WO2018003906A1

WO2018003906A1 - Ophthalmic measurement device

Info

Publication number: WO2018003906A1
Application number: PCT/JP2017/023872
Authority: WO
Inventors: 克己薮崎; 泰亮廣野
Original assignee: 興和株式会社
Priority date: 2016-06-30
Filing date: 2017-06-29
Publication date: 2018-01-04
Also published as: JPWO2018003906A1

Abstract

An ophthalmic measurement device 1 is provided with: an illumination optical system 2 for irradiating an anterior segment of an eye being examined E with a sheet light; an image acquiring unit 3 for acquiring, as a two-dimensional image, a scattered light generated at the anterior segment of the eye being examined E by the sheet light emitted from the illumination optical system 2; and an image processing unit 4 for calculating information pertaining to the intensity of the scattered light on the basis of the two-dimensional image acquired by the image acquiring unit 3.

Description

Ophthalmic measuring device

The present invention relates to an ophthalmic measurement apparatus that irradiates light to an eyeball and measures turbidity generated in anterior aqueous humor and scattered light from infiltrated cells.

It is known that infectious diseases such as uveitis cause infiltration of inflammatory proteins, their condensates, and inflammatory cells in the anterior aqueous humor, causing the anterior aqueous humor to become cloudy. Diagnosis such as uveitis is made by measuring. In recent years, many operations have been carried out to remove the lens that has become cloudy due to cataracts and replace it with an intraocular lens (IOL). Measuring the turbidity of aqueous humor is helpful. Furthermore, it is possible to diagnose the type and state of inflammation by distinguishing and measuring inflammatory proteins and infiltrated cells.

In order to measure the turbidity of anterior aqueous humor, a light scattering phenomenon is usually used. Proteins contained in anterior aqueous humor, condensates thereof, and inflammatory cells have a refractive index different from that of the anterior aqueous humor itself, and thus act as light scatterers. Therefore, when the concentrations of inflammatory proteins, condensates thereof, and inflammatory cells in the anterior aqueous humor increase, they can be regarded as scattered light with respect to the light source irradiated into the eyeball. Since the generated scattered light is weak, as a method for measuring the scattered light, for example, as disclosed in Patent Document 1, an energy efficient laser beam is used as a light source, and the scattered light is photomultiplied. In many cases, a signal amplifier such as a tube is detected by an internal sensor. In Patent Document 1, a laser beam is scanned during alignment of a measurement site, a cross-sectional image of the anterior segment irradiated by the scanned laser beam is observed through an observation optical system, alignment is performed, and a laser is scanned during actual measurement. The scanning of the scanning means is stopped, and the laser beam is positioned in a predetermined direction to perform measurement.

When the eyeball is irradiated with light, the characteristics of the scattered light generated by the measurement object are different. That is, proteins and their condensates that have a particle size smaller than the wavelength of irradiation are regarded as scattered light (flares) in the background as Rayleigh scattering. Also, since the amount contained is large and the intensity of scattered light is very small, it is difficult to measure the scattered light from individual particles, and it is detected in the form of the sum of scattered light generated from countless particles. . On the other hand, inflammatory cells that have infiltrated large condensate or anterior aqueous humor generate scattered light as Mie scattering. Here, since the number is extremely small compared to the Rayleigh scatterer and the intensity of the scattered light is large, the scattered light (cell) of each particle is detected as the peak of the detection signal.

In order to measure flare and cell simultaneously using laser light, a conventionally focused laser light is scanned uniaxially to create a sheet light-like plane, and the flare height from the baseline due to scattered light in that area, and its This is achieved by measuring the number of cell-derived peaks measured in the area. A device that can be measured by such a method is called a flare cell meter.

JP-A-9-182725

However, in such a method, the area to be measured becomes smaller due to restrictions such as the scanning speed of the laser beam, the sensitivity of the light receiving element, and the feasible irradiation time, so the number of cells obtained is statistical. In particular, there was a question of whether the correct values for the entire anterior aqueous humor were shown. In addition, since scattered light information obtained by sensors such as photomultiplier tubes is one-dimensional, only a small number of data point sequences can be obtained, and flare and cells are correctly separated from such a small number of data point sequences. It was difficult to perform appropriate analysis.

Furthermore, the discovery of infection in the above-mentioned intraocular lens replacement surgery should be performed not in the vicinity of the corneal side of the anterior aqueous humor, but in a relatively deep state such as the surgical site where inflammation is assumed, that is, the vicinity of the posterior capsule. In the current flare cell meter, correct flare cannot be measured unless the plane that can be scanned with the laser is at the focal position, and the peak of the detection signal from the cell is blurred at other than the focal position, etc. In addition, there was no method other than irradiating a laser beam to the vicinity of the surface layer of the anterior chamber and obtaining side scatter in a direction perpendicular to the laser beam, and as a result, the deep state could not be seen.

The present invention has been made in view of the above points, and when the anterior segment of the eye to be examined is irradiated with light, it is possible to obtain scattered light information in a wider area than before, and the obtained scattering An object of the present invention is to provide an ophthalmologic measurement apparatus capable of easily separating and evaluating a flare and a cell from optical information.

In order to achieve the above object, the present invention provides an illumination light beam irradiated to the anterior segment of the subject's eye with a long and narrow cross section (for example, a rectangular shape, a rectangular shape with rounded corners, and a short diameter). An illumination optical system that emits light (hereinafter referred to as sheet light) that is considerably shorter than the major axis), and scattered light generated in the anterior segment of the subject's eye by the sheet light irradiated by the illumination optical system. Provided is an ophthalmologic measurement apparatus comprising an image acquisition unit that receives light and acquires it as a two-dimensional image, and an image processing unit that calculates information on the intensity of the scattered light based on the two-dimensional image acquired by the image acquisition unit. (Invention 1)

According to the above invention (Invention 1), the sheet light applied to the anterior eye part hits the scatterer in the anterior aqueous humor and is scattered and received as a two-dimensional image by the image acquisition unit. Information on scattered light in a wide planar area can be recorded at once, and information on the intensity of scattered light is calculated based on the acquired two-dimensional image, and flare and cells are separated from the spatial distribution of scattered light. Can be measured.

In the above invention (Invention 1), it is preferable that the image acquisition unit is constituted by an area sensor or a combination of a line sensor and a scanning mechanism (Invention 2).

According to the above invention (Invention 2), it is possible to easily obtain scattered light in a two-dimensional space by receiving light with an area sensor or with a line sensor via a scanning mechanism. It is possible to easily separate flare and scattered light from the cell, which is difficult only by obtaining typical scattered light information. In addition, the number of scattered light points to be analyzed is overwhelmingly larger than in the conventional method, so it is easy to smooth, and it is possible to assemble a robust measurement method that is less susceptible to noise. It becomes possible to measure with statistically high accuracy.

In the above inventions (1, 2), the sheet light is emitted by a slit opening having an elongated shape (for example, a rectangle, a shape having a rounded corner portion of the rectangle, an ellipse whose minor axis is considerably shorter than the major axis). It is preferably formed (Invention 3).

According to the above invention (Invention 3), it is not necessary to provide a scanning mechanism for scanning the light source in order to irradiate the sheet light, and the apparatus configuration can be simplified.

In the above inventions (1 to 3), the illumination optical system includes a wavelength switching mechanism for switching the wavelength of the sheet light to be irradiated, and the position for irradiating the sheet light and the position for acquiring the scattered light are determined. It is preferable to irradiate the first wavelength sheet light during the alignment operation for aligning the ophthalmic measuring apparatus and the eye to be examined, and to irradiate the second wavelength sheet light during the scattered light measurement (Invention 4). Moreover, in the said invention (invention 4), it is preferable that said 1st wavelength is a wavelength of 550 nm or more, and said 2nd wavelength is a wavelength of less than 550 nm (invention 5).

Since the scattered light to be measured, particularly flare, is measured for the scattered light of small particles in the Rayleigh scattering region, light scattering can be more efficiently generated by irradiating the sheet light with a short wavelength. On the other hand, at the time of the alignment work for determining the optimum observation region, it is better to irradiate the sheet light having a long wavelength instead of the short wavelength because of a light hazard. According to the said invention (invention 4 and 5), since the wavelength of the sheet | seat light to irradiate can be switched easily as needed, it is possible to construct an illumination optical system with good scattering efficiency while considering light hazard. It becomes possible.

In the above inventions (Inventions 1 to 5), the angle formed by the optical axis of the illumination optical system and the optical axis of the light receiving optical system of the image acquisition unit is preferably in the range of 25 to 90 degrees (Invention 6). .

Conventionally, the scattered light was measured by irradiating the vicinity of the surface layer of the anterior eye part with laser light and obtaining side scatter in a direction perpendicular to the laser light. In the present invention, the sheet light is measured by the illumination optical system. Can be obtained as a two-dimensional image of all the scattered light in the range through which the sheet light passes, so that backscattering can also be obtained by injecting light from the vicinity of the center of the cornea to the pupil side. Is possible. As in the above invention (Invention 6), by making the angle formed by the optical axis of the illumination optical system and the optical axis of the light receiving optical system of the image acquisition unit to be 90 degrees or less, scattering in the range from side scattering to back scattering A two-dimensional image of light can be acquired. By setting the angle to 25 degrees or more, the image acquisition unit does not interfere with the incident axis (illumination optical axis) of the sheet light. Thus, if a two-dimensional image including scattered light information by backscattering is acquired, information on the flare in the deep part of the anterior eye part can be easily obtained.

According to the ophthalmologic measurement apparatus of the present invention, when the anterior eye part is irradiated with light, it is possible to obtain scattered light information in a wider area than before, and from the obtained scattered light information, flare and cells can be easily obtained. It becomes possible to evaluate separately.

1 is a schematic diagram illustrating a configuration of an ophthalmologic measurement apparatus according to an embodiment of the present invention. It is a schematic diagram explaining a mode that sheet | seat light is irradiated to a to-be-tested eye by the illumination optical system of the ophthalmic measurement apparatus which concerns on the same embodiment, and a mode that the image acquisition part of the ophthalmology measurement apparatus receives the scattered light. It is a block diagram which shows the structure of the image process part of the ophthalmic measurement apparatus which concerns on the same embodiment. (A) is explanatory drawing which shows the range which can measure scattered light with the conventional laser beam irradiation type flare cell meter, (b) is explanatory drawing which shows the range which the ophthalmic measuring apparatus based on the embodiment can measure scattered light It is. The explanatory view which shows the two-dimensional image of the scattered light acquired by the ophthalmologic measurement apparatus according to the embodiment, and the histogram generated by quantifying the intensity of the scattered light of a part of the two-dimensional image (the range of the broken line part) is there. It is a schematic diagram for demonstrating that the depth which can be measured changes when the angle which measures scattered light is changed in the measurement of the flare in the ophthalmic measurement apparatus which concerns on the embodiment. (A) shows the case where only side scattering is observed, and (b) shows the case where it can be observed including backscattering. It is a graph which shows the result of having compared the intensity | strength of the scattered light obtained when the ophthalmic measuring apparatus which concerns on the same embodiment irradiates the sheet light of a different wavelength. It is a graph which shows the measurement result of the scattered light by the ophthalmic measurement apparatus which concerns on the same embodiment, and the measurement result by the conventional laser beam irradiation type flare cell meter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the ophthalmologic measurement apparatus 1 according to the present embodiment includes an illumination optical system 2 that irradiates sheet light to the anterior chamber of the eye E, and sheet light that is irradiated by the illumination optical system 2. The image acquisition unit 3 that receives the scattered light generated in the anterior chamber of the eye E to be acquired and acquires it as a two-dimensional image, and information on the intensity of the scattered light based on the two-dimensional image acquired by the image acquisition unit 3 It is comprised from the image processing part 4 which calculates. The angle θ is an angle formed by the illumination optical axis L1 of the illumination optical system 2 and the light reception optical axis L2 of the image acquisition unit 3.

The illumination optical system 2 in the present embodiment includes an LED light source 21, a condensing lens 22, a slit 23, a collimator lens 24, and a reflection mirror 25, as shown in FIG. The light emitted from the LED light source 21 is condensed by the condenser lens 22 onto the slit opening of the slit 23, and the light that has passed through the slit 23 becomes a parallel light beam by the collimator lens 24, and the direction is changed by the reflection mirror 25 and the eye E is examined. The anterior chamber of the eye is irradiated as sheet light.

The sheet light irradiated from the illumination optical system 2 is irradiated from the cornea of the eye E to the anterior aqueous humor with a predetermined width and height. As means for irradiating the eye to be inspected with sheet light as illumination light, a configuration of the illumination optical system 2 of the present embodiment, a configuration in which a laser light source and a scanning mechanism are combined, and the like are considered in the present invention. Various configurations can be employed without being limited to the configuration. For example, the light source used in the illumination optical system 2 is not limited to a laser light source or an LED light source, but a white light source such as a halogen lamp or a xenon lamp, or a bandpass for extracting a specific wavelength region from these light sources. A combination of filters may be used. Further, the means for converting the light from the light source of the illumination optical system into sheet light can be configured by selecting and combining one or more from a cylindrical lens, a Powell lens, a slit, and the like. Alternatively, the illumination light can be converted into sheet light by scanning light from a light source with a galvano scanner or a polygon mirror.

The LED light source 21 of the illumination optical system 2 is configured by combining at least two types of LEDs (not shown) having different wavelengths so that the wavelength of the sheet light to be irradiated can be switched. Of the two types of LEDs, one is an LED with a wavelength of 550 nm or more (wavelength is 550 nm or larger), and the other is an LED with a wavelength of less than 550 nm (wavelength smaller than 550 nm). By applying a voltage, the wavelength of the sheet light to be irradiated can be switched as necessary. For example, a red LED having a low light hazard can be used as an LED having a wavelength of less than 550 nm, and a short wavelength blue LED capable of efficiently obtaining scattered light can be used as an LED having a wavelength of 550 nm or more.

When an inflammatory reaction occurs in the eyeball, the concentrations of albumin and globulin in the anterior aqueous humor increase. These are proteins with a particle size of several nanometers to several tens of nanometers, and generate very small scattered light (Rayleigh scattering). Rayleigh scattering reduces the intensity of scattered light in inverse proportion to the fourth power of the wavelength of the light source used, as shown in Equation 1 below.

Here, Ks is the scattered light intensity, n is the number of particles, m is the reflection coefficient, d is the particle size, and λ is the wavelength of the incident light. As Equation 1 shows, very short scattered light can be obtained when the wavelength is short, so that the detection sensitivity of the scattered light can be greatly improved by using a short wavelength light source.

However, on the other hand, since light having a short wavelength has a light hazard, the eyeball is aligned while aligning the position where the sheet light is irradiated and the position where the scattered light is acquired and determining the optimum observation area. It is not desirable to continue exposure to short wavelengths. Therefore, alignment adjustment is performed under light on the long wavelength side with little light hazard, and when the alignment adjustment is completed, switch to the light source on the short wavelength side, and switch to the light source on the long wavelength side after shooting, or whichever By turning off the light source, it is possible to construct a measurement system with less light hazard while increasing the sensitivity of scattered light detection.

In this embodiment, as a wavelength switching mechanism for switching the wavelength of the sheet light to be irradiated, a technique of combining at least two types of LEDs having different wavelengths is employed, but the wavelength switching mechanism is not limited to this. For example, a combination of a white light source such as a halogen lamp, a xenon lamp, or a white LED and several band pass filters, or a low pass filter that transmits light in a short wavelength region and a high pass filter that transmits light in a long wavelength region. The wavelength switching mechanism can be realized by combination. Alternatively, a method of irradiating the anterior eye part with white sheet light and dispersing the generated scattered light is also conceivable. Specifically, using a halogen lamp, a xenon lamp, or two or more types of spectral filters that irradiate the anterior ocular segment with white LED light and irradiate the scattered light generated in front of the image sensor. It is a method of spectroscopic. In this case, it can be realized by a method of combining a monochrome camera and a filter switching mechanism, or by using a color camera and acquiring a red component and a blue component of scattered light without a filter switching mechanism. When a plurality of LEDs having different wavelengths are used in combination as in this embodiment, the wavelength of the sheet light can be easily switched by simply applying a voltage to the LED to be lit without requiring mechanical control. There is an advantage that you can.

The image acquisition unit 3 is a camera mechanism that includes at least an imaging lens 31 and an imaging element 32, as shown in FIG. In the present invention, since the scattered light is detected as a plane by detecting the scattered light generated from the anterior aqueous humor where the sheet light has crossed, a CCD (charge coupled device) camera or CMOS (complementary) is used as the imaging device 32. An area sensor such as a conductive metal oxide semiconductor device) camera is used. Alternatively, a two-dimensional image can be obtained by mechanically scanning a CCD or CMOS line sensor.

Note that the amount of light scatterers contained in the anterior aqueous humor is very small, and the obtained scattered light is not so strong. Therefore, if the exposure time for shooting one frame such as a video rate (30 milliseconds) is short. Scattered light cannot be detected. Therefore, the exposure time should be sufficiently extended to detect scattered light, but it must be determined in consideration of the maximum possible exposure time in consideration of light hazards and the time during which the examinee can keep blinking. . For this reason, a range of about 100 milliseconds to 1 second is considered as a realistic exposure time.

The image processing unit 4 calculates information related to the intensity of scattered light based on the two-dimensional image acquired by the image acquisition unit 3, and in this embodiment, as shown in FIG. The data storage unit 42 storing the two-dimensional image acquired by the image acquisition unit 3, the information on the intensity of the scattered light calculated based on the two-dimensional image, and the two-dimensional image described above The display output unit 43 is configured to display information on the image, the intensity of scattered light, and the like. The image acquisition unit 3 is connected to the data storage unit 42, and the two-dimensional image acquired by the image acquisition unit 3 is stored in the data storage unit 42.

Subsequently, a method of measuring turbidity generated in the anterior aqueous humor of the eye to be examined and scattered light (flares and cells) due to infiltrated cells using the ophthalmic measurement apparatus 1 according to this embodiment will be described. In a conventional flare meter or flare cell meter, as shown in FIG. 4A, a laser beam as a point light source is scanned in one direction near the cornea in the anterior chamber, and the laser beam inside the anterior chamber is The intensity of scattered light at each passing point is detected by a photomultiplier tube which is a point light receiving element disposed in a portion perpendicular to the incident angle. On the other hand, in the ophthalmologic measurement apparatus 1 according to the present invention, as shown in FIG. 4 (b), sheet light is generated by the illumination optical system 2, and this is irradiated to the anterior chamber of the eye to be examined and scattered in a sheet shape. Light is acquired as a two-dimensional image by detecting light with the image sensor 42 which is an area sensor in the image acquisition unit 3. That is, in the conventional laser light irradiation type flare cell meter, the scattered light is obtained as one-dimensional data, whereas the ophthalmic measuring apparatus 1 according to the present invention can measure the scattered light in a wide plane area in two dimensions. Become. The two-dimensional image obtained in this way is shown in FIG.

In addition, since the conventional laser light irradiation type flare cell meter can only obtain a linear scattered light signal (one-dimensional data), it is difficult to correctly separate the flare and the cell from a small number of data point sequences. In the ophthalmologic measurement apparatus 1 according to the present invention, since scattered light is obtained as a planar image, flare and cells can be easily separated. In addition, since there are many data points, it is easy to remove noise and stable flare measurement can be expected.

In order to obtain the two-dimensional image shown in FIG. 5, a sheet light is irradiated to the subject's eye by the illumination optical system 2 of the ophthalmic measuring apparatus 1, and a slit (sheet light of the sheet light) is formed at the cornea portion of the anterior chamber of the eye to be examined. It was focused so that the shape of the entrance was a rectangle with a width of 0.2 mm and a height of 2 mm. Further, as the image acquisition unit 3 of the ophthalmic measurement apparatus 1, a high-sensitivity CMOS monochrome camera DMK23UX174 (installed by Sony IMX174 as the image pickup device 32) manufactured by The Imaging Source (Bremen, Germany) is used, and software attached to the camera Software for controlling and photographing the camera was created using a development kit (SDK), and gain and exposure time were adjusted to capture weak scattered light. From the high-sensitivity CMOS monochrome camera, 8-bit or 12-bit gray-scale luminance data can be obtained.

The acquired two-dimensional image is stored in the data storage unit 42 of the image processing unit 4, and the CPU 41 of the image processing unit 4 calculates information on the intensity of scattered light based on the two-dimensional image. Specifically, the CPU 41 sets an observation region R (region surrounded by a broken line in FIG. 5) on the two-dimensional image, and the luminance data of each pixel in the observation region R is used on the right side of FIG. A histogram of scattered light luminance as shown is created. The observation region R includes a region where the incident sheet light crosses (signal region) and an upper and lower region (background region) sandwiching the region, and the difference between the luminance of the signal region and the luminance of the background region is calculated as the true scattered light intensity. can do. That is, the flare value can be calculated by calculating the difference between the luminance at the center of the histogram and the luminance at the lower portion (baseline) of both sleeves. Cell detection is performed by smoothing the true scattered light intensity obtained using a moving average, calculating an average value using neighboring pixels, and using a median value obtained from neighboring pixels. Is subtracted from the true scattered light intensity image, only the flare disappears and the peak remains. This is measured as a cell. The obtained two-dimensional image, luminance data, histogram, flare value, number of cells, etc. are all stored in the data storage unit 42 and displayed on the display output unit 43 as necessary.

In the present embodiment, the angle θ formed by the optical axis L1 of the illumination optical system 2 and the optical axis L2 of the light receiving optical system of the image acquisition unit 3 can be freely set within a range where the axes do not interfere with each other. The angle θ is preferably set in the range of 25 to 90 degrees in that a two-dimensional image of scattered light in the backscattering range can be acquired. By setting the angle θ to 90 degrees or less, it is possible to obtain a two-dimensional image of scattered light in the range from side scattering to back scattering, and by setting the angle θ to 25 degrees or more, the incident axis ( The image acquisition unit 3 does not interfere with the illumination optical axis L1). The mechanism by which the ophthalmic measuring apparatus 1 acquires a two-dimensional image of scattered light in the range from side scatter to back scatter will be described in detail below.

A conventional flare cell meter observes only side scatter as shown in FIG. In this way, if the scattered light is not acquired from the side, all the scattered light generated by the laser light traveling in the direction of the illumination optical axis will be acquired. Correct measurement could not be performed, and it was extremely difficult to adjust the position of the acquired scattered light. Thus, since the conventional flare cell meter had to observe only the side scatter, as a result, only the scattered light on the surface layer of the anterior chamber could be observed.

In the ophthalmic measurement apparatus 1 of the present invention, scattered light spreads over a wide plane area as a two-dimensional image and is captured by the camera mechanism of the image acquisition unit 3, so that the influence of multiple scattering is small, and the display output of the image processing unit 4 Since the two-dimensional image can be displayed on the unit 43, the position of the observation region can be easily determined while viewing the display output unit 43. Therefore, it is not necessary to observe only side scattering, and scattered light including back scattering can be observed. When observation is possible including backscattering, there is an advantage that scattered light in the deep part of the eyeball can be measured as shown in FIG. As a result, it is possible to evaluate deep flares and cells that reach the posterior capsule. For example, it can be expected that flare in the vicinity of the lens after intraocular lens insertion surgery will be measured, leading to early detection of an inflammatory reaction.

Thus, the two-dimensional image obtained by the ophthalmologic measurement apparatus 1 also includes scattered light information of the deep part of the anterior chamber. By designating an arbitrary position in the two-dimensional image, the illumination light of the illumination optical system 2 can be obtained. Since the depth of the designated position can be known from the angle θ formed by the axis L1 and the light receiving optical axis L2 of the image acquisition unit 3 and the distance on the two-dimensional image, the spatial distribution of the scatterer can be evaluated. It becomes possible. Specifically, the angle θ formed by the illumination optical axis L1 of the illumination optical system 2 and the light receiving optical axis L2 of the image acquisition unit 3, the incident coordinates of illumination light on the image P1 (x1, y1), and scattering on the image When arbitrary observation coordinates where light is observed are P2 (x2, y2), the depth (D) of P2 in the region through which the slit light (/ sheet light) passes is the same as that of the camera and the illumination light. Therefore, the following formula 2 is given.

As mentioned above, although the ophthalmologic measuring apparatus based on this invention has been demonstrated based on drawing, this invention is not limited to the said embodiment, A various change implementation is possible. Various parameters in the embodiment may be selected as appropriate. For example, in the selection of the wavelength of illumination light at the time of measurement (second wavelength), turbidity of the anterior aqueous humor due to an inflammatory reaction inside the eyeball is mainly caused by proteins such as albumin and globulin that have infiltrated the anterior aqueous humor, and Since it is a modified condensate, the particle size is very small, and the obtained scattered light depends on Rayleigh scattering, so that the light intensity of Rayleigh scattering is proportional to the sixth power of the particle size, as shown in Equation 1 above. However, since it is inversely proportional to the fourth power of the wavelength of the illumination light, it is considered desirable to use illumination light with a short wavelength as much as possible in order to acquire weak scattered light. FIG. 7 shows the intensity of scattered light when LEDs having various wavelengths are used. The intensity of the scattered light is increased as the wavelength is shorter, and is proportional to the reciprocal of the fourth power of the wavelength (1 / λ ⁴ ), which is applied to the Rayleigh scattering formula. This is also supported by the result that a linear relationship is obtained by taking 1/4 of the wavelength (λ ⁴ ) on the horizontal axis and the scattered light intensity (pixel luminance value) on the vertical axis.

From the results shown in FIG. 7, it is considered preferable to use a blue LED as a light source. Therefore, a model eye containing standard particles of various concentrations is used by using the blue LED light source for the ophthalmic measurement apparatus 1 described above. The relationship between the concentration of particles and the intensity of the scattered light obtained was used. FIG. 8 shows the intensity of scattered light in a dilution series of polystyrene standard particles when the exposure time is 500 milliseconds, and the angle θ formed by the illumination optical axis L1 of the sheet light and the light receiving optical axis L2 of the image acquisition unit 3 is 25 degrees. (Luminance value of pixel) is shown. The scattered light intensity according to the measurement method of the present embodiment showed a linear relationship with a very high correlation with the particle concentration (FIG. 8-A). This result showed a linearity and detection limit equal to or higher than those obtained with a laser flare cell meter (Kowa Co., Ltd. FM-700) which is a conventional measurement method (FIG. 8-B). The scattered light intensity in FIG. 8B is not the luminance value of the pixel but the number of detected photons per millisecond (PhotonPhotocount / ms). From the above results, it was concluded that it is preferable to use a blue LED (short visible light wavelength) in the selection of the wavelength of illumination light (second wavelength) during measurement. In addition, it is desirable to irradiate the human eye with light having a short wavelength in as short a time as possible from the surface of the light hazard. Therefore, at the time of alignment work for aligning the ophthalmic measurement apparatus and the eye to be examined in order to determine the position for irradiating the sheet light and the position for acquiring the scattered light before the measurement, light having a wavelength (first wavelength) of 550 nm or more, More preferably, infrared light is irradiated as sheet light.

DESCRIPTION OF SYMBOLS 1 Ophthalmological measuring apparatus 2 Illumination optical system 21 LED light source 22 Condensing lens 23 Slit 24 Collimator lens 25 Reflection mirror 3 Image acquisition part 31 Imaging lens 32 Imaging element 4 Image processing part 41 CPU
42 Data storage unit 43 Display output unit

Claims

An illumination optical system that radiates sheet light to the anterior segment of the eye to be examined;
An image acquisition unit that receives scattered light generated in the anterior segment of the eye by the sheet light irradiated by the illumination optical system and acquires it as a two-dimensional image;
An ophthalmologic measurement apparatus comprising: an image processing unit that calculates information on the intensity of the scattered light based on the two-dimensional image acquired by the image acquisition unit.
The ophthalmic measurement apparatus according to claim 1, wherein the image acquisition unit is configured by an area sensor or a combination of a line sensor and a scanning mechanism.
3. The ophthalmologic measurement apparatus according to claim 1, wherein the sheet light is formed by a slit opening.
The illumination optical system includes a wavelength switching mechanism that switches the wavelength of the sheet light to be irradiated, and positions the ophthalmic measurement apparatus and the eye to be examined in order to determine a position to irradiate the sheet light and a position to acquire scattered light. The ophthalmologic according to any one of claims 1 to 3, wherein a sheet light having a first wavelength is irradiated during alignment work for alignment, and a sheet light having a second wavelength is irradiated during scattered light measurement. measuring device.
The ophthalmic measurement apparatus according to claim 4, wherein the first wavelength is a wavelength of 550 nm or more, and the second wavelength is a wavelength of less than 550 nm.
The angle formed by the optical axis of the illumination optical system and the optical axis of the light receiving optical system of the image acquisition unit is in the range of 25 to 90 degrees, according to any one of claims 1 to 5. Ophthalmic measuring device.