JP2005118076A - Corneal opacity analysis apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corneal opacity analysis apparatus allowing an operator to grasp the degree of existence of opacity in the direction of thickness of a cornea on the whole cornea at a glance for selecting the kind of operation and determining the depth of resection of the cornea. <P>SOLUTION: The apparatus comprises a reflection intensity discriminating means 10 (S4) for comparing each value of data on the distribution of digital reflection intensity in the direction of thickness of the cornea stored in a data storage device 10b with each threshold value, and discriminating the normal from the abnormal in the result of the comparison, an abnormal number totalizing means 10 (S6) for totalizing the number of parts discriminated as abnormal in the direction of thickness and calculating the number of abnormal parts in the direction of thickness, and density distribution image display means 11 and 10 (S10) for converting the number of abnormal parts in the direction of thickness of each region on the whole scanning range to the expression of density and displaying a density distribution image on the picture corresponding to the state of the cornea as seen from the front. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a corneal turbidity analyzing apparatus capable of analyzing a turbid state generated in a cornea on a surface of an eyeball.

  People who have a marked drop in visual acuity due to corneal opacities can recover their vision by transplanting another person's normal cornea, and so-called eyebanks that register to provide their cornea after death Organization has existed since ancient times.

  However, when the corneal opacity is not significant, particularly when the turbidity region is shallow, visual acuity can be recovered by performing an operation in which the surface portion of the cornea is thinly cut without undergoing corneal transplantation surgery. Therefore, it is important to grasp how deep opacity exists in the thickness direction of the cornea when selecting the type of surgery and determining the excision depth.

  The corneal opacity can be observed to some extent by the naked eye, photography, or the like, by simply shining light on the eyeball from the front. However, this method does not know how much turbidity exists in the thickness direction of the cornea.

  Therefore, conventionally, for example, a corneal cross-sectional image obtained by making slit light incident on the cornea is computer processed, and the degree of turbidity is determined by calculating the light density at each position in the corneal cross-section (for example, Patent Document 1).

  In addition, if an optical coherence tomography (OCT) device that detects a heterodyne beat signal generated from interference of low-coherence light such as radiated light or white light from a light emitting diode (LED) and constructs a tomogram is used, Therefore, it is possible to determine the degree of turbidity from the tomographic image of the cornea.

As for optical coherence tomography, the basic technique is described in Patent Document 2 filed with the Japan Patent Office in November 1990, and applied to aneurysms in Non-Patent Document 1 issued in November 1991. Is described.
JP-A-10-33482 JP-A-4-174345 Dr. Huang et al (MIT), Science Vol.254, P.1178

  However, the device of the invention described in Patent Document 1 is difficult to obtain a clear tomographic image due to large halation caused by irradiating the eyeball with slit light, and the cornea can be obtained from the front side. Since it is only a cut tomogram, it is very difficult to grasp the turbidity of the entire cornea, and it cannot be used for selecting the type of operation or determining the depth of resection.

  Moreover, if optical coherence tomography is used, a tomographic image of the cornea can be obtained with high resolution. However, since only the tomographic image obtained by cutting the cornea from the front side is obtained, the turbidity of the entire cornea is obtained. It is extremely difficult to grasp the state, and it is difficult to use it for selection of the type of operation, determination of the excision depth, and the like.

  Therefore, the present invention can grasp at a glance how much opacity exists in the thickness direction of the cornea, and can be used for selection of the type of surgery, determination of the resection depth of the cornea, and the like. An object is to provide a turbidity analyzer.

  In order to achieve the above object, the corneal turbidity analysis apparatus of the present invention includes an irradiation apparatus that irradiates a living body while scanning a light beam emitted from a low-coherence light source in a predetermined direction, and a refractive index of the living body changes. A photodetector for detecting a change in amplitude of a heterodyne beat signal obtained by superimposing a plurality of reflected lights from a plurality of boundary points in the depth direction and a reference light, and a scanning range obtained from an output signal of the photodetector; An optical coherence tomography device having a data storage device for storing digital reflection intensity distribution data in the depth direction of a living body, and a corneal turbidity analysis device using reflection intensity distribution data by a plurality of scans stored in the data storage device. Focusing means for focusing light irradiation from the low-coherence light source by the irradiation device on the cornea portion of the eyeball surface; A reflection intensity discriminating means for comparing each value of the reflection intensity distribution data in the thickness direction of the cornea stored in the data storage device with a predetermined threshold value and classifying the result into normal and abnormal, and An abnormal number integrating means for calculating the number of abnormal parts for each thickness direction by integrating the number of parts determined to be abnormal by the reflection intensity determining means in the thickness direction, and each part in the entire scanning range obtained by the abnormal part integrating means A density distribution image display means for converting the number of abnormal portions in each thickness direction into a density expression and displaying the density distribution image on a screen corresponding to the state of the cornea viewed from the front is provided.

  The density distribution image display means may display the density distribution in shades of a single color, and the irradiation beam scanning by the irradiation device is performed a plurality of times in a concentric manner, and the density distribution image display means A coordinate conversion means for converting the position where the integrated value of each abnormal part number is obtained into polar coordinate display may be included.

  In addition, a turbidity display means for calculating the total number of abnormal portions in the entire scanning range and displaying the value corresponding to the total number as corneal turbidity directly or with correction corresponding to the scanning condition is added. It is also possible to calculate the ratio of the non-zero abnormal part in the entire scanning range of the cornea from the ratio of the non-zero part and the non-zero part of the abnormal part accumulated by the abnormal part integrating means, and correspond to that ratio A turbid area display means for displaying the value to be displayed as a corneal turbid area directly or with correction corresponding to the scanning condition may be added. By doing so, the state of turbidity of the entire cornea can be grasped quantitatively.

  Further, a surface portion data exclusion means for excluding data in an arbitrary thickness range from the surface of the cornea may be added during the accumulation by the abnormal portion number accumulation means. In this case, the abnormal portion is excluded by the surface portion data exclusion means. It is preferable to provide data exclusion range setting means for arbitrarily setting a range where the number of exclusions is performed. By doing so, it is possible to grasp at a glance the remaining state of turbidity in a state in which the surface portion of the cornea has been cut to an arbitrary thickness.

  According to the present invention, since the cumulative number of abnormal reflection portions for each cornea thickness direction is displayed as a density distribution on the screen corresponding to the state of the cornea as viewed from the front, how much turbidity exists in the cornea thickness direction. The entire cornea can be grasped at a glance, and the surface of the cornea is cut off at an arbitrary thickness by excluding data in an arbitrary thickness range from the cornea surface at the time of image display. The remaining state of corneal opacity in the state can be grasped at a glance, and selection of the type of operation for the cornea and determination of the resection depth can be performed accurately and easily.

  Focusing on the cornea while irradiating a light beam from a low coherence light source by the irradiation device in a predetermined direction, each value of the digital reflection intensity distribution data in the thickness direction of the cornea stored in the data storage device is set to a predetermined value. Compared with the threshold value, the result is classified into normal and abnormal, and the number of areas determined to be abnormal is integrated in the thickness direction to calculate the number of abnormal parts for each thickness direction. Are converted into density expressions in the entire scanning range, and a density distribution image is displayed on a screen corresponding to a state in which the cornea is viewed from the front.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the overall configuration of a corneal turbidity analysis apparatus that can analyze the turbidity state of the cornea 100 using an optical coherence tomography apparatus using a low-coherence light source 1.

  As the low coherence light source 1, for example, a super luminescence diode (SLD) or a light emitting diode (LED) that emits light of a wavelength in the near infrared region is used, and the light emitted from the low coherence light source 1 Are reflected by the galvanometer mirror 3 toward the cornea 100.

  The galvanometer mirror 3 is driven by electromagnetic force as schematically indicated by an arrow A, for example, and can perform high-speed and precise scanning. Reference numeral 31 denotes the drive circuit, and 32 denotes an operation panel for inputting scanning conditions from the outside. However, the scanning means is not limited to the galvanometer mirror 3, and an appropriate scanning means may be arranged and used at an appropriate position.

  The light beam reflected toward the cornea 100 by the galvanometer mirror 3 is partly divided by the beam splitter 4 made of a semi-transparent mirror or the like disposed in the middle thereof and directed to the side movable mirror 5 to straighten the beam splitter 4. The light beam transmitted through is focused on the cornea 100 by the objective lens 6.

  A movable mirror 5 composed of a plane mirror arranged perpendicularly to the light beam split laterally in the beam splitter 4 is moved in the optical axis direction as indicated by an arrow B, and the frequency of the reflected light beam is reduced by the Doppler effect. The reflected light from the movable mirror 5 becomes reference light.

  Then, the reflected light from the cornea 100 portion is reflected laterally by the beam splitter 4, so that the light beam and the reflected light (reference light) from the movable mirror 5 are superimposed on the beam splitter 4, and the converging lens 7. Then, the light enters the photodetector 8 made of a photoelectric converter. The lenses 2, 6, and 7 may be arranged at appropriate positions as necessary, and may not necessarily be provided at the positions shown in FIG.

  In this manner, the photodetector 8 detects a change in the amplitude of the heterodyne beat signal obtained by superimposing the plurality of reflected light from the plurality of boundary points where the refractive index in the depth direction of the cornea 100 changes and the reference light. Is done.

  The output signal from the photodetector 8 is digitized by the analog / digital converter 11 and sent to the computer 10. Reference numerals 10 a and 10 b are a central processing unit (CPU) and a memory (RAM, ROM, etc.) of the computer 10, and reference numerals 11 and 12 are a display and a keyboard connected to the computer 10.

  In the computer 10, the reflection intensity distribution data (digital data) in the depth direction of the cornea 100 obtained from the input signal indicating the change in the amplitude of the heterodyne beat signal is stored in the memory 10b over the entire scanning range.

  In this embodiment, a plurality of light beam scans by the galvanometer mirror 3 on the cornea 100 are performed while changing the radius concentrically. However, it is not always necessary to perform concentric scanning, and linear parallel scanning or the like may be performed.

FIG. 2 shows a scanning example in a state where the cornea 100 is viewed from the front. For the cornea 100 having a radius r of, for example, r = 6 mm, the scanning interval e is set to 0.1 mm, and for example, C from the inside. 60 concentric scans of ₁ , C ₂ , C ₃ , C ₄ ,... C _N (N = 60) are performed.

  Such setting of the scanning condition can be arbitrarily performed on the operation panel 32, and the scanning condition data may be sent to the computer 10 and used for calculation in the computer 10. Alternatively, the scanning conditions may be input from the keyboard 12 of the computer 10 and sent to the drive circuit 31 side.

  FIG. 3 is a developed view of a cross section (scanning cross section) of the cornea 100 irradiated with a low coherence light beam by a single circular scanning. The depth (that is, the thickness of the cornea 100) D is about D = 0.5 mm, and the reflection intensity at each point P in the thickness D direction is detected, and the entire scanning section is reflected as shown in FIG. The intensity distribution data is stored in the memory 10b of the computer 10.

  In FIG. 4, the state of data in one scan is indicated by hatching. However, the memory 10b stores the data in numerical form, and all reflection intensity distribution data obtained by the 60 scans are classified by scan section. Stored.

  5 to 7 are flowcharts of programs executed in the computer 10 to easily analyze the turbidity state of the cornea 100 from the reflection intensity distribution data stored in the memory 10b of the computer 10 as described above. And S indicates a processing step.

  This process is arbitrarily started by inputting a command from the keyboard 12. First, the scanning number counter n is set to n = 1 (S1), and the reflection intensity distribution data of the nth scanning section is input from the memory 10b ( S2) A low-pass filter process for removing high-frequency noise components is performed (S3).

  In the low-pass filter process, a threshold value used for the filter process can be set from the autocorrelation function of the reflection intensity distribution data obtained in advance by the cornea 100 of a healthy person, before and after the low-pass filter process. Fast Fourier transform and inverse Fourier transform may be performed.

  Next, for example, as shown in FIG. 8, the width W and the thickness D of the scanning section are each divided into, for example, 256 to create a data map composed of 256 × 256 spots in two-dimensional coordinates. It is determined whether the reflection intensity is a normal value or an abnormal value from the viewpoint of “presence / absence of corneal opacity”. Then, for example, the abnormality is binarized as “1” and normal is “0” (S4). Note that the number of divisions of the data map may be set as appropriate.

  A threshold value that is a criterion for determining whether the reflection intensity is a normal value or an abnormal value from the viewpoint of “presence / absence of corneal opacity” can be set in advance by collecting a large number of data. In that case, the threshold value may be corrected in accordance with the age of the subject in consideration that the transparency of the cornea decreases with age.

  However, when the subject's cornea 100 has a strong turbidity that affects visual acuity, the intensity is a certain level or more (for example, 70% or more of the strongest intensity, or more than the strongest intensity of the total reflection intensity distribution data, or According to the situation, if a threshold value for determining that a portion of 50% or more, 60% or more, or 80% or more) is abnormal is set, a simple determination can be made.

  In this way, if the normal / abnormal determination result is converted into a binary signal of “0” or “1” for all the data of 256 × 256 points in the scanning section, it is determined to be “abnormal”. The number of spots is accumulated in the thickness direction (S6). Before that, it is determined whether or not the data near the surface of the cornea 100 is to be excluded from the accumulation (S5). Note that the order of S5 and S4 may be interchanged.

  Whether to exclude the data of the portion near the surface of the cornea 100 from the integration is performed by arbitrarily specifying a range of exclusion by input from the keyboard 12, and here, a case where data is not excluded will be described. to continue.

The integration of the number of spots determined to be “abnormal” in the thickness direction is, for example, as illustrated in FIG. 8, the eighth position W ₈ in the 256 portion in the width W direction is the integrated value “5”, 13 th position W ₁₃ is the integrated value "0", so that such 19-th position W ₁₉ is the integrated value "3" is performed for all parts of the 256.

Thus, when 256 total data in the W direction of the integrated value in the depth D direction of the number of abnormal portions in one scanning section as shown in the graph of FIG. 9 are obtained, the scanning number counter n is obtained. S2 to S6 are repeated until N reaches N (N = 60 in this case) (S7, S8). Thereby, as schematically shown in FIG. 10, accumulated value data in the depth D direction of 256 × 60 abnormal parts for all scanning sections of C _{1 to} C _N is obtained.

  Next, in order to restore the position where the integrated value of each abnormal part is obtained to the position in the cornea 100, polar coordinate conversion is performed to return the position where each integrated value is obtained to the original coordinate system at the time of concentric scanning (S9). ). Thereby, as schematically shown in FIG. 11, the integrated value data of the abnormal number is applied to each position corresponding to the state of the cornea 100 viewed from the front.

  Therefore, the integrated value of the abnormal number of each part is converted into a density expression that becomes darker as the value increases, and the density distribution image is displayed on the display 11 (S10). When converting the density expression or displaying the density distribution, a convolution calculation or a well-known interpolation process is performed to display an image with no gap.

  The display is most naturally performed by the density of the black-and-white image. For example, as shown in FIG. 12, a portion having a large integrated value of the abnormal number (that is, a thickness of a portion having an unfavorable level of opacity in the cornea 100) It appears darker and appears lighter as the turbidity thickness decreases.

  In this way, since a density distribution image showing an unfavorable level of turbidity thickness is displayed on the screen corresponding to the state of the cornea 100 viewed from the front, any portion of the cornea 100 can be viewed at a glance. It is possible to grasp at what thickness the turbidity occurs.

  As described above, it is most natural and preferable that the image display of the density distribution is performed in the shade of the black and white image. However, a color other than black and white may be used, or a different color display or the like may be performed for each density. .

  After the image display is completed, a value corresponding to the sum of the integrated values of the number of abnormal parts in the entire scanning range is displayed as a “corneal turbidity” as a number on the display 11 (S11). In the concentric scan, the outer side portion with the larger scanning radius is farther from the adjacent data acquisition position than the inner side scanning portion with the smaller scanning radius, and corresponds to a wider area of the cornea 100. Therefore, it is preferable to convert the sum of the integrated values of the number of abnormal parts into “corneal turbidity” by performing correction that changes the weighting of the value depending on the scanning radius from which the abnormal part data is obtained. Specifically, each data may be multiplied by a scanning number counter n.

  Next, in the entire scanning range, the number of locations where the number of abnormal portions accumulated in the thickness direction is zero is H, and the number of locations where the number of abnormal portions accumulated in the thickness direction is not zero is I / A value corresponding to (H + I) is displayed on the display 11 as “corneal opacity area” (strictly, “corneal opacity area ratio”) (S12). In this case as well, the value weighting may be changed according to the scanning radius from which the abnormal portion data was obtained.

  Returning to S <b> 5 shown in FIG. 5, when an instruction for excluding data of the portion near the surface of the cornea 100 from the integration is input from the keyboard 12, the range of the instruction from the surface of the cornea 100 to where Whether exclusion is designated (for example, exclusion depth J shown in FIGS. 4 and 8) is input (S13), data in the range (exclusion depth J) is excluded, and the thickness direction is the same as in S6 The number of abnormal parts (ie, “1”) is added to (S14), and the process returns to S7.

  By doing in this way, since the density distribution image display of the abnormal part number in the state which cut off the surface part of the cornea 100 only by arbitrary thickness is performed, the residual state of turbidity on the conditions can be grasped at a glance.

  For example, FIG. 13 shows a density distribution image when the surface portion of the cornea 100 is removed by an eighth thickness (J = D / 8), and FIG. 14 shows a quarter thickness (J = D / 4) The density distribution image when removed is illustrated.

  Thus, it is possible to accurately and easily grasp whether or not a transplant operation is necessary for the cornea 100 and how much thickness should be removed when the surface portion is removed.

It is a whole block diagram of the corneal turbidity analysis apparatus of the Example of this invention. It is a schematic diagram which shows the state of the concentric circle scanning in the corneal turbidity analysis apparatus of the Example of this invention. It is a schematic development drawing of the cross section (scanning cross section) of the cornea irradiated with a low coherence light beam by one scanning in the corneal turbidity analysis apparatus of the Example of this invention. It is a schematic development view of the reflection intensity distribution of the scanning section obtained by one scan in the corneal turbidity analyzer of the embodiment of the present invention. It is a flowchart of the program run in a computer in order to perform a corneal turbidity analysis in the corneal turbidity analysis apparatus of the Example of this invention. It is a flowchart of the program run in a computer in order to perform a corneal turbidity analysis in the corneal turbidity analysis apparatus of the Example of this invention. It is a flowchart of the program run in a computer in order to perform a corneal turbidity analysis in the corneal turbidity analysis apparatus of the Example of this invention. It is a schematic development drawing which shows the presence or absence of the abnormal part about all the spots of the scanning cross section obtained by one scan in the corneal turbidity analysis apparatus of the Example of this invention. It is a diagram which shows the state of the integration value of the number of abnormal parts in the scanning cross section obtained by one scan in the corneal opacity analyzer of the Example of this invention. It is a diagram which shows the state of the integration value of the number of abnormal parts in each scanning cross section obtained by full scanning in the corneal turbidity analysis apparatus of the Example of this invention. It is the schematic of the state which applied the integrated value data of the abnormal part number to each position corresponding to the state which looked at the cornea from the front in the cornea opacity analyzer of the Example of this invention. It is a schematic diagram of a concentration distribution image showing the thickness of corneal turbidity obtained by the corneal turbidity analyzer of the example of the present invention. It is the schematic of the density | concentration distribution image which shows the thickness of the turbidity which remain | survives in the case of 1/8 excision of the cornea surface obtained by the corneal turbidity analysis apparatus of the Example of this invention. It is the schematic of the density distribution image which shows the thickness of the turbidity which remain | survives in the case of 1/4 excision of the cornea surface obtained by the corneal turbidity analysis apparatus of the Example of this invention.

Explanation of symbols

1 Low coherence light source 3 Galvanometer mirror (scanning means)
4 Beam splitter 6 Objective lens (focusing means)
8 Photodetector 10 Computer 10b Memory (data storage device)
11 Display (density distribution image display means)
12 Keyboard

Claims (7)

An irradiation device that irradiates a living body while scanning a light beam emitted from a low-coherence light source in a predetermined direction, and a plurality of reflected light and reference light from a plurality of boundary points in the depth direction where the refractive index of the living body changes. And a detector for detecting a change in the amplitude of the heterodyne beat signal obtained by superimposing and a digital reflection intensity distribution data in the depth direction of the living body in the scanning range obtained from the output signal of the photodetector. An optical coherence tomography device having a data storage device, the corneal turbidity analysis device using reflection intensity distribution data by a plurality of scans stored in the data storage device,
Focusing means for focusing light irradiation from the low-coherence light source by the irradiation device on the cornea portion of the eyeball surface;
Reflection intensity discrimination means for comparing each value of the reflection intensity distribution data in the thickness direction of the cornea stored in the data storage device with a predetermined threshold value and classifying the result into normal and abnormal ,
An abnormal number integrating means for calculating the number of abnormal portions for each thickness direction by integrating the number of portions determined to be abnormal by the reflection intensity determining means in the thickness direction;
The number of abnormal parts in the thickness direction of each part in the entire scanning range obtained by the abnormal part integrating means is converted into a density expression, and a density distribution image is displayed on a screen corresponding to the state of the cornea seen from the front. A corneal turbidity analysis device, comprising: The corneal turbidity analysis apparatus according to claim 1, wherein the concentration distribution image display means displays the concentration distribution in a shade of a single color. The irradiation beam scanning by the irradiation device is performed a plurality of times in a concentric manner, and the density distribution image display means includes a coordinate conversion means for converting the position where the integrated value of each abnormal part is obtained into a polar coordinate display. The corneal turbidity analyzer according to claim 1 or 2. A turbidity display means for calculating the total number of the abnormal portions in the entire scanning range and displaying the value corresponding to the total number as corneal turbidity directly or with correction corresponding to the scanning condition is added. The corneal turbidity analyzer according to claim 1, 2 or 3. From the ratio of the part where the number of abnormal parts accumulated by the abnormal part number integrating means is zero and the part which is not zero, the ratio of the part where the abnormal part is not zero in the entire scanning range with respect to the cornea is calculated and corresponds to the ratio 5. The corneal opacity analysis device according to claim 1, further comprising turbid area display means for displaying the value as a corneal turbid area directly or by adding correction corresponding to a scanning condition. The surface part data exclusion means which excludes the data in the range of arbitrary thickness from the surface of the said cornea at the time of the said integration | accumulation in the said abnormal part number integration means is added. Corneal turbidity analyzer. The corneal turbidity analysis apparatus according to claim 6, further comprising a data exclusion range setting means for arbitrarily setting a range in which the number of abnormal portions is excluded by the surface portion data exclusion means.

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