solenoid 3. On the other hand, as shown in FIG. 3B, when switching the driving direction of the solenoid 3, the control unit 70 applies a forward current to the solenoid 3, and when a desired pressure is obtained, the control unit 70 reverses the solenoid 3. A current is applied in the direction to decelerate the piston 2. As shown in FIG. 4, comparing the two pressure waveforms, the pressure decreases more rapidly when the driving direction of the solenoid 3 is switched (solid line) than when a spring is used (chain line). That is, the piston 2 can be decelerated more quickly than when the restoring force of the spring is used, and it is possible to prevent unnecessary fluid from being ejected to the subject's eye. Thus, the present apparatus can reduce discomfort to the subject.

  In the present embodiment, the magnitude of the current flowing through the coil 5 when the piston 2 moving in the compression direction is stopped is smaller than the magnitude of the current flowing through the coil 5 when the piston 2 is advanced in the compression direction. Is set to be large. This is to stop the piston 2 in a short time and reduce unnecessary spraying of the fluid.

  In addition, the control unit 70 may apply a return force until the piston 2 stops by the solenoid 3, or may cancel the return force before the piston 2 stops, and the piston 3 may generate a piston force by a frictional force between the piston 2 and the cylinder 1. 2 may be stopped. Further, the control unit 70 may continue applying the restoring force until the piston 2 starts to move in the opposite direction. As described above, the control method of the solenoid 3 is not limited to the method of the present embodiment.

  The control unit 70 may detect the rise of the cornea deformation signal detected by the detection optical system 10 and switch the direction of the current to the solenoid 3 from the forward direction to the reverse direction based on the detection signal. Here, the control unit 70 switches the direction of the current to the solenoid 3 to the opposite direction, for example, when the rising is detected. At this time, the piston 2 is moved in the compression direction by the inertial force even after the current to the solenoid 3 is switched in the reverse direction, but a driving force in the direction toward the initial position is exerted by the reverse current. Then, the speed of the piston 2 is attenuated by this driving force, temporarily stopped, and thereafter moved in the return direction. In this way, by switching the direction of the current of the solenoid 3 at the timing when the cornea starts to deform before the cornea enters the applanation state, it is possible to reduce unnecessary fluid spraying to the eye to be examined, and to quickly move the piston 2. Can be returned to the initial position.

  In the above description, a non-contact tonometer is taken as an example, but a multifunction machine of a non-contact tonometer and other ophthalmic devices for measuring ocular characteristics may be used. For example, a non-contact tonometer provided with an eye-refractive-power measuring unit that measures the eye refractive power of the eye to be examined may be used.

  In the above description, a direct acting solenoid is used, but a rotary solenoid may be used. For example, the drive control of the piston 2 as described above may be performed by using a rotary solenoid capable of switching the direction of rotation by switching the direction of the current.

1 Cylinder 2 Piston 3 Solenoid 14 LED
15 Collimator lens 16 Light receiving lens 17 Pinhole plate 18 Light receiving element 20 Control unit

Claims (5)

A non-contact tonometer for measuring the intraocular pressure of the eye to be examined in a non-contact manner,
Driving means for generating a driving force by supplying a driving current;
A fluid ejecting unit that ejects a fluid to the cornea of the subject's eye by performing a pressurizing operation by moving a piston in a first direction in a cylinder by driving of the driving unit;
Control means for controlling supply of a drive current to the drive means,
The control means applies a first drive force in the first direction to the piston by supplying a forward drive current to the drive means,
A second driving force in a second direction opposite to the first direction is applied to the piston by supplying a driving current in a direction opposite to the forward direction to the driving means ,
The fluid ejection section that you inject fluid into the cornea of the eye by the pressurizing operation is moved horizontally by the driving means said piston in said cylinder which is parallel to the horizontal plane Characteristic non-contact tonometer. The non-contact tonometer according to claim 1, wherein the control means moves the piston in the second direction by the second driving force without using a restoring force of a spring . Deformation detection means for detecting the deformation of the cornea by the fluid ejection unit,
The control unit detects a rising edge of a detection signal output from the deformation detection unit, and causes the driving unit to stop the pressurizing operation by moving the piston in the first direction. The non-contact tonometer according to claim 1 or 2, wherein the second driving force is supplied to the piston. Further comprising position detection means for detecting the position of the piston,
The non-contact tonometer according to any one of claims 1 to 3, wherein the control unit changes a drive current supplied to the drive unit according to a position of the piston detected by the position detection unit. . Wherein, after the pressurizing operation end of the piston, to return to the initial position from the temporarily stopping the piston,
The non-contact tonometer according to any one of claims 1 to 4 , wherein the supply of the driving current is stopped when the piston is temporarily stopped .