Ocular axial length measurement device and ocular axial length measurement result processing program

Abstract

To provide an ocular axial length measurement device and an ocular axial length measurement result processing program capable of appropriately improving efficiency of medical care using ocular axial length measurement results.SOLUTION: A control unit of an ocular axial length measurement device executes a past ocular axial length acquisition step, a current ocular axial length measurement step, and a difference information display step. In the past ocular axial length acquisition step, the control unit acquires a measurement result of a past ocular axial length measured for a target subject's eye. In the current ocular axial length measurement step, the control unit measures a current ocular axial length of the target subject's eye. In the difference information display step, the control unit causes a display unit to display difference information, the information relating to a difference between the current ocular axial length measured in the current ocular axial length measurement step and the past ocular axial length acquired in the past ocular axial length acquisition step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an axial length measuring device for measuring the axial length of an eye to be examined, and an axial length measurement result processing program executed by the axial length measuring device.

Background Art

[0002] An axial length measuring device for measuring the axial length of an eye to be examined is known. In a medical examination scene, in addition to the measurement result of the currently measured axial length, it may be useful to present the medical staff with the measurement results of the axial lengths measured in the past for the same eye to be examined. For example, the ophthalmic information processing device described in Patent Document 1 arranges and displays the values of a plurality of axial lengths measured for the same eye to be examined in chronological order according to the examination time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described in Patent Document 1, conventionally, after the measurement of the current axial length of the target eye to be examined is completed, at the stage where the medical staff examines the target eye to be examined, etc., only a plurality of axial lengths are presented to the medical staff by an electronic medical record or the like. Therefore, when the medical staff determines that the measurement result of the axial length is not good as a result of grasping the measurement result of the axial length during the examination, etc., in many cases, the measurement of the axial length is redone even though the subject has already left the axial length measuring device. In addition, conventionally, no technique has been proposed to improve the efficiency of the procedure for measuring the axial length by the axial length measuring device using the measurement results of the axial lengths measured in the past. In the conventional technology, since at least any of the various problems exemplified above could not be solved, it was difficult to appropriately improve the efficiency of medical treatment (examination and diagnosis, etc.) using the measurement result of the axial length.

[0005] A typical object of the present disclosure is to provide an axial length measurement device and an axial length measurement result processing program capable of appropriately improving the efficiency of medical treatment using the measurement result of the axial length.

Means for Solving the Problems

[0006] The axial length measurement device provided by a typical embodiment in the present disclosure is an axial length measurement device for measuring the axial length of an eye to be examined, wherein a control unit of the axial length measurement device executes a past axial length acquisition step of acquiring a measurement result of a past axial length measured for a target eye to be examined, a current axial length measurement step of measuring a current axial length of the target eye to be examined, and a differential information display step of causing a display unit to display differential information which is information regarding a difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step.

[0007] The axial length measurement result processing program provided by a typical embodiment in the present disclosure is an axial length measurement result processing program executed by an axial length measurement device for measuring the axial length of an eye to be examined, and by the axial length measurement result processing program being executed by a control unit of the axial length measurement device, causes the axial length measurement device to execute a past axial length acquisition step of acquiring a measurement result of a past axial length measured for a target eye to be examined, a current axial length measurement step of measuring a current axial length of the target eye to be examined, and a differential information display step of causing a display unit to display differential information which is information regarding a difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step.

[0008] According to the axial length measurement device and the axial length measurement result processing program according to the present disclosure, it becomes easy to appropriately improve the efficiency of medical treatment using the measurement result of the axial length.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0010] <Summary> The control unit of the axial length measuring device exemplified in the present disclosure executes a past axial length acquisition step, a current axial length measurement step, and a difference information display step. In the past axial length acquisition step, the control unit acquires the measurement result of the past axial length measured for the target eye to be examined. In the current axial length measurement step, the control unit measures the current axial length of the target eye to be examined. In the difference information display step, the control unit causes the display unit to display difference information, which is information regarding the difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step.

[0011] According to the technology exemplified in the present disclosure, information regarding the difference between the current axial length and the past axial length of the target eye to be examined (difference information) is displayed by the axial length measuring device. Therefore, a user (at least any one of a doctor, a nurse, a medical technician, etc.) can quickly grasp the state of change in the axial length of the target eye to be examined based on the difference information displayed by the axial length measuring device, and then perform appropriate medical treatment (for example, at least any one of diagnosis, examination, treatment, prescription, etc.). For example, when the user grasps from the difference information that the axial length of the target eye to be examined is rapidly elongating, it is also possible to quickly formulate a treatment policy or an examination policy for suppressing the elongation of the axial length. In addition, when the difference between the current axial length and the past axial length of the target eye to be examined is unnatural, the user can also quickly decide to re-measure the axial length considering the possibility of a defect in the measurement of the current axial length. Therefore, the efficiency of medical treatment using the measurement result of the axial length is likely to be appropriately improved.

[0012] The specific method of the past axial length acquisition step can be appropriately selected. For example, measurement results of a plurality of axial lengths measured in the past for each of a plurality of eyes to be examined may be stored in a storage device. The control unit may acquire data of the measurement result for the target eye to be examined from among the plurality of past measurement results stored in the storage device. The control unit may acquire data of the measurement result for the target eye to be examined from among the plurality of past measurement results stored in the storage device based on information for specifying the target eye to be examined (target patient) (for example, at least any one of an ID, a name, a date of birth, etc.). In addition, the user may input the past measurement result of the target eye to be examined into the axial length measuring device by operating the operation unit or voice input, etc. Note that the model and measurement method, etc. of the axial length measuring device that executes the technology of the present disclosure and the axial length measuring device that measured the axial length of the target eye to be examined in the past may be the same or different.

[0013] After the current axial length of the subject's eye has been measured in the current axial length measurement step, and at least during a part of the time period until the subject's eye is switched to the eye of another subject, the control unit may cause the display unit to display the differential information of the subject's eye. In this case, the differential information will be displayed immediately after the current axial length of the subject's eye has been measured. That is, the differential information is displayed on the display unit at a stage before the subject leaves the axial length measuring device. Therefore, for example, various medical treatments such as re-measurement of the current axial length and omission of additional measurement can be more smoothly performed.

[0014] The axial length measuring device may further include an imaging optical system for imaging an observation image of the subject's eye. The control unit may cause the display unit to display the differential information of the subject's eye together with the observation image captured by the imaging optical system. In this case, the differential information will be displayed immediately after the current axial length of the subject's eye has been measured. That is, the differential information is displayed on the display unit at a stage before the subject leaves the axial length measuring device. Therefore, various medical treatments such as re-measurement of the current axial length for the subject's eye can be more smoothly performed. For example, the control unit can also smoothly perform re-measurement of the axial length based on the observation image displayed together with the differential information.

[0015] The control unit may automatically execute the differential information display step when the measurement of the current axial length of the subject's eye is completed in the current axial length measurement step. In this case, the user can quickly formulate a medical treatment plan, etc. by checking the differential information automatically displayed after the measurement of the current axial length of the subject's eye is completed. Therefore, the efficiency of medical treatment using the measurement result of the axial length is more likely to be further improved.

[0016] However, the control unit may switch whether to automatically display the differential information according to an instruction input by the user. Also, the control unit may switch whether to automatically display the differential information according to whether the differential information satisfies certain conditions (for example, whether the difference is equal to or greater than a threshold value, etc.).

[0017] In the past axial length acquisition step, the control unit may acquire the measurement result of the latest axial length among the measurement results of one or more axial lengths measured in the past for the target eye to be examined. Based on the acquired latest past axial length, the control unit may execute the differential information display step. In this case, the user can grasp the state of the recent change in the axial length of the target eye to be examined. Therefore, the user can perform appropriate medical treatment according to the state of the recent change in the axial length.

[0018] However, based on the measurement result of the axial length that is not the latest among the measurement results of the axial length measured multiple times in the past for the target eye to be examined, the control unit can also execute the differential information display step. Even in this case, the state of the change in the axial length of the target eye to be examined can be appropriately grasped by the user.

[0019] In the differential information display step, the control unit may acquire the elapsed time from the time of measurement of the past axial length acquired in the past axial length acquisition step to the present. The control unit may calculate the change rate of the axial length of the target eye to be examined by dividing the difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step by the elapsed time, and may display the calculated change rate as differential information on the display unit. In this case, the user can more easily and appropriately grasp the state of the change in the axial length of the target eye to be examined by the change rate displayed on the display unit.

[0020] A specific method for calculating the change rate of the axial length can be appropriately selected. For example, the control unit may calculate the change rate of the axial length of the target eye to be examined by dividing the value obtained by subtracting the past axial length from the current axial length by the elapsed time. In this case, the user can easily and appropriately grasp whether the axial length of the target eye to be examined is increasing or not depending on whether the calculated change rate is a positive value.

[0021] The control unit may cause the display unit to display the calculated numerical value of the change rate. Further, the control unit may cause the display unit to display the level (degree) of the calculated change rate. In these cases, the user can grasp the change rate of the axial length of the eye more accurately and intuitively than when a graph or the like showing the change in the axial length of the eye is displayed.

[0022] However, the difference information displayed on the display unit is not limited to the change rate. For example, the control unit may cause the display unit to display, together with the change rate or in place of the change rate, the value or level of the difference between the current axial length measured in the current axial length measurement step and the past axial length obtained in the past axial length acquisition step. Even in this case, the user can appropriately grasp the state of change in the axial length of the target eye to be examined by checking the value of the difference in the axial length displayed on the display unit. Further, the control unit may cause the display unit to display both the value of the current axial length measured in the current axial length measurement step and the value of the past axial length obtained in the past axial length acquisition step as difference information as they are. Even in this case, the user can appropriately grasp the state of change in the axial length of the target eye to be examined by calculating the difference between the displayed values by himself / herself.

[0023] When the current axial length measured in the current axial length measurement step is shorter than the past axial length obtained in the past axial length acquisition step by a certain amount or more, the control unit may execute at least one of a process of re-executing the current axial length measurement step, a process of recommending to the user to re-execute the current axial length measurement step, and a process of recommending to the user to measure the axial length by another method with a different measurement method. Although the axial length often increases with the passage of time, it rarely decreases with the passage of time. Therefore, when the measured current axial length is shorter than the past axial length by a certain amount or more, there is a high possibility that there is a defect in the measurement of the current axial length. Thus, by smoothly causing the user to re-measure the axial length of the same eye to be examined when the current axial length is shorter than the past axial length by a certain amount or more, it becomes easier to further improve the medical treatment efficiency. Note that the degree of "a certain amount or more" may be appropriately determined in consideration of measurement result errors that may occur even when the axial length is measured normally.

[0024] The axial length measuring device may include a light projecting optical system and a light receiving optical system. The light projecting optical system divides the light emitted from the light source and projects the measurement light generated from one of the divided lights toward the fundus of the eye. The light receiving optical system guides the measurement light reflected from the fundus of the eye and the light (interference light) synthesized from the light different from the measurement light among the divided lights to the light receiving element. The axial length measuring device may measure the axial length of the subject eye based on the interference signal output from the light receiving element. That is, the axial length measuring device may be an optical interference type axial length measuring device that measures the axial length of the subject eye based on the principle of optical interference. In this case, the axial length is appropriately measured in a non-contact state with respect to the subject eye. Therefore, it is difficult for the burden on the subject during measurement to increase. Also, as will be described later, the SNR obtained when measuring the axial length by the optical interference type axial length measuring device can also be used for determining the quality of the measurement and the like.

[0025] However, it is also possible to change the method of measuring the axial length employed in the axial length measuring device. For example, a method of measuring the axial length of the subject eye using the principle of ultrasonic waves may be employed. Even in this case, by displaying the difference information between the current axial length and the past axial length, the change state of the axial length of the subject eye can be appropriately and easily grasped. Also, it is possible to apply the technology of the present disclosure to an axial length measuring device capable of measuring the axial length by a plurality of measurement methods (for example, both a method based on the principle of interference light and a method based on the principle of ultrasonic waves).

[0026] The control unit may further execute a past SNR acquisition step and a past SNR display step. In the past SNR acquisition step, the control unit acquires the signal-to-noise ratio of the interference signal when the axial length of the target eye has been measured in the past for the target eye to be examined. In the past SNR display step, the control unit causes the display unit to display the information on the signal-to-noise ratio acquired in the past SNR acquisition step. The signal-to-noise ratio (SNR) is the amount of noise with respect to the interference signal and is expressed logarithmically. The larger the SNR, the less noise and the higher the likelihood of acquiring a high-quality interference signal. For example, when the subject is a child and fixation is insufficient, the SNR tends to be small. Therefore, when the subject is a child and the displayed past SNR is small, the user can also improve the measurement accuracy of the axial length by calling on the subject to fixate on the fixation mark. Also, when the eye to be examined has a disease such as cataract, the SNR also tends to be small. Therefore, when the subject has a disease such as cataract and the displayed past SNR is small, the user can also decide to abandon the measurement of the axial length by the optical coherence axial length measuring device early and change to measurement by another method (for example, ultrasonic method, etc.) that is less affected by the disease. Thus, the medical treatment is more likely to proceed appropriately.

[0027] Note that the specific method for causing the display unit to display the past SNR of the target eye to be examined can be selected as appropriate. For example, the control unit may cause the display unit to display the value of the past SNR of the target eye to be examined, or may cause the display unit to display an index indicating the level (degree) of the past SNR. Also, when the value of the past SNR of the target eye to be examined is equal to or greater than a reference value, the control unit may execute at least one of a process of recommending, by display or voice, etc., calling on the subject to fixate on the fixation mark, and a process of recommending, by display or voice, etc., measurement by another method.

[0028] The control unit may further execute a current SNR acquisition step of acquiring the signal-to-noise ratio of the interference signal when the current axial length is measured in the current axial length measurement step. When the signal-to-noise ratio acquired in the current SNR acquisition step is less than the reference value, the control unit may execute at least one of the following processes: re-executing the current axial length measurement step, recommending to the user to re-execute the current axial length measurement step, and recommending to the user to measure the axial length by another method with a different measurement method. As described above, when the fixation of the target eye to be examined is insufficient and when the eye to be examined has a disease such as cataract, etc., the SNR tends to be small. Therefore, when the SNR at the time of measuring the current axial length is less than the reference value, by smoothly causing the user to re-measure the axial length of the same eye to be examined, etc., the medical treatment efficiency is more likely to be improved.

[0029] Further, the present invention can also be expressed as follows. An axial length measurement result processing method, comprising: a past axial length acquisition step of acquiring the measurement result of the past axial length measured for a target eye to be examined; a current axial length measurement step of measuring the current axial length of the target eye to be examined; and a difference information display step of causing a display unit to display difference information, which is information regarding the difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step. The axial length measurement result processing method is characterized by including the above steps.

[0030] <Embodiment> Hereinafter, one of the typical embodiments according to the present disclosure will be described. The axial length measurement device 1 measures the axial length of the eye to be examined E. The axial length measurement device 1 of the present embodiment is an optical interference type axial length measurement device that measures the axial length of the eye to be examined E based on the principle of optical interference. However, as described above, at least a part of the technology in the present disclosure can also be adopted in an axial length measurement device that measures the axial length of the eye to be examined E using a principle other than optical interference (for example, the principle of ultrasonic waves, etc.).

[0031] (Device Configuration) Referring to FIG. 1, the configuration of the optical system and the control system of the axial length measuring device 1 according to the present embodiment will be described. The axial length measuring device 1 includes an axial length measuring optical system (measurement unit) 10, a keratometric projection optical system 40, an alignment projection optical system 50, and an anterior eye segment front imaging optical system 30.

[0032] The keratometric projection optical system 40 projects an index for corneal shape measurement onto the cornea. The keratometric projection optical system 40 includes a ring-shaped light source 41 disposed around the measurement optical axis L1. The ring index projected onto the cornea EC of the eye to be examined E by the light source 41 is used to measure characteristics of the eye to be examined E based on the corneal shape (for example, at least any one of curvature and astigmatic axis angle, etc.). Note that, for the light source 41, for example, an LED that emits infrared light or visible light can be used.

[0033] The alignment projection optical system 50 projects an alignment index onto the cornea EC of the eye to be examined E. The alignment projection optical system 50 includes a light source 51 disposed inside the light source 41. The light source 51 emits infrared light. Note that the light sources 41 and 51 also serve as illumination light sources for illuminating the anterior segment of the eye to be examined E.

[0034] The anterior eye segment front imaging optical system 30 captures a front view image of the anterior segment of the eye to be examined E. The anterior eye segment front imaging optical system 30 includes a dichroic mirror 33, an objective lens 47, a total reflection mirror 36, a filter 34, an imaging lens 37, and a two-dimensional imaging element 35. The imaging surface of the two-dimensional imaging element 35 is disposed at a position substantially conjugate to the anterior segment of the eye to be examined E. Also, the anterior eye segment front imaging optical system 30 can capture a red reflex image (image inside the pupil) in the pupil part of the eye to be examined E illuminated by the fundus reflex light. The dichroic mirror 33 transmits most of the measurement light and reflects a part of the measurement light. The light from the light sources 41 and 51 is reflected by the dichroic mirror 33 and imaged on the two-dimensional imaging element 35 via the objective lens 47, the total reflection mirror 36, the filter 34, and the imaging lens 37.

[0035] The axial length measurement optical system 10 projects measurement light (first measurement light) onto the eye to be examined E and detects interference light caused by the reflected light thereof. The axial length measurement optical system 10 includes a light projection optical system 10A and a light reception optical system 10B. The light projection optical system 10A divides the light emitted from the measurement light source 2 (which also serves as a fixation lamp in this embodiment), and projects the first measurement light generated from one of the divided lights toward the fundus of the eye to be examined E. The light projection optical system 10A includes a collimator lens 3, a beam splitter 5, a first triangular prism (corner cube) 7, a second triangular prism 9, a polarization beam splitter 11, a quarter-wave plate 18, and a diffuser plate 13. The collimator lens 3 makes the light beam of the low-coherence light emitted from the measurement light source 2 into a parallel light beam. The beam splitter 5 divides the parallel light beam emitted from the measurement light source 2 and passing through the collimator lens 3. The first triangular prism 7 is arranged in the transmission direction of the beam splitter 5. The second triangular prism 9 is arranged in the reflection direction of the beam splitter 5. The diffuser plate 13 is an optical member that randomly diffuses light.

[0036] The diffuser plate 13 is arranged in the optical path of the light projection optical system 10A and is used as a speckle suppression means for optically suppressing the speckle noise generated in the fundus illumination image. In this embodiment, the diffuser plate 13 is located at a position outside the optical path of the anterior eye frontal imaging optical system 30 and is arranged in the common optical path through which the first measurement light and the second measurement light (described later) pass. That is, in order to remove the speckle noise in the fundus illumination image, it is inserted into the optical path during fundus illumination imaging and vibrated in a direction perpendicular to the optical axis L1. In this embodiment, the diffuser plate 13 vibrates in a direction perpendicular to the optical axis L1, but the diffuser plate 13 may be rotated. The first drive unit 16 inserts the diffuser plate 13 into the optical path and removes the diffuser plate 13 from the optical path. The second drive unit 15 vibrates the diffuser plate 13 inserted into the optical path in a direction perpendicular to the optical axis.

[0037] The light-receiving optical system 10B combines the first measurement light reflected from the fundus of the eye E to be examined and the light split by the beam splitter 5 (second measurement light different from the first measurement light), and guides the combined light to the light-receiving element 21. The light-receiving optical system 10B includes a dichroic mirror 33, a quarter-wave plate 18, a polarization beam splitter 11, a condenser lens 19, and a light-receiving element 21.

[0038] The light (linearly polarized light) emitted from the measurement light source 2 is collimated by the collimator lens 3 and then split into the first measurement light and the second measurement light by the beam splitter 5. The split first measurement light is reflected and folded back by the first triangular prism 7. The split second measurement light is reflected and folded back by the second triangular prism 9. The folded first measurement light and second measurement light are combined by the beam splitter 5. The combined light is reflected by the polarization beam splitter 11 and converted into circularly polarized light by the quarter-wave plate 18, and then irradiated onto at least the cornea EC and the fundus of the eye E to be examined through the diffuser plate 13 and the dichroic mirror 33. The 1 / 2 wavelength phase of the measurement light beam is converted by being reflected by the cornea and the fundus of the subject's eye.

[0039] The corneal reflection light and the fundus reflection light pass through the dichroic mirror 33 (a part of the fundus reflection light is reflected) and the diffuser plate 13, and are converted into linearly polarized light by the quarter-wave plate 18. Then, the reflected light that has passed through the polarization beam splitter 11 is condensed by the condenser lens 19 and then received by the light-receiving element 21. The axial length measuring device 1 measures the axial length of the eye E to be examined based on the interference signal output from the light-receiving element 21.

[0040] The first triangular prism 7 is an optical member (optical path length changing member) arranged to be movable in the optical axis direction in order to adjust the optical path difference between the first measurement light and the second measurement light. The first triangular prism 7 moves linearly in the optical axis direction with respect to the beam splitter 5 by the drive of the drive unit 61 (for example, a motor). In this case, the optical path length changing member may be a triangular mirror. Further, the drive position of the first triangular prism 7 is detected by a position detection sensor 62 (for example, a potentiometer or an encoder, etc.).

[0041] Note that the axial length measuring device 1 of the present embodiment interferes the corneal reflected light and the fundus reflected light, but it is also possible to change the interference method. For example, the axial length measuring device may include a beam splitter (optical splitting member) that splits the light emitted from the measurement light source 2, a sample arm, a reference arm, and a light receiving element for receiving the interference light. The axial length measuring device may include an optical interference optical system that causes the light receiving element to receive the interference light formed by the measurement light irradiated to the eye E to be examined via the sample arm and the reference light from the reference arm. In this case, an optical path length changing member is arranged in at least one of the sample arm and the reference arm.

[0042] The control unit 4 includes a controller (CPU in the present embodiment) and performs overall control of the axial length measuring device 1 and processes such as calculation of measurement results. The control unit 4 is connected to the measurement light source 2, the light source 41, the light source 51, the first drive unit 16, the second drive unit 15, the light receiving element 21, the imaging element 35, the display unit 70, the non-volatile memory 75, etc. Further, an operation unit 78 for performing various input operations is connected to the control unit 4. The display unit 70 displays various images. Various control programs, data, etc. are stored in the memory 75. For example, an axial length measurement result processing program for executing the measurement process (see FIG. 2) described later may be stored in the memory 75.

[0043] The memory 75 may store measurement results of a plurality of axial lengths of the eyes that have been measured in the past for each of a plurality of eyes to be examined (in this embodiment, information such as SNR at the time of measurement is also included) in a storage device. In this case, the control unit 4 can acquire the measurement results of the past axial lengths stored in the memory 75. Further, the measurement results of the plurality of axial lengths measured in the past may be stored in a storage device different from the axial length measuring device 1 (for example, at least any one of a server, a personal computer, and an external hard disk, etc.). In this case, the control unit 4 may acquire the measurement results of the past axial lengths from another storage device via wired communication, wireless communication, a network, a removable memory, or the like.

[0044] (Measurement process) With reference to FIGS. 2 to 4, the measurement process executed by the axial length measuring device 1 of this embodiment will be described. In the measurement process of this embodiment, information regarding the difference between the current axial length measured for the target eye to be examined and the past axial length measured for the same target eye to be examined (hereinafter referred to as "difference information") is displayed on a measurement screen 80 (see FIG. 3) displayed when measuring the axial length of the target eye to be examined, and a confirmation screen 90 (see FIG. 4) for allowing the user to confirm the measurement result of the target eye to be examined. The measurement process illustrated in FIG. 2 is executed by the control unit 4 of the axial length measuring device 1 according to the axial length measurement result processing program stored in the memory 75.

[0045] As shown in FIG. 2, the control unit 4 determines whether an instruction to start measuring the axial length has been input (S1). In this embodiment, an instruction to start the measurement is input by inputting information for identifying the subject whose axial length is to be measured into the axial length measuring device 1. For example, the user may operate the operation unit 78 to input information for identifying the subject (for example, at least any one of the subject's ID, name, etc.) to input an instruction to start the measurement. Further, the user may input an instruction to start the measurement by having an identifier associated with information for identifying the patient read by an identification reading unit (not shown). If an instruction to start the measurement has not been input (S1: NO), the process of S1 is repeated and the device enters a standby state.

[0046] When an instruction to start measurement is input (S1: YES), the control unit 4 causes the measurement screen 80 (see FIG. 3) to be displayed on the display unit, and identifies the target eye to be examined (that is, either the left eye or the right eye of the subject whose eye axis length is to be measured) (S2). For example, the control unit 4 may identify the target eye to be examined based on the information input in S1.

[0047] Referring to FIG. 3, an example of the measurement screen 80 displayed when measuring the eye axis length will be described. The measurement screen 80 illustrated in FIG. 3 is provided with a subject information display unit 81, a current eye axis length display unit 82, a current SNR display unit 83, a difference display unit 85, a past SNR display unit 86, a change rate display unit 87, and an anterior segment frontal view observation image display unit 89. The control unit 4 causes the information of the subject identified in S2 to be displayed on the subject information display unit 81. The control unit 4 causes the anterior segment frontal view observation image of the target eye to be examined captured by the anterior segment frontal imaging optical system 30 to be displayed on the anterior segment frontal view observation image display unit 89. Explanation of the other display units will be described later.

[0048] The control unit 4 acquires information regarding the measurement results of the past eye axis lengths measured for the target eye to be examined identified in S2 (S3). As an example, in the present embodiment, the measurement results of the plurality of eye axis lengths measured in the past for each of the plurality of eyes to be examined are associated with the SNR (signal-to-noise ratio) at the time of measurement and the date and time when the measurement was performed, and are stored in a storage device (for example, the memory 75 or the like). In S3 of the present embodiment, the control unit 4 acquires the measurement results (values of the eye axis length) of the past eye axis lengths regarding the target eye to be examined identified in S2, the SNR (hereinafter referred to as "past SNR") when the eye axis length was measured in the past, and the measurement date and time from among the stored measurement results of the plurality of eye axis lengths.

[0049] In addition, when there are multiple past measurement results of the axial length of the target eye to be examined specified in S2, the control unit 4 acquires the latest measurement result among the multiple measurement results. As a result, by performing S9 to S12 described later, the state of the most recent change in the axial length of the target eye to be examined can be more easily grasped by the user. However, it is also possible to change the processing of S3. For example, past information regarding the target eye to be examined may be input via an operation of the operation unit 78 or the like.

[0050] The control unit 4 causes the display unit 70 to display the past SNR of the target eye to be examined acquired in S3 (S4). As an example, in the present embodiment, the past SNR of the target eye to be examined acquired in S3 is displayed in the past SNR display unit 86 formed in the measurement screen 80. The larger the SNR when measuring the axial length, the less noise there is and the higher the likelihood of acquiring a high-quality interference signal. For example, when the subject is a child and fixation is insufficient, the SNR tends to be small. Therefore, when the subject is a child and the past SNR displayed in the past SNR display unit 86 is small, the user can also improve the measurement accuracy of the axial length by calling on the subject to fixate on the fixation mark. Also, when the eye to be examined has a disease such as cataract, the SNR also tends to be small. Therefore, when the target eye to be examined has a disease such as cataract and the past SNR displayed in the past SNR display unit 86 is small, the user can decide to give up the measurement of the axial length by the optical coherence axial length measuring device early (S7: YES) and change to measurement by another method (for example, the ultrasonic method etc.) that is less affected by the disease. Thus, the medical treatment is more likely to proceed appropriately.

[0051] In addition, in S4 of the present embodiment, the past SNR values are displayed on the display unit 70. However, it is also possible to change the method of displaying the past SNR. For example, the control unit 4 may cause the display unit 70 to display an index or the like indicating the level (degree) of the past SNR. Further, when the past SNR value of the target eye to be examined is equal to or greater than a reference value, the control unit 4 may execute at least one of a process of recommending, by display or voice or the like, that the subject fixate on the fixation mark, and a process of recommending, by display or voice or the like, measurement by another method. In this case, the medical treatment is more likely to proceed smoothly.

[0052] Next, the control unit 4 determines whether a trigger for executing the measurement has been input (S6). If not input (S6: NO), it is determined whether an instruction to end the axial length measurement process for the target eye to be examined has been input (S7). If not input (S7: NO), the process returns to S6, and the processes of S6 and S7 are repeated. When an instruction to end the measurement process is input (S7: YES), the axial length measurement process for the target eye to be examined is ended (for example, a process of ending the display of the measurement screen 80 for the target eye to be examined is executed), and the process returns to S1. As described above, the user can also end the measurement process midway when the past SNR displayed on the past SNR display unit 86 is small and the user wants to quickly switch to measurement of the axial length by another method.

[0053] When a trigger for executing the measurement is input (S6: YES), the control unit 4 measures the current axial length of the target eye to be examined and acquires the SNR (hereinafter referred to as "current SNR") when the current axial length is measured (S9). The control unit 4 causes the current axial length of the target eye to be examined measured in S9 to be displayed on the current axial length display unit 82 of the measurement screen 80 (see FIG. 3). Further, the control unit 4 causes the current SNR acquired in S9 to be displayed on the current SNR display unit 83 of the measurement screen 80 (see FIG. 3).

[0054] The control unit 4 calculates the difference between the past axial length of the target eye to be examined acquired in S2 and the current axial length of the target subject to be examined measured in S9 (in this embodiment, the value obtained by subtracting the past axial length from the current axial length), and causes it to be displayed on the display unit 70 (specifically, the difference display unit 85 of the measurement screen 80) (S10). Therefore, the user can quickly grasp the state of change in the axial length of the target eye to be examined based on the difference between the past axial length and the current axial length displayed by the axial length measuring device 1, and perform appropriate medical treatment (for example, at least any one of examination, inspection, treatment, and prescription, etc.).

[0055] In particular, in this embodiment, for the target eye to be examined specified in S2, when there are a plurality of past measurement results of the axial length, the difference between the latest measurement result among the plurality of measurement results and the current measurement result is displayed. Therefore, the user can grasp the state of the most recent change in the axial length of the target eye to be examined by checking the difference displayed on the difference display unit 85. Note that in S10, the value of the difference between the past axial length and the current axial length itself may be displayed, or a value indicating the level (degree) of the difference value may be displayed.

[0056] The control unit 4 calculates the elapsed time from the time of measurement of the past axial length acquired in S3 until the present (S11). The control unit 4 divides the difference between the past axial length of the target eye to be examined acquired in S2 and the current axial length of the target subject to be examined measured in S9 by the elapsed time calculated in S11 to calculate the change speed of the axial length of the target eye to be examined, and causes it to be displayed on the display unit 70 (specifically, the change speed display unit 87 of the measurement screen 80) (S12). Therefore, the user can more easily and appropriately grasp the state of change in the axial length of the target eye to be examined based on the change speed displayed on the change speed display unit 87.

[0057] Specifically, in S12 of this embodiment, the change speed of the axial length is calculated by dividing the value obtained by subtracting the past axial length from the current axial length by the elapsed time. Therefore, the user can easily and appropriately grasp whether the axial length of the target eye to be examined is increasing or not based on whether the change speed displayed on the change speed display unit 87 is a positive value.

[0058] In this embodiment, for the target eye to be examined identified in S2, when there are multiple past measurement results of the axial length of the eye, the rate of change of the axial length is calculated based on the latest measurement result among the multiple measurement results. Therefore, the user can grasp the state of the most recent change in the axial length of the target eye to be examined by checking the rate of change of the axial length displayed on the rate-of-change display unit 87.

[0059] In this embodiment, the control unit 4 causes the rate-of-change display unit 87 to display the calculated numerical value (mm / year) of the rate of change. Therefore, the user can grasp the rate of change of the axial length more accurately and intuitively compared to the case where a graph or the like showing the change in the axial length is displayed. However, it is also possible to change the specific display method of the rate of change. For example, the control unit 4 may cause the rate-of-change display unit 87 to display the level (degree) of the calculated rate of change. Even in this case, the user can grasp the rate of change of the axial length more accurately and intuitively.

[0060] As described above, when the measurement of the current axial length of the target eye to be examined is completed in S9, the control unit 4 of this embodiment automatically causes the difference (S10) and the rate of change (S12) to be displayed on the display unit 70. In this embodiment, both the difference displayed in S10 and the rate of change to be displayed in S12 are examples of difference information regarding the difference between the current axial length and the past axial length. The user can quickly formulate a diagnosis and treatment policy or the like by checking the difference information automatically displayed after the measurement of the current axial length of the target eye to be examined is completed. Therefore, the efficiency of the diagnosis and treatment using the measurement result of the axial length is more likely to be further improved.

[0061] When the processes of S9 to S12 are completed, the control unit 4 switches the measurement screen 80 (see FIG. 3) being displayed on the display unit 70 to a confirmation screen 90 (see FIG. 4). As shown in FIG. 4, also on the confirmation screen 90 of the present embodiment, various types of information are displayed in each of the current axial length display unit 82, the current SNR display unit 83, the difference display unit 85, the past SNR display unit 86, and the change rate display unit 87, in the same manner as the measurement screen 80 described above. Therefore, the user can appropriately grasp the state of the change in the axial length of the target eye to be examined also on the confirmation screen 90.

[0062] Next, the control unit 4 determines whether the current axial length measured in S9 is shorter than the past axial length acquired in S3 by a certain amount or more (that is, whether the axial length of the target eye to be examined is atrophied) (S14). Although the axial length often increases with the passage of time, it is rare for it to decrease with the passage of time. Therefore, when the measured current axial length is shorter than the past axial length by a certain amount or more (when the axial length is significantly atrophied) (S14: YES), there is a high possibility that there is a defect in the measurement of the current axial length. In this case, the control unit 4 executes at least any one of the process of measuring the axial length again (S9), the process of recommending to the user to measure the axial length again, and the process of recommending to the user to measure the axial length by another method with a different measurement method (S16). As a result, it becomes easier to further improve the medical treatment efficiency. After that, the process proceeds to S18.

[0063] Note that even when the axial length is measured normally, an error may occur in the measurement result. Therefore, in S3, the control unit 4 takes into account the error during measurement and determines that the axial length is atrophied when the value obtained by subtracting the past axial length from the current axial length is smaller than a predetermined negative threshold value. As a result, it becomes easier to appropriately eliminate the influence of the measurement error when measured normally.

[0064] Also, when the measured current axial length of the eye is not shorter than a certain length compared to the past axial length of the eye (when the axial length of the eye has not significantly atrophied) (S14: NO), it is determined whether the SNR obtained at the time of measuring the current axial length in S9 is less than the reference value (S15). As described above, when the fixation of the subject eye is insufficient and when the subject eye has a disease such as cataract, the SNR tends to be small. Therefore, when the current SNR is less than the reference value (S15: YES), the control unit 4 executes at least one of the process of measuring the axial length again (S9), the process of recommending to the user to measure the axial length again, and the process of recommending to the user to measure the axial length by another method with a different measurement method (S16). As a result, the medical treatment efficiency is more likely to be further improved. Then, the process proceeds to S18.

[0065] The control unit 4 determines whether an instruction to measure the axial length of the same subject eye again has been input (S18). If not (S18: NO), it is determined whether an instruction to end the axial length measurement process for the subject eye has been input (S19). If not (S19: NO), the process returns to S18, and the processes of S18 and S19 are repeated. When an instruction to measure the axial length of the same subject eye again is input (S18: YES), the control unit 4 returns the confirmation screen 90 (see FIG. 4) displayed on the display unit 70 to the measurement screen 80 (see FIG. 3), and measures the axial length of the same subject eye again (S9 to S16). When an instruction to end the measurement process is input (S19: YES), the axial length measurement process for the subject eye is ended (for example, a process of ending the display of the confirmation screen 90 for the subject eye is executed), and the process returns to S1.

[0066] As described above, after the current axial length has been measured in S9, and at least during a part of the time period until the target eye to be examined is switched to the eye to be examined of another subject (S19: YES), the control unit 4 causes the display unit 70 to display the differential information of the target eye to be examined (in this embodiment, the difference calculated in S10 and the change rate calculated in S12). As a result, the differential information will be displayed by the axial length measuring device 1 immediately after the current axial length of the target eye to be examined has been measured. That is, the differential information is displayed on the display unit 70 before the subject leaves the axial length measuring device 1. Therefore, for example, various medical treatments such as re-measurement of the current axial length and omission of additional measurement can be more smoothly performed.

[0067] As shown in FIG. 3, the control unit 4 causes the display unit 70 to display the differential information of the target eye to be examined together with the frontal view observation image (an example of an observation image) of the anterior segment of the target eye to be examined E captured by the anterior segment frontal imaging optical system (an example of an imaging optical system) 30. As a result, the differential information will be displayed by the axial length measuring device 1 immediately after the current axial length of the target eye to be examined has been measured. That is, the differential information is displayed on the display unit 70 before the subject leaves the axial length measuring device 1. Therefore, for example, various medical treatments such as re-measurement of the current axial length and omission of additional measurement can be more smoothly performed.

[0068] The technology disclosed in the above embodiment is merely an example. Therefore, it is also possible to change the technology exemplified in the above embodiment. For example, among the plurality of processes exemplified in the above embodiment, it is also possible to cause only a part of the processes to be executed by the axial length measuring device 1. For example, the axial length measuring device 1 may execute only the process (S12) of displaying the change rate of the axial length without performing the process (S10) of displaying the difference between the past and current axial lengths.

[0069] Note that the process of obtaining the measurement result of the past axial length of the target eye to be examined in S3 of FIG. 2 is an example of the "past axial length acquisition step". The process of measuring the current axial length of the target eye to be examined in S9 is an example of the "current axial length measurement step". The process of causing the display unit 70 to display the difference information between the current axial length and the past axial length in S10 to S12 is an example of the "difference information display step". The process of obtaining the SNR at the time of measuring the past axial length of the target eye to be examined in S3 is an example of the "past SNR acquisition step". The process of causing the past SNR to be displayed on the display unit 70 in S4 is an example of the "past SNR display step". The process of obtaining the SNR at the time of measuring the current axial length in S9 is an example of the "current SNR acquisition step".

Explanation of Signs

[0070] 1 Axial length measuring device 4 Control unit 10 Axial length measurement optical system 10A Light projection optical system 10B Light receiving optical system 21 Light receiving element 70 Display unit 75 Memory 80 Measurement screen 82 Current axial length display unit 83 Current SNR display unit 85 Difference display unit 86 Past SNR display unit 87 Change speed display unit 90 Confirmation screen

Claims

1. An axial length measuring device for measuring the axial length of an eye to be examined, The control unit of the axial length measuring device, A past axial length acquisition step of acquiring a measurement result of a past axial length measured for a target eye to be examined; A current axial length measurement step of measuring the current axial length of the target eye to be examined; A differential information display step of causing a display unit to display differential information, which is information regarding a difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step; An axial length measuring device, characterized by executing the above steps.

2. The axial length measuring device according to Claim 1, The control unit causes the display unit to display the differential information of the target eye to be examined in at least a part of the time period after the current axial length is measured in the current axial length measurement step and until the target eye to be examined is switched to the eye to be examined of another subject. An axial length measuring device characterized by the above.

3. The axial length measuring device according to Claim 1 or 2, Further comprising an imaging optical system for imaging an observation image of the target eye to be examined, The control unit causes the display unit to display the differential information of the target eye to be examined together with the observation image captured by the imaging optical system. An axial length measuring device characterized by the above.

4. The axial length measuring device according to any one of Claims 1 to 3, The control unit automatically executes the differential information display step when the measurement of the current axial length of the target eye to be examined is completed in the current axial length measurement step. An axial length measuring device characterized by the above.

5. The axial length measuring device according to any one of Claims 1 to 4, The control unit, In the past axial length acquisition step, among the measurement results of one or more axial lengths measured in the past for the target eye to be examined, the measurement result of the latest axial length is acquired, An axial length measuring device, characterized in that the difference information display step is executed based on the latest acquired past axial length.

6. An axial length measuring device according to any one of claims 1 to 5, In the difference information display step, the control unit acquires the elapsed time from the time of measurement of the past axial length acquired in the past axial length acquisition step to the present, divides the difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step by the elapsed time to calculate the change rate of the axial length of the target eye to be examined, and causes the display unit to display the calculated change rate as the difference information. An axial length measuring device characterized by this.

7. An axial length measuring device according to any one of claims 1 to 6, The control unit When the current axial length measured in the current axial length measurement step is shorter than the past axial length acquired in the past axial length acquisition step by a certain amount or more, a process of re-executing the current axial length measurement step, a process of recommending to the user to re-execute the current axial length measurement step, and a measurement method different from the current measurement method. An axial length measuring device characterized by executing at least one of the processes of recommending to the user the measurement of the axial length by another method.

8. An axial length measuring device according to any one of claims 1 to 7, a light projecting optical system that splits the light emitted from a light source and projects the measurement light generated from one of the split lights toward the fundus of the eye; a light receiving optical system that guides the light synthesized by the measurement light reflected from the fundus of the eye and the light different from the measurement light among the split lights to a light receiving element; An axial length measuring device comprising: measuring the axial length of an eye to be examined based on an interference signal output from the light receiving element.

9. The axial length measuring device according to claim 8, wherein the control unit a past SNR acquisition step of acquiring a signal-to-noise ratio of an interference signal when the axial length of the target eye to be examined was measured in the past; a past SNR display step of causing the display unit to display information on the signal-to-noise ratio acquired in the past SNR acquisition step; The axial length measuring device further characterized by further executing.

10. The axial length measuring device according to claim 8 or 9, wherein the control unit executes a current SNR acquisition step of acquiring a signal-to-noise ratio of an interference signal when the current axial length is measured in the current axial length measurement step; When the signal-to-noise ratio acquired in the current SNR acquisition step is less than a reference value, at least one of a process of re-executing the current axial length measurement step, a process of recommending to the user to re-execute the current axial length measurement step, and a process of recommending to the user to measure the axial length by another method with a different measurement method is executed. The axial length measuring device is characterized by this.

11. An axial length measurement result processing program executed by an axial length measuring device for measuring the axial length of an eye to be examined, By the axial length measurement result processing program being executed by the control unit of the axial length measuring device, a past axial length acquisition step of acquiring a measurement result of a past axial length measured for a target eye to be examined; a current axial length measurement step of measuring the current axial length of the target eye to be examined; a difference information display step of causing the display unit to display difference information which is information regarding the difference between the current axial length measured in the current axial length measurement step and the past axial length acquired in the past axial length acquisition step; An axial length measurement result processing program, characterized by causing the axial length measurement device to execute

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