JP2002233502A - Contrast chart device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contrast chart device capable of easily obtaining an aberration of an eye to be tested by simultaneously measuring the contrast sensitivity and the diameter of a pupil of the eye to be tested. SOLUTION: This contrast chart device has a contrast index presenting part 100 for presenting a contrast index for contrast sensitivity test in a designated timing, a pupil diameter measuring part 500 for forming an image of an anterior ocular segment 401 of a tested person and measuring the pupil diameter of the anterior ocular segment 401, and a measuring timing forming part 600 for forming the measuring timing of the pupil diameter measuring part 500 according to the above timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contrast chart apparatus suitable for use in a visual acuity test using a contrast chart. More specifically, the present invention relates to a contrast chart device that can simultaneously measure a pupil diameter and a contrast sensitivity, which is suitable for accurately determining the aberration of an eyeball of a subject as in laser ophthalmic surgery.

[0002]

2. Description of the Related Art Recently, ophthalmic surgery in which a cornea or the like is deformed by a laser has been attempted, and in that case, it has become important to accurately measure the aberration of the eye. In such corneal surgery and cataract surgery, contrast sensitivity is measured in addition to the visual acuity measured by a general visual acuity test. For example, in the case of an abnormality of the eye optical system such as a cataract or a refractive error, the contrast sensitivity in a high frequency band first decreases. Therefore, if the contrast sensitivity in the medium to low spatial frequency band, which is not affected by the correction technique such as a general visual acuity test, and is not affected by the correction, should be measured, it can be used for surgery for early cataract. Can be accurately determined.

Here, the general visual acuity test using a standard visual acuity chart tests the visual acuity of a small object having a high contrast ratio. Thus, for example, in a cataract patient, the opacity of the crystalline lens causes light scattering and lowers the contrast of the image at the fundus, but does not affect the shift of the optical focal position of the image. As a result, the image at the fundus is blurred, but may be read as characters by an optometrist who is a cataract patient. Also, when spherical aberration is caused by optical distortion between the cornea and the crystalline lens, the image at the fundus is blurred, but may be read as characters by the examiner.

[0004] On the other hand, in ordinary visual life, there are many conditions under which scattered light is likely to increase, and objects with low contrast are often seen. Therefore, in the measurement of the contrast sensitivity, a sine-wave grid pattern is used in order to measure the visual recognition ability of a figure having no sharp outline and a small difference between a bright place and a dark place. The sinusoidal lattice fringe is a fringe pattern in which the shading changes sinusoidally. The contrast sensitivity measures the minimum contrast required to recognize a stripe pattern at various finenesses (spatial frequencies).

[0005]

As described above, in a general visual acuity test in which the contrast is constant, there is a problem that even a small change in the aberration of the eye has little effect. Therefore, contrast sensitivity measurement is performed in which the measurement is performed while changing the contrast. However, since the diameter of the pupil of the subject's eye greatly affects the aberration of the subject's eye,
A need has arisen to obtain data on the pupil diameter together with the presentation of the target.

However, the conventional contrast chart apparatus has a problem that it merely presents a target whose contrast changes, and cannot measure the diameter of the subject's pupil. An object of the present invention is to solve the above-described problems, and to provide a contrast chart device in which aberrations of an eye to be inspected can be easily obtained by simultaneously measuring contrast sensitivity and a diameter of a pupil of the eye to be inspected. .

[0007]

To achieve the above object, a contrast chart apparatus according to the first aspect of the present invention provides a contrast index for a contrast sensitivity test at a predetermined timing as shown in FIG. A contrast index presenting unit 100 to be presented; an anterior eye part 4 of the subject
A pupil diameter measurement unit 500 that forms an image No. 01 and measures a pupil diameter of the anterior eye part 401; and a measurement timing formation unit 600 that forms measurement timing of the pupil diameter measurement unit 500 according to the timing. ing. The contrast index is a combination of a general visual acuity test index such as a Landolt ring index, a cinelen (Snellen) character index and a pedestal index, and a spatial frequency characteristic (MTF) such as Gabor stimulation. : Contrast sensitivity index suitable for measurement of Modulation Transfer Function).

In the apparatus configured as described above, the contrast index presenting unit 100 presents a contrast index for a contrast sensitivity test to the anterior eye 401 of the subject at a predetermined timing. The contrast sensitivity is tested by responding to whether the subject has seen the presented contrast index. Measurement timing forming unit 6
00 generates a timing signal for the pupil diameter measurement unit 500 to measure the pupil diameter of the subject based on the timing at which the contrast index presentation unit 100 presents the contrast index to the anterior eye 401 of the subject. Therefore, the contrast sensitivity and the pupil diameter of the subject can be measured simultaneously.

Preferably, the contrast index presenting section 10
0 is the first illumination optical system 110 which mainly forms an index
And a second illumination optical system 210 that mainly forms a background, and further includes a first illumination optical system 110 and a second illumination optical system 2.
It is configured that the light fluxes from the light source 10 are combined, pass through the first mirror 302 for turning back, are reflected by the second mirror 303, are then reflected by the first mirror 302 again, and are directed toward the eye 400 to be inspected. The contrast between the index and the background can be easily adjusted.

[0010] Preferably, the first illumination optical system 110 includes:
If the index having different sizes is selectively inserted into the optical path, the contrast sensitivity of the subject can be measured quickly. In addition, when the second illumination optical system 210 is configured to form light fluxes of substantially uniform brightness different in brightness, it is easy to combine a background having a contrast required for an index. it can.

Further, the pupil diameter measuring unit 500 is configured to form an image of the anterior segment 401 of the subject via the first mirror 302 and measure the pupil diameter of the anterior segment 401. Pupil diameter measuring section 500 and contrast index presenting section 10
The optical system can be shared by 0 and the structure is simplified. The pupil diameter measuring unit 500 may be configured to measure the pupil diameter of the subject at the presentation timing sent from the measurement timing forming unit 600 to the contrast index presenting unit 100 or at the timing when the subject responds. .

Further, if at least the measured pupil diameter of the subject and the contrast index presented at the time of measuring the pupil diameter can be output to an apparatus for measuring the shape of the eyeball, the pupil diameter of the eye to be examined In consideration of the above, the aberration of the subject's eye can be measured. Therefore, for example, in an ophthalmic surgery in which a cornea or the like is deformed by a laser, a portion of the cornea to be scanned by the laser can be easily determined.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description will be omitted. FIG. 1 shows the first embodiment of the present invention.
FIG. 1 is a configuration diagram illustrating an embodiment of the present invention, in which an optical system and a control system are shown in the same drawing. In the figure, the contrast index presenting unit 100 includes a first illumination optical system 110, a test index display control unit 120, a second illumination optical system 210, and a pedestal index display control unit 220.

The first illumination optical system 110 mainly forms a test index, and includes a light source 101, a condenser lens 102, an index exchange rotating motor 103, and an index plate 10.
4, an ND filter 105, a magnification correction lens 106, and a diffusion plate 107. Condenser lens 102
Converts the light emitted from the light source 101 into a parallel light flux. The index plate 104 includes various contrast indices, such as a general visual acuity test index such as a Landolt ring optotype and a Cinelen character optotype, and a contrast sensitivity test index suitable for measuring spatial frequency characteristics such as Gabor stimulation. The characters are printed in a predetermined size. In the case of a general visual acuity test index, a visual acuity of 1 minute is defined as a visual acuity of 1.0, a visual acuity of 0.1,
.., Various characters and patterns for 2.0 are drawn with a thickness corresponding to a visual angle corresponding to visual acuity. In the contrast sensitivity index, the spatial frequency is 1.5, 3, 6, 1 at a viewing distance of 3 m.
A striped pattern of 2, 18 [cycles / deg] is drawn.

ND (Neutral Density) filter 105
Is a filter that changes only the amount of light such as 60% transmission or 40% transmission, and does not perform polarization or the like. Magnification correction lens 106
Has a focal length such as infinity (0 diopter) or 5 meters (0.2 diopter), and adjusts the magnification correction lens 106 to be replaced to present a test index to the subject. The diffusion plate 107 diffuses the light emitted from the condenser lens 102 to make the light amount distribution uniform.

The second illumination optical system 210 mainly forms a background such as a pedestal index.
Condenser lens 202, index exchange rotary motor 20
3, an index plate 204, an ND filter 205, a magnification correction lens 206, and a diffusion plate 207. The second illumination optical system 210 is composed of substantially the same optical components as the first illumination optical system 110, but differs in that the index printed on the index plate 204 is the background. In the case of a general visual acuity test index, since the contrast of the contrast index drawn on the index plate 104 is 100%, the index plate 204
Background is 0%, 10%, 20%, ..., 90
Various contrasts such as% are prepared. In the contrast sensitivity index, since a test index having a predetermined spatial frequency and a predetermined contrast is printed, the printing is performed so that the brightness of the background is adjusted to be substantially the same between different test indexes. ing.

The test index sent from the first illumination optical system 110 and the pedestal index sent from the second illumination optical system 210 are superimposed on the same optical path by a mirror 301,
After passing through the spectral mirror 302 as the first mirror, the second
The light is reflected by the concave mirror 303 serving as a mirror, is again reflected by the spectral mirror 302, and is sent to the anterior segment 401 of the subject. The mirror 301 may be, for example, a half mirror, or the ratio between the transmittance and the reflectance may be determined according to the amount of light required by the light sources 101 and 201. By appropriately setting the ratio between the transmittance and the reflectance of the mirror 301, the energy efficiency is increased as compared with the case where the light is constantly attenuated by the ND filters 105 and 205. In addition, the subject's eye 4
00 is the anterior ocular segment 40 such as the cornea, as is anatomically known.
1 and a crystalline lens 402.

The test index display control section 120 drives the index exchange rotary motor 103 to stop the index plate 104 at an appropriate position, and controls the test subject to present an appropriate test index to the subject. Pedestal index display control unit 220
Drives the index exchange rotary motor 203 to operate the index plate 20.
4 is stopped at an appropriate position, and control is performed so that a pedestal index of contrast or brightness corresponding to the test index can be presented to the subject.

The pupil diameter measuring section 500 includes a light receiving element 501, a light receiving camera lens system 503, and a pupil diameter measuring operation section 520. Since the optical system related to the index uses a visible wavelength, the pupil diameter measurement unit 500 may use near-infrared light, or may use visible light having a wavelength different from the test index. The light receiving element 501 is, for example, a charge-coupled device (CCD: Charge
An element that can receive a two-dimensional image such as a d-Coupled Device is used. The light receiving camera lens system 503 includes the light receiving element 5
The magnification is adjusted so that an image of the pupil can be projected at an optimum magnification on 01. The image of the pupil included in the image of the anterior eye part 401 of the subject received by the light receiving element 501 may be both eyes and one eye. The pupil diameter measurement calculation unit 520 performs image processing and image recognition on the image of the anterior eye part 401 received by the light receiving element 501, and outputs a pupil diameter in real time.

The central processing unit 600 as the measurement timing forming unit uses the contrast index presenting unit 100 to present the contrast index to the anterior segment 401 of the subject or the timing at which the subject responds. , A timing signal for measuring the pupil diameter of the subject by the pupil diameter measurement unit 500 is generated. Further, the central processing unit 600
Has a function of combining and processing the contrast and visual acuity information presented by the contrast index presenting unit 100 and the pupil diameter information of the subject by the pupil diameter measuring unit 500.

FIG. 2 is an explanatory view of contrast using a test index for a general visual acuity test.
%, (B) shows a contrast of 60%, and (C) shows a contrast of 20%. The pedestal indicator is sent from the second illumination optics 210, one simple typical being a mere 100% transmission, or nothing indicator. On the other hand, various characters such as the characters “to” are printed on the index plate 104 as the test indices, such as 0%, 40%, and 80% as the transmittance of the first illumination optical system 110. The contrast is given as the difference between the transmittance of the pedestal indicator and the transmittance of the test indicator. The test index may be a chart for measuring visual acuity, and typically a Landolt ring or a character is used. The test indices are made of Landolt rings and letters in chrome plating on parallel flat glass. The 100% transmitting portion becomes a Landolt ring or a character figure (foreground) portion, and the ground (background) is 0% transparent or the transmittance of the figure and the ground is reversed. Also, for example, white noise or filtered band-limited noise stimulus may be used as the pedestal index instead of 100% transmission.

The measurement of the contrast sensitivity in the device configured as described above will be described. The operator inputs to the central processing unit 600 the contrast using the test index for general visual acuity test that the user wants to display on the anterior segment 401 of the subject. Then, the central processing unit 600 drives the index exchange rotary motors 103 and 203 to position the indexes 104 and 204 that form the corresponding contrast. Then, the first illumination optical system 110 and the second illumination optical system 210 display various contrast indices according to the input of the operator on the anterior segment 401 of the subject. On the other hand, since the subject responds “visible” or “not visible”, the operator can measure the contrast sensitivity of the subject by sequentially raising and lowering the contrast. At this time, since the central processing unit 600 also measures pupil diameter information by the pupil diameter measuring unit 500, the pupil diameter at the time of measuring the contrast sensitivity can be obtained.

In the first embodiment,
Although the case where the test index is transmitted from the first illumination optical system 110 and the pedestal index is transmitted from the second illumination optical system 210 is shown, the pedestal index is transmitted from the first illumination optical system 110 by exchanging the index plates 104 and 204. , A test index may be sent from the second illumination optical system 210. Also, the configuration in which the contrast between the pedestal index and the test index is changed using the index plate 104 has been described.
And the light amount of the light source 101 and the transmittance (density) of the ND filters 205 and 105 may be changed. Although FIG. 2 shows a case where a single test index is presented as a test index, a plurality of test indices based on a psychophysical experiment technique such as a constant method or an up-down method may be presented. Further, when a composite index is presented as a test index, a conventional JIS visual acuity table or E
By presenting the TDRS visual acuity table as a composite index, there is an effect that a JIS visual acuity table or an ETDRS visual acuity table having various values such as a contrast of 10% or 100% can be easily realized.

FIGS. 3A and 3B are explanatory diagrams of contrast using the contrast sensitivity index. FIG. 3A is a plan view of Gabor stimulation projected on the anterior eye of the subject, and FIG. 3B is a plan view of FIG. 5 shows a contrast chart luminance profile in the BB direction of FIG. The peak interval d of the luminance profile corresponds to the spatial frequency. In the case of contrast is 100%, the luminance amplitude of the test indicator TM ₁₀₀ using the Gabor stimulus is large, the pedestal index PM
The luminance of ₁₀₀ is about the minimum value of the Gabor stimulation of about 0.08. On the other hand, in the case of 50% contrast, since the luminance amplitude of the test indicator TM ₅₀ using the Gabor stimulus is smaller than the test indicator TM _100, the luminance of a pedestal indicators PM ₅₀ is the minimum value of about 0.28 of Gabor stimulus It has become.

That is, in the plan view of the Gabor stimulus, the luminance amplitude of the test index differs according to the contrast. Therefore, a pedestal index having a transmittance corresponding to the luminance amplitude of the Gabor stimulus is selected, and the brightness of the contrast sensitivity index is selected. Need to be equal. Therefore, the central processing unit 60
0 drives the index exchange rotary motors 103 and 203 to make the index plates 104 and 204 an appropriate combination. Note that the central processing unit 600 causes the light sources 101, 201
The brightness of the contrast sensitivity index may be made equal by appropriately adjusting the amount of light of the ND filters 105 and 205.

FIG. 4 is a flow chart for explaining a measuring procedure by the vertical method using the contrast sensitivity index of FIG. The up-down method is a kind of psychological measurement method, in which stimulus presentation is a forced selection method in two trials, and the subject answers the one with the Gabor stimulus out of two times. When the measurement of the contrast sensitivity is started (S100), alignment is performed (S102), and the optical system is adjusted so that the Gabor stimulus image is formed on the anterior segment 401 of the subject (S10).
4). When the alignment adjustment is completed, the background is presented to the subject (S106). Next, the first Gabor stimulus is presented (S108), and the pupil diameter is measured (S108).
110), the response of the subject is stored (S112). Subsequently, the background is presented to the subject again (S11).
4), presenting the second Gabor stimulus (S116);
The pupil diameter is measured (S118), and the response of the subject is stored (S120).

Then, the central processing unit 600 judges whether or not the measurement has been completed (S122), and presents the first and second Gabor stimuli to the subject alternately until the measurement is completed.
When the measurement is completed, the central processing unit 600 determines whether or not it is necessary to output to an external device (S124). If the output is specified, the central processing unit 600 outputs the contrast sensitivity and the pupil diameter information by the Gabor stimulation to the relevant external device (S126). ). Then, the measurement of the contrast sensitivity for the subject ends (S128).

FIG. 5 is an explanatory view of a stimulus presenting pattern used in the up and down method of FIG. 4, wherein (A) shows a stimulus presenting pattern 1 and (B)
Represents the stimulus presentation pattern 2. In both of the stimulus presentation patterns 1 and 2, a beep sounds to notify the subject of the start of the stimulus at 0 seconds, the first stimulus from 1 to 2 seconds is the first stimulus, and the 1 second from 4 to 5 seconds is the second stimulus. It has been a stimulus. In the section from 0 to 1 second, 2 to 4 seconds, 5 to 6 seconds,
The background is presented to the subject. The stimulus presentation pattern 1 presents a Gabor stimulus as the first stimulus and does not present a Gabor stimulus as the second stimulus. The stimulus presentation pattern 2 does not present a Gabor stimulus as the first stimulus, but presents a Gabor stimulus as the second stimulus. The time change of the Gabor stimulus is completed in approximately one second in the form of a Gaussian curve, and the relative stimulus contrast smoothly changes from 0.1 to 1.0 to 0.1 in this one second.

FIG. 6 is a diagram showing an example of the change in contrast by the up-down method in FIG. 4, in which the vertical axis represents the contrast and the horizontal axis represents the number of stimulations. 100% contrast (1)
, The contrast of the stimulus is reduced in steps of 0.1 in logarithmic steps each time the subject answers correctly, while the contrast of the stimulus is increased by 4 steps when the subject answers incorrectly. The measurement ends when, for example, nine incorrect answers occur. In this case, the contrast sensitivity of the subject is, for example, an average value of nine times the contrast sensitivity that is incorrect,
For example, it is 0.06 (= 10 ^-1.2 ).

Further, the results obtained by the contrast measurement by the up and down method are summarized in about five levels of the contrast level, and then the average of the contrast threshold value s ₀ and the variance σ are determined by probit analysis, which is one of the statistical analysis methods. And can be asked. If the spatial frequency characteristic MTF of the optical system is known from a wavefront sensor or the like, the spatial frequency characteristic MTF of the optic nerve system can be calculated by the following equation.

(Equation 1)

Here, M _lat is the spatial frequency characteristic MTF of the optic _nervous system to be obtained, and M _opt is the spatial frequency characteristic M of the optical system.
TF, m _n is the contrast of the noise of the optic nerve system, the m _t stimulus _{contrast, k (= s 0 / σ} ) is calculated by dividing a distributed sigma mean value s ₀ of contrast threshold.

FIG. 7 is a configuration diagram for explaining a second embodiment of the present invention. The device of FIG. 7 has a configuration in which a wavefront sensor 700 and an eyeball laser operation device 800 are added to the device of FIG. The wavefront sensor 700 includes the anterior segment 4 of the subject.
The spherical shape of No. 01 is measured, and the deviation of the cornea and the lens constituting the eyeball from the spherical body is measured. When the eyeball laser surgery device 800 deforms the cornea or the like with a laser,
In addition to planning the laser irradiation position on the eyeball surface, the ophthalmologist irradiates the laser along the planned laser irradiation position. The central processing unit 600 is connected to a wavefront sensor 700 as an external device.

In the device configured as described above, the central processing unit 600 provides the wavefront sensor 700 with the measured pupil diameter. The wavefront sensor 700 uses the wavefront measurement data and the pupil diameter measurement together to obtain a point image intensity distribution PS.
F (Point Spread Function) and spatial frequency characteristic MTF are calculated. On the other hand, the point image intensity distribution PSF and the spatial frequency characteristic MTF calculated by the wavefront sensor 700 are sent to the central processing unit 600. The central processing unit 600 stores data such as the measured spatial frequency characteristic MTF and the wavefront sensor 70
Compare with the data such as the spatial frequency characteristic MTF calculated at 0.

In the above embodiment, the case where the contrast sensitivity is measured for each eye of the subject has been described. However, when measuring both eyes of the subject simultaneously, the subject wears polarized glasses. By installing it, a full-fledged stereo test becomes possible.

[0035]

As described above, according to the contrast chart apparatus of the present invention, the contrast index presenting section for presenting the contrast index for the contrast sensitivity test at a predetermined timing, and the image of the anterior eye of the subject And a pupil diameter measurement unit that measures the pupil diameter of the anterior segment, and a measurement timing formation unit that forms the measurement timing of the pupil diameter measurement unit according to the timing. The sensitivity and the pupil diameter of the subject can be measured simultaneously.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of contrast using a general visual acuity test test index.

FIG. 3 is an explanatory diagram of contrast using an index for contrast sensitivity.

FIG. 4 is a flowchart illustrating a measurement procedure by an up-down method using the contrast sensitivity index of FIG. 3;

FIG. 5 is an explanatory diagram of a stimulus presenting pattern used in the up-down method of FIG. 4;

FIG. 6 is a diagram showing an example of a contrast change by the up-down method in FIG.

FIG. 7 is a configuration diagram illustrating a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 contrast index presenting unit 110 first illumination optical system 120 test index display control unit 210 second illumination optical system 220 pedestal index display control unit 301, 302, 303 mirror 400 eye to be examined 500 pupil diameter measuring unit 600 measurement timing forming unit

Claims (7)

[Claims] 1. A contrast index presenting section for presenting a contrast index for a contrast sensitivity test at a predetermined timing; and a pupil for forming an image of a subject's anterior eye and measuring a pupil diameter of the anterior eye. A contrast measuring device comprising: a diameter measuring unit; and a measuring timing forming unit that forms a measuring timing of the pupil diameter measuring unit according to the timing. 2. The contrast index presenting section includes a first illumination optical system mainly forming an index, and a second illumination optical system mainly forming a background; the first illumination optical system and the second illumination. The light beam from the optical system is combined, passes through a first mirror for turning back, is reflected by a second mirror, is reflected by the first mirror again, and is directed to an eye to be inspected; 2. The contrast chart device according to 1. 3. The contrast chart device according to claim 2, wherein the first illumination optical system is configured such that indices having different sizes are selectively inserted into an optical path. 4. The contrast chart device according to claim 2, wherein the second illumination optical system is configured to form light beams having substantially uniform brightness different in brightness. 5. The pupil diameter measurement unit is configured to form an image of a subject's anterior eye via the first mirror and measure a pupil diameter of the anterior eye; The contrast chart device according to claim 2. 6. The pupil diameter measurement unit is configured to measure a pupil diameter of the subject at a timing at which the contrast index is presented or at a timing at which the subject responds;
The contrast chart device according to claim 1. 7. At least the measured pupil diameter of the subject and the contrast index presented at the time of the pupil diameter measurement,
It is configured to be able to output to an eyeball shape measuring device;
The contrast chart device according to claim 1.