JPH0554324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an eye refractive power measurement device that can objectively measure the accommodative power of an eye to be examined.

Prior Art Conventionally, visual acuity test indicators are made visible to the subject's eye through a corrective lens that can convert the refractive power.
A subjective eye refractive power measurement device is known that measures the distance refractive power of the eye to be examined based on the responses of the eye to be examined.
In addition, a measurement target image is photoelectrically detected on the fundus of the eye to be examined, the measurement target image is projected onto the fundus of the eye to be examined, this measurement target image is detected photoelectrically, and the distance refractive power of the eye to be examined is objectively determined. Objective refractive power measurement devices are also known.

By the way, in eye refractive power measurement, it is necessary not only to measure the distance refractive power but also to measure whether the eye to be examined can exert an accommodative power up to the near point position.

In this case, in the conventional apparatus described above, the refractive power of the eye to be examined is corrected based on the distance refractive power obtained by measurement, and in this state, the visual acuity test chart is moved to the near point position, and the visual acuity test chart is moved to the near point position. Accommodative power was measured based on the subject's responses.

Problems to be Solved by the Invention However, in this type of accommodative measurement, the accommodative force is measured only by the response of the subject, and the subject himself or herself does not know how much accommodative force is actually working. This made it difficult to accurately measure the accommodation force.

Means for Solving the Problems In order to solve the problems of the prior art, the present invention provides a chart projection system for projecting a chart image for examination onto the fundus of the eye to be examined using visible light, and a chart projection system for projecting a chart image for examination onto the fundus of the eye to be examined. The system is equipped with a measurement target projection system for projecting a measurement target image onto the fundus of the eye using invisible light, and an observation system for converting the measurement target image into a visible image for observation. The measurement target image is configured to be able to change the focus state and to change the focus state of the measurement target image, and to be observed in the observation system after the focus state of the inspection chart image is changed. The present invention is characterized in that it includes an accommodation force measurement system that measures accommodation force based on changes in the focused state of the target image.

Function: An index plate placed at the far point position is projected onto the fundus of the eye to be examined as a measurement target image using invisible light.
At the same time, a chart image placed at the far point position is projected onto the fundus of the subject's eye using visible light, and then the chart plate or projection lens of the chart projection system is moved toward the near point position, thereby splitting the measurement target image. If the position where observation begins is defined as the near point position, the difference between the near point position and the far point position corresponds to the accommodation force.

Embodiments Below, embodiments of the eye refractive power measuring device according to the present invention will be described based on the drawings.

FIG. 1 is a diagram showing an optical system of an eye refractive power measuring device according to the present invention.

In FIG. 1, 1 is a target image projection system, 2 is a target image projection system;
3 is an imaging optical system, 3 is a common optical system shared by the target image projection system 1 and the imaging optical system 2, 4 is a chart projection system, 5 is an aiming optical system, 6 is the eye to be examined, and 7 is the anterior segment of the eye. It is. The target image projection system 1 has the function of projecting target light onto the fundus 8 of the subject's eye 6 via the shared optical system 3 to form a target image of the fundus 8, and includes a light emitting element 9, a condenser lens 10 , index plate 11, reflective prism 1
2, 13, relay lens 14, reflective prism 1
5. It is roughly constituted by a half-moon aperture plate 16.
Here, the light emitting element 10 emits infrared light, which is invisible light, and this infrared light is converted into a parallel light beam by the condenser lens 10 and illuminates the index plate 11. As shown in FIG. 2, the index plate 11 has slits 11a to 11d formed therein and four deflection prisms 11e to 11h attached thereto. Thereby, the index plate 11 is illuminated with infrared light to form a measurement target light, and the polarizing prisms 11e to 11h polarize the target light in a direction perpendicular to the longitudinal direction of the slit.

On the other hand, the shared optical system 3 includes a slit prism 1
7, image rotator 18, objective lens 19,
It consists of a beam splitter 20. and,
The target light from the indicator plate 11 is reflected by the reflecting prisms 12, 13, and 15 and passes through the half-moon diaphragm plate 1.
6, passing through the meniscal foramen 16a and 16b,
It is reflected by the reflective surface 17a of the slit prism 17, and then passes through the image rotator 18, objective lens 19, and beam splitter 20 to the subject's eye 6.
The light passes through the pupil of the eye and is projected onto the fundus 8. The half-moon diaphragm plate 16 is arranged in relation to the objective lens 19 so as to be conjugate with the pupil position of the eye 6 to be examined at an appropriate position, and blocks reflected light harmful to measurement from the anterior segment 7 of the eye 6 to be examined. This allows light to enter the eye 6 to be examined. Also,
The image rotator 18 is connected to the optical axis l of the shared optical system 3.
By rotating by an angle of θ/2 around
The measurement target image formed on the fundus 8 is rotated by an angle θ in the meridian direction of the eye 6 to be examined.

The reflected light of the measurement target image projected onto the fundus 8 is transmitted through a beam splitter 20, an objective lens 19,
The light is guided to the imaging optical system 2 via the slit hole 19a of the slit prism 19, the aperture 21a formed in the center of the aperture diaphragm plate 21, the relay lens 22, and the reflection prism 23. Also,
The aperture diaphragm plate 21 is arranged at a position conjugate with the pupil of the eye 6 to be examined, and is adapted to guide reflected light passing through the center of the pupil to the relay lens 22. Furthermore, the imaging optical system 2 is roughly composed of a reflecting mirror 24, a movable lens 25, a reflecting mirror 26, a half mirror 27, and an imaging lens 28, and it receives the reflected light of the measurement target image formed on the fundus 8. The light is guided to a photocathode 29a of the imaging device 29, and a measurement target image is formed on the photocathode 29a. Here, when the image rotator 18 is rotated by an angle θ/2 around the optical axis l as described above,
The measurement target image is designed to rotate by an angle θ in the rotation direction, but since the reflected light of the measurement target image reflected at the fundus 8 passes through the image rotator 18 again, the rotation direction of the image rotator 18 and The measurement target image is rotated by an angle θ in the opposite direction, and a measurement target image facing a predetermined direction is formed on the photocathode 29a of the imaging device 29, regardless of the rotation of the image rotator 18. ing.

The chart projection system 4 includes a tungsten lamp 30 as a visible light source, a color correction filter 31, a condenser lens 32, a chart plate 33, and a moving lens 3.
4, reflective mirrors 36, 37, relay lens 38,
It is roughly composed of a reflecting mirror 39 and an objective lens 40. Here, the chart plate 33 is illuminated by a tungsten lamp 30 via a condenser lens 31 and a color correction filter 32, and the wavelength of the light emitted from the tungsten lamp 30 is selected by the color correction filter 32, and the wavelength is 400 nm.
Only visible light from 700nm to 700nm is transmitted. A chart 33a as shown in FIG. 3 is formed on this chart board 33, and the light from the chart 33a is guided to a moving lens 34 and a relay lens 38, and a reflecting mirror 36,
The optical path is changed by 37 and 39, and the relay lens 3
8 and an objective lens 40, the beam is guided to a beam splitter 41, and is projected toward the subject's eye 6 via the beam splitter 20. Further, the movable lens 34 is disposed so as to be movable in the direction of its optical axis, and in the case of objective measurement, the eye 6 to be examined is placed in a position where the eye 6 is viewed from a distance or in a mist view, depending on the refractive power of the eye 6 to be examined. It is arranged in such a way that measurement can be performed in a state where the accommodation power of the eye 6 to be examined is removed.

Furthermore, the aiming optical system 5 is configured to
is for forming an image on the photocathode 29a of the imaging device 29, and the light beam reflected by the anterior segment 7 is transmitted to the beam splitters 20, 41 and the reflecting mirror 42.
After being reflected by the imaging lens 43, the half mirror 27, and the imaging lens 28, the imaging device 2
An anterior segment image is formed on the photocathode 29a of No.9.

The imaging device 29 is connected to a television monitor 44, and 45 is its display surface. This display surface 4
5, an image formed on a photocathode 29a based on a video signal from an imaging device 29 is displayed as a visible image. In addition, in Figure 1, 4
6 is a measurement target image formed by the imaging optical system 2, and 47 is an anterior segment image formed by the aiming optical system 2.

Here, when the target image 46 displayed on the display surface 45 of the television monitor 44 is in focus on the fundus 8, as shown in _FIG. The distance _l2 between the pair of target images 46b is the same. For example, if the measurement target image is focused in front of the fundus 8, the interval _l1 will be smaller than the interval _l2 as shown in FIG. Assuming that the object is in focus, the distance l ₁ will be larger than the distance l ₂ as shown in FIG.

When objectively measuring refractive power, the index plate 11 is moved so that the distances l ₁ and l ₂ between the measurement target images match, and the eye refractive power is determined by the amount of movement of the index plate 11 at this time. That will happen. In this case, the moving lens 25 is driven integrally with the index plate 11 while maintaining a conjugate relationship.

Next, the measurement circuit shown in FIG. 7 will be explained.

A portion of the video signal from the imaging device 29 described above is input to the television monitor 44 to display an image of the anterior segment of the eye, and the other portion is input to the video signal extraction circuit based on a command signal from the extraction command circuit 51. 52, the image signal is extracted as a video signal regarding the measurement target image. The extracted video signal is subjected to waveform processing in a rectangular wave generation circuit 53 to convert it into a predetermined rectangular wave, and the obtained rectangular wave is processed by a video signal level determiner 54 to determine its luminance. While the level, that is, the light intensity level of the measurement target image 46 is detected, the signal interval, that is, the interval of the measurement target image 46 is detected by the target image position detection circuit 55.

Here, signal processing of the output signals from the video signal level determiner 54 and the target image position detection circuit 55, or each signal to be described later, is performed by the CPU 50 of the microcomputer.

The CPU 50 includes an accommodation force measurement start switch 56 operated at the start of accommodation force measurement, and a chart board 3.
3, a drive switch 58 for moving the index plate 11 and the moving lens 25, and an auto measurement start switch 5 for starting auto measurement.
9 respectively. Further, the CPU 50 controls a drive control section 60, which includes a first drive control section 61 for moving the index plate 11 and the movable lens 25 along the optical axis, and an image rotator 18.
A second drive control section 62 for rotationally driving the chart projection system 4 around the optical axis, and a third drive control section 63 for moving the movable lens 34 of the chart projection system 4 along the optical axis. Note that the CPU 50 runs a pre-installed predetermined automatic measurement program 64.
Alternatively, an accommodation force measurement program 65 is executed, and each measurement result is sequentially recorded by a printer 67.

Next, the operation of the eye refractive power measuring apparatus constructed as described above will be explained with reference to the flowchart of FIG. 8.

First, when the CPU 50 starts executing arithmetic processing by turning on the power, etc., step 10 is executed.
When the auto measurement switch 59 is turned on at 0, the CPU 50 starts the auto measurement program 64.
The following measurements are performed accordingly.

First, in the initial setting in step 101, the first drive control section 61 sets the index plate 11 to the 0 day opter position, and the second drive control section 62 sets the image rotator 18 to the ₀₀ position in synchronization with the first drive control section 61. The third drive control section 63 is controlled by
to move the movable lens 34 to the 0 day opter position,
That is, settings are made to move the chart board 33 to each far point position.

In the following step 102, the distances l ₁ and l ₂ between the measurement target images 46 are detected based on the output from the target image position detection circuit 55. This interval l ₁ , l ₂
is detected, the CPU 50 calculates the interval difference l ₁ −l ₂ and adjusts the index until the interval difference l ₁ −l ₂ becomes 0, that is, until the measurement target image 46 is focused on the fundus 8. The plate 11 and the moving lens 25 move together along the optical axis. In conjunction with this movement, the moving lens 34 of the chart projection system 4 moves (step 1).
02 to 105), the eye 6 to be examined is kept in a foggy state at all times. And the interval difference l ₁ −
When l ₂ becomes 0, the position of the moved indicator plate 11 is read (step 106), and the refractive power in the 0° meridian direction is obtained based on this moved position.

Next, the image rotator 18 rotates, for example, 15 times every 6 ₀ (direction of the meridian to be measured) while keeping the position of the index plate 11 fixed, and the interval difference l ₁ - l ₂ corresponding to each rotation position is determined. is read (steps 107-109). Here, the refractive power in the θ direction
D〓 is obtained by calculating the sum of the diopter value corresponding to the stop position of the index plate 11 and the diopter value corresponding to the interval difference L ₁ −l ₂ value. and,
This refractive power D〓 is spherical power A, astigmatic power B,
and the astigmatic axis α have a relationship expressed by the following equation (1).

D〓=A+Bcos(θ−α) …(1) Therefore, based on the refractive power D〓 ₁ to D〓 ₁₅ obtained in each meridian direction (15 meridian directions), the spherical power A and the astigmatic power are determined by the least squares method. B and astigmatism axis α are calculated (steps 110 and 111). Then, these calculation results are displayed or recorded as measured values on the television monitor 44 and printer 67 (steps 112 and 113), and the measurement of the distance refractive power by automatic measurement is completed.

Next, when the adjustment force measurement program 65 is to be executed, the process moves from step 114 to step 115, where it is determined whether or not to execute it. When the accommodation force measurement start switch 56 is turned on, the CPU 50 starts the accommodation force measurement program 6.
5, and the following accommodation force measurements are performed according to this program. In addition, in this accommodative force measurement, the chart plate 33 of the chart projection system 4 functions as a visual acuity board for measuring the accommodative force.

In executing this program 65, first,
In step 115, the movable lens 34 and the index plate 11 are initially set at positions corresponding to the distance refractive power obtained by executing the above-mentioned automatic measurement program 65. With this initial setting, the chart board 33 and the index board 11 are placed at approximately the far point position of the eye 6 to be examined, and the position scale at this far point position is read (steps 116 and 117).

In this case, a measurement target image made of invisible light and a chart image made of visible light are projected onto the eye 8 in a superimposed manner, but only the chart image is visible to the subject. Further, at this far point position, the subject can focus on the chart image, and the measurement target image on the display surface 45 of the television monitor 44 at this time is shown at the distance l ₁ , It can be observed that l ₂ almost coincides with each other.

Next, the examiner turns on the drive switch 57 (step 118), and turns on the index plate 11 and the chart plate 3.
3 (which may also be the projection lens 34) are moved integrally in the optical axis direction, that is, in the periapsis direction (steps 119, 120), and the measurement target image 46 is displayed on the display surface 45 as shown in FIG. When they start to split, their movement is stopped (step 121). This time is regarded as the periapsis position and the position scale is read (step 122), the accommodation force is calculated from the difference in the position scale between the periapsis position and the far-point position (step 123), and the result is displayed on the television monitor 44. At the same time, the information is recorded by the printer 67 (steps 124 and 125).

In this example, after measuring the distance refractive power by automatic measurement, the accommodative power is measured without correcting the subject's astigmatism. A cylindrical power conversion lens is inserted into each, and the test subject's astigmatism is corrected using the cylindrical power conversion lens based on the astigmatism power and astigmatism axis obtained by automatic measurement, and then the accommodative power is measured. If configured to perform this, more accurate measurement results can be obtained.

Effects of the Invention As described above, according to the present invention, the accommodative power of the eye to be examined can be measured based on the change in the focus state of the measurement target image accompanying the change in the focus state of the test chart image. Therefore, it becomes possible to objectively measure the accommodation force, and more accurate measurement results can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the optical system of an automatic eye refractive power measuring device according to the present invention, Fig. 2 is a perspective view of an index plate constituting the optical system, and Fig. 3 is a chart plate constituting the optical system. 4 to 6 are schematic diagrams showing various aspects of the imaging state of the measurement target image formed by the optical system, and FIG. 7 is a measurement circuit diagram for driving the device, FIG. 8 is a flowchart for executing the program by the measuring circuit. DESCRIPTION OF SYMBOLS 1... Measurement target image projection system, 4... Chart projection system, 6... Eye to be examined, 29... Imaging device, 33... Chart board, 46... Measurement target image, 50... CPU,
65...Adjustment force measurement program.

Claims (1)

[Scope of Claims] 1. A chart projection system for projecting a test chart image onto the fundus of an eye to be examined using visible light, and a measurement target projection system for projecting a measurement target image onto the fundus of an eye to be examined using invisible light. and an observation system for converting the measurement target image into a visible image for observation, and capable of changing the focus state of the measurement target image at the same time as changing the focus state of the inspection chart image. an accommodative force measuring element configured to An eye refractive power measuring device characterized by comprising: 2. The measurement target image projection system is configured so that the time when the split measurement target image is formed on the fundus of the eye to be examined is the time when the measurement target image is out of focus. The eye refractive power measuring device according to item 1. 3. The chart projection system consists of a chart board for inspection and a projection lens for projecting the light beam from the chart board onto the fundus of the eye to be examined, and at least one of the chart board or the projection lens is moved along the optical axis. 2. The eye refractive power measuring device according to claim 1, wherein the eye refractive power measuring device is configured such that the focusing state of the chart image on the inspection chart board can be changed. 4 The accommodative power measuring device moves the inspection chart plate or projection lens toward the near point from the initial setting position corresponding to the distance refractive power to the position until the measurement target image observed by the observation system is out of focus. 4. The eye refractive power measuring device according to claim 3, further comprising a calculation means for moving the eye toward the subject's eye and calculating the accommodation power of the eye to be examined based on the amount of movement.