An anterior segment sham elastography method and apparatus

Abstract

This invention discloses a method and device for anterior segment Sham elastography. This invention combines micron-level spatial resolution, high cost-effectiveness, and clinical operability. It can obtain quantitative elastic distribution of anterior segment tissues such as the cornea in vivo and in situ, providing reliable biomechanical basis for ophthalmic diagnosis and treatment scenarios such as early screening of keratoconus, refractive surgery planning, and glaucoma risk assessment. Compared with the prior art, the system structure of this invention is simplified, the cost is significantly reduced, and it has higher resolution and achieves truly non-contact measurement.

Description

Technical Field

[0001] This invention relates to the field of ophthalmic medical imaging technology, and in particular to a method and apparatus for anterior segment Sham elastography. Background Technology

[0002] In ophthalmology, elastography is an imaging technique used to assess the biomechanical properties (such as stress-strain curves and elastic modulus) of ocular tissues, especially the cornea and lens. These properties are crucial for the early diagnosis, risk prediction, and treatment planning of various eye diseases, including keratoconus, glaucoma, cataracts, and refractive surgery evaluation. Currently, the main techniques used for in vivo elastography in ophthalmology are optical coherence elastography and ultrasound elastography.

[0003] Optical coherence elastography (OCE) combines high-resolution (micrometer-scale) OCT imaging with microscale excitation (such as acoustic radiation force, airflow, piezoelectric vibration, etc.) to reconstruct elastic distribution by detecting tissue displacement. However, its system is complex and costly, and has not yet been widely adopted clinically. Ultrasonic elastography, on the other hand, uses a high-frequency ultrasound probe combined with external excitation to measure corneal / lens shear wave velocity to obtain elastic distribution. Due to its insufficient resolution (>50 μm), the need for a coupling medium, and the pressure the probe exerts on the cornea, its clinical ophthalmological applications are extremely limited. Furthermore, the Corvis ST is a corneal biomechanical measurement device that uses a SAM camera to record the entire process of dynamic corneal deformation under airflow pulse excitation. However, it can only acquire the morphology of the upper and lower corneal surfaces, and cannot acquire the strain field inside the cornea. Its spatial resolution is also limited, making it difficult to reflect local heterogeneity, and therefore it cannot be used for high-precision ophthalmic elastography. Summary of the Invention

[0004] This invention provides a method and device for anterior segment Sham elastography, which combines micron-level spatial resolution, high cost-effectiveness, and clinical operability. It can obtain quantitative elastic distribution of anterior segment tissues such as the cornea in vivo and in situ, providing reliable biomechanical basis for ophthalmic diagnosis and treatment scenarios such as early screening of keratoconus, refractive surgery planning, and glaucoma risk assessment.

[0005] A method for anterior segment Sham elastography includes the following steps: S1. Adjust the position of the gaze target based on the refractive state of the eye being tested; S2. A sealed chamber is formed by covering the orbit and including the surface of the anterior segment. The imaging plane of the multi-wavelength Sham imaging device is adjusted so that its optical axis passes through the corneal fixation point and the lens fixation point to obtain an image of the target area with anatomical consistency. S3. Adjust the internal pressure of the sealed cavity according to demand to cause deformation of the cornea and / or lens; S4. During the pressure regulation process, continuously acquire high-resolution image sequences of the anterior segment at different wavelengths and perform multimodal image fusion; S5. After completing step S4, adjust the pressure in the sealed chamber to restore the anterior segment to its initial state. Then repeat S3 and S4 at least twice to obtain at least three sets of SAM imaging data before proceeding to the next step. S6. Based on the Sham imaging data obtained in step S5, calculate the displacement and strain fields of the cornea and / or lens, and combine the actual boundary conditions and tissue elastic constitutive model to quantitatively solve the local elastic parameters through an inversion algorithm to generate elastic imaging results.

[0006] Preferably, the internal pressure adjustment range in S2 is 0 to -300 mmHg.

[0007] Preferably, at least one of the images acquired at different wavelengths in S4 has a clear boundary, and at least one of the images has internal speckle features.

[0008] The S5 Sham imaging data consists of chamber pressure change values ​​and corresponding anterior segment deformation images.

[0009] The S6 method employs full-field displacement and strain analysis, and combines clear boundaries and internal speckle characteristics to calculate the displacement and strain fields of the cornea / lens.

[0010] The full-field displacement and strain analysis method in S6 adopts either digital image correlation or digital volume correlation.

[0011] The specific method for calculating the displacement and strain fields of the cornea and / or lens using the digital image correlation method is as follows: The displacement field is solved by tracking the grayscale changes of the speckle pattern between the reference frame and the deformed frame. ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient:

[0012] in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , ) represents the two-dimensional spatial coordinates of the calculation point. , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; The strain tensor components can be obtained by numerically differentiating the displacement field. This results in a full-field strain distribution that varies with pressure. .

[0013] The specific method for calculating the displacement and strain fields of the cornea and / or lens using the digital volume correlation method is as follows: The displacement field is solved by tracking the grayscale changes of the speckle pattern between the reference frame and the deformed frame. ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient:

[0014] in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , , ) represents the three-dimensional spatial coordinates of the calculation point. , , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; The strain tensor components can be obtained by numerically differentiating the displacement field. This results in a full-field strain distribution that varies with pressure. .

[0015] The method for quantitatively solving the local elastic parameters using the inversion algorithm in S6 is as follows: A two-dimensional axisymmetric finite element model is constructed based on the actual anterior segment geometry. Its geometric boundary is the clear corneal-lens outline obtained by Sham imaging. After image segmentation and smoothing, it is imported into the finite element solver. Given biomechanical parameters, the simulated strain field of the cornea and / or lens is calculated using geometric conditions, boundary conditions, and a tissue elastic constitutive model. ; The actual strain field of the cornea and / or lens calculated using the full-field displacement and strain analysis method To achieve this goal, the parameters of the organizational elastic constitutive model are adjusted through an iterative optimization algorithm. Reduce the simulated strain field obtained by finite element forward simulation. With the actual strain field The residual values ​​between; When the residual converges to the preset threshold, the optimal parameters are output. This refers to the quantitative elastic parameters of the cornea / lens of the subject. The optimal parameters obtained from the inversion Mapping to spatial location and combining with the original anatomical images to generate quantitative elastography maps.

[0016] The iterative optimization algorithm uses the following formula:

[0017] in, The number of sampling points is the total area of ​​the region of interest in the cornea and lens divided by the Sham imaging resolution.

[0018] The actual boundary conditions are set as follows: the limbus region is fixed and constrained; the equatorial portion of the lens is free; and the anterior surface of the cornea is subjected to a uniformly distributed negative pressure load. p The direction is perpendicular to the local surface; the posterior surface of the cornea and the surface of the lens bear the intraocular pressure. IOP The direction is perpendicular to the local surface.

[0019] The constitutive model for organizational resilience is either the Ogden model or the HGO model.

[0020] The tissue elastic constitutive model adopts the first-order Ogden hyperelastic model, and its strain energy function is expressed as:

[0021] in, ( The main elongation is... For parameters related to shear modulus, The two are nonlinear exponents, and together they constitute the biomechanical parameter vector to be inverted. .

[0022] The tissue elastic constitutive model adopts the HGO model, and its strain energy function is expressed as: Cauchy–Green

[0023] ; and Material parameters characterizing the mechanical response of non-fiber matrices; , ( () represents the strengthening parameters corresponding to the two groups of collagen fiber families; , is a fiber dispersion parameter used to describe the degree of concentration of collagen fiber orientation; The biomechanical parameter vector to be inverted is .

[0024] An anterior segment Sham elastography device, comprising: An imaging apparatus for acquiring images of the anterior segment, comprising illumination and a camera. An environmental pressure control device for producing a sealed chamber that covers the anterior segment of the eye and for regulating the pressure inside the sealed chamber, comprising a sealed chamber, a pressure regulating assembly and a pressure sensor. The imaging aid includes a gaze target module and a coaxial imaging module for guiding the patient's gaze and adjusting the position of the Sham imaging, respectively; and The mechanical inversion device acquires the image sequence and corresponding negative pressure values ​​collected by the imaging device, and calculates the full-field displacement and strain field of the cornea / lens during the loading process.

[0025] Preferably, the illumination is multi-wavelength slit lamp illumination, including at least one wavelength for acquiring a clear boundary of the image and at least one or more wavelengths for acquiring speckle features within the image.

[0026] Preferably, the gaze target module includes a light source, a diffuser, a pinhole, and an imaging lens arranged in sequence, wherein the light source is used to illuminate the pinhole, the diffuser is used to homogenize the distribution of the illumination light, and the illuminated pinhole is focused onto the fundus of the human eye by the imaging lens.

[0027] Compared with the prior art, the beneficial effects of the present invention are: the present invention integrates the entire process from controllable environmental pressure loading, high-precision multimodal Sham imaging to quantitative elastic parameter inversion, which significantly improves the accuracy and clinical applicability of anterior segment biomechanical assessment; This invention achieves non-contact controllable mechanical loading, completing a breakthrough from deformation observation to quantitative elastic imaging, and can accurately invert biomechanical parameters such as elastic modulus; without physical pressure or coupling medium, it can simulate different physiological and mechanical conditions. Attached Figure Description

[0028] Figure 1 This is a flowchart of the process of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is a schematic diagram of the anterior segment Sham elastography device.

[0029] Explanation of reference numerals in the attached figures: 1-Imaging device; 2-Ambient pressure control device, 21-Sealed chamber, 22-Pressure regulating component, 23-Pressure sensor; 3-Imaging aid device, 31-Gazing target module, 32-Coaxial imaging module; 4-Mechanical inversion device; 5-Anterior segment. Detailed Implementation

[0030] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0031] Example 1 like Figure 1 As shown in the figure, an anterior segment Sham elastography method provided by an embodiment of the present invention includes the following steps: S1. Adjust the position of the gaze target based on the refractive state of the eye being tested; This step adjusts the position of the fixation target according to the refractive state of the eye being tested, guides the subject to fixate on the target, and puts the suspensory ligament in a completely relaxed state, thereby simulating the physiological conditions of near vision and ensuring that the lens is in a stable and repeatable initial shape. S2. A sealed chamber is formed by covering the orbit and including the surface of the anterior segment. The imaging plane of the multi-wavelength Sham imaging device is adjusted so that its optical axis passes through the corneal fixation point and the lens fixation point to obtain an image of the target area with anatomical consistency. This step involves creating a sealed chamber that covers the orbit and includes the surface of the anterior segment. Simultaneously, the subject is guided to continuously focus on the target to keep the eyeball still, allowing for real-time observation of the anterior segment structure. Based on this, the imaging plane of the multi-wavelength Sham imaging device is precisely adjusted to ensure that its optical axis passes through the corneal apex and the lens apex, in order to obtain an image of the target area with anatomical consistency. S3. Adjust the internal pressure of the sealed cavity according to demand to cause deformation of the cornea and / or lens; This step induces controllable deformation of the cornea and / or lens at a target strain rate by adjusting the internal air pressure of the sealed chamber formed in S2; wherein the air pressure ranges from 0 to... 300 mmHg, the target strain rate generated by the cornea and / or lens is 0.001 s⁻¹. - ¹ up to 100s - ¹; S4. During the pressure regulation process, continuously acquire high-resolution image sequences of the anterior segment at different wavelengths and perform multimodal image fusion; During the process of adjusting the pressure change inside the sealed chamber in step S3, the multi-wavelength Sham imaging system is simultaneously activated to continuously acquire high-resolution image sequences of the anterior segment at different wavelengths with an adjustable frame rate of 20–5000fps. At least one wavelength is used to obtain clear boundaries, and at least one wavelength or the remaining wavelengths are used to capture internal speckle features and perform multimodal image fusion. S5. After completing step S4, adjust the pressure in the sealed chamber to restore the anterior segment to its initial state. Then repeat S3 and S4 at least twice to obtain at least three sets of SAM imaging data before proceeding to the next step. After completing one loading-imaging process, the sealed chamber is completely depressurized to restore the anterior segment to its initial state. Then, the negative pressure pump is restarted, and S3 to S4 are repeated. This cycle is repeated at least twice to obtain no fewer than two sets of highly repeatable SAM imaging data under the same environmental pressure loading conditions for reliability verification in subsequent analysis. The SAM imaging data consists of chamber pressure change values ​​and corresponding anterior segment deformation images. S6. Based on the Sham imaging data obtained in step S5, calculate the displacement field and strain field of the cornea / lens, and combine the actual boundary conditions and tissue elastic constitutive model to quantitatively solve the local elastic parameters through the inversion algorithm to generate elastic imaging results. This step, based on multiple sets of stable measurement data obtained in S5 (including synchronously recorded chamber pressure changes and corresponding anterior segment deformation images), utilizes the mechanical inversion module and employs full-field displacement and strain analysis methods (such as digital image correlation (DIC) or digital volume correlation (DVC), combined with clear boundary and internal speckle characteristics, to calculate the displacement and strain fields of the cornea / lens; further, combining actual boundary conditions and tissue elastic constitutive models (hyperelastic constitutive models such as Ogden and HGO), the local elastic parameters are quantitatively solved through inversion algorithms, ultimately generating high-resolution, quantitative elastic imaging results; The full-field displacement and strain analysis method in S6 of this embodiment uses digital image correlation to track the speckle pattern in the reference frame (unloaded state) and the deformation frame (loaded pressure). Solve the displacement field by considering the grayscale changes between (below) and (top). ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient:

[0032] in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , ) represents the two-dimensional spatial coordinates of the calculation point. , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; By numerically differentiating the displacement field, the strain tensor components (such as...) can be obtained. This forms a global strain distribution that varies with pressure. ; In other embodiments, S4 also acquires three-dimensional morphological data of the membrane and lens. In this case, digital volume correlation combined with three-dimensional Sham imaging is used to obtain the three-dimensional displacement and strain fields of the anterior segment tissue during pressure loading. Furthermore, using a finite element inverse analytical method similar to the above, based on the three-dimensional geometric model, real boundary conditions, and hyperelastic constitutive relations, the spatial distribution elastic parameters of the cornea and / or lens are inverted to obtain the three-dimensional quasi-static Sham elastography of the anterior segment, as detailed below: The displacement field is solved by tracking the grayscale changes of the speckle pattern between the reference frame and the deformed frame. ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient:

[0033] in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , , ) represents the three-dimensional spatial coordinates of the calculation point. , , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; The strain tensor components can be obtained by numerically differentiating the displacement field. This results in a full-field strain distribution that varies with pressure. ; Subsequently, the hyperelastic parameters of the biological tissue were inverted using the finite element inverse analytical method, as detailed below: A two-dimensional axisymmetric finite element model consistent with the actual anterior segment geometry was constructed. Its geometric boundary was accurately extracted from the clear corneal-lens contour obtained by Sham imaging and then imported into the finite element solver after image segmentation and smoothing. The actual boundary conditions are set as follows: the limbus region is set as a fixed constraint; the equatorial region of the lens is in a free state; the anterior surface of the cornea is subjected to a uniformly distributed negative pressure load. p The direction is perpendicular to the local surface; the posterior surface of the cornea and the surface of the lens bear the intraocular pressure. IOP The direction is perpendicular to the local surface; The organizational elastic constitutive model used in this embodiment is the first-order Ogden hyperelastic model, whose strain energy function is expressed as:

[0034] in, ( The main elongation is... For parameters related to shear modulus, The two are nonlinear exponents, and together they constitute the biomechanical parameter vector to be inverted. This model is suitable for describing the hyperelastic behavior of the cornea and lens. In some other embodiments, the HGO model is used, and its strain energy function is expressed as: Cauchy–Green

[0035] ; and Material parameters characterizing the mechanical response of non-fiber matrices; , ( () represents the strengthening parameters corresponding to the two groups of collagen fiber families; , is a fiber dispersion parameter used to describe the degree of concentration of collagen fiber orientation; The biomechanical parameter vector to be inverted is .

[0036] In the finite element inverse analysis process, given biomechanical parameters, the corneal / lens strain field can be calculated using the aforementioned geometric conditions, actual boundary conditions, and tissue elastic constitutive model. ; Measured strain field obtained by full-field displacement and strain analysis method To achieve the goal, the parameters of the constitutive model are adjusted using the Levenberg-Marquardt iterative optimization algorithm. This makes the strain field obtained by the finite element forward simulation... Minimize the residual between the experimental and measured values:

[0037] in, The number of sampling points is calculated by dividing the total area of ​​the cornea and lens region of interest by the Sham imaging resolution; the optimal parameters are output when the residual converges to a preset threshold. This refers to the quantitative elastic parameters of the cornea / lens of the subject. The inversion obtained and Mapping to spatial location and combining with the original anatomical images to generate quantitative elastography maps; In other embodiments, the loading rate of the negative pressure within the sealed chamber is increased (e.g., the strain rate is increased to 1 s). -¹ and above), can stimulate the dynamic mechanical response of the anterior segment tissue; combined with high frame rate (e.g. ≥1000fps) multi-wavelength Sham imaging and DIC / DVC analysis, it can also capture transient deformation processes, realize dynamic Sham elastic imaging of the anterior segment, and be used to evaluate the viscoelastic or inertial effects of tissue under rapid loading conditions.

[0038] Example 2 like Figure 2 and Figure 3 As shown, this embodiment discloses an anterior segment Sham elastography device, including an imaging device, an environmental pressure control device, an imaging aid device, and a mechanical inversion device. Among them, the imaging device 1 (multi-wavelength Sham imaging device) is used to simultaneously acquire high-resolution images of anterior segment tissue with clear anatomical boundaries and internal speckle features, and has an image fusion function to integrate information from different wavelength working modes, including illumination and camera. The illumination is multi-wavelength slit lamp illumination, which includes at least one wavelength for acquiring clear image boundaries and at least one or more wavelengths for acquiring speckle features within the image. This embodiment uses dual-wavelength slit lamp illumination as an example. One light source has a broadband wavelength, and the other has a narrowband wavelength. The broadband wavelength is low-coherence light with a wavelength of 470±10nm, used to acquire images that accurately depict the boundaries of the cornea / lens. The narrowband wavelength is high-coherence light with a wavelength of 850±3nm, used to capture speckle images reflecting the microstructure of collagen fibers within the tissue. Through image processing algorithms, these image information obtained under different wavelength conditions are fused to generate a comprehensive image that not only clearly shows the fine anatomical boundaries of the cornea or lens but also reveals its complex internal collagen fiber structure. Additionally, the camera's focal length is 50-60mm, which, when used with a camera lens, can achieve 12... A 12mm field of view with lateral and axial resolution ≤20μm; capable of 2D imaging frame rates of 20-5000fps, where low frame rates (e.g., 20–100fps) are suitable for quasi-static 2D elastic imaging, and high frame rates (e.g., ≥1000fps) are suitable for dynamic 3D elastic imaging. An environmental pressure regulating device 2 is used to produce a sealed chamber that covers the anterior segment of the eye and to regulate the pressure inside the sealed chamber. It includes a sealed chamber 21, a pressure regulating component 22, and a pressure sensor 23. The sealed chamber in this embodiment can be composed of quartz flat glass, resin sidewalls that can conform to the contour of the subject's eye socket, and soft skirts. When negative pressure is established by the pressure regulating component, the soft skirts of the resin sidewalls conform to the contour of the subject's eye socket to form a sealed space. The pressure regulating component uses a negative pressure pump, which draws gas from the sealed chamber through a pipeline, completing a uniform negative pressure loading from 0 to -300 mmHg within a preset time (10 seconds in this embodiment). The strain rate of the cornea and lens is approximately 0.001 s. - ¹; The negative pressure loading rate is controlled in a closed loop based on the pressure sensor readings; The imaging assist device 3 includes a gaze target module 31 and a coaxial imaging module 32, which are used to guide the patient's gaze and adjust the position of the Sham imaging, respectively. The imaging assist device guides the patient's gaze through the gaze target to fix the cornea, and adjusts the position of the Sham imaging through coaxial imaging to ensure that the imaging area passes through the corneal apex. The coaxial imaging module uses a lens and camera combination to achieve a field of view with a diameter of 15mm and a lateral resolution of ≤25μm; The fixation target module consists of a light source, a diffuser, a pinhole, and an imaging lens. The light source illuminates the pinhole, and the diffuser homogenizes the illumination light distribution. The illuminated pinhole is focused onto the fundus of the human eye through the imaging lens. The imaging lens can be moved to adjust the focus. Depending on the patient's degree of myopia, and according to the calibrated position, the pinhole image can be projected onto the patient's fundus, simulating an illumination target at a distance of 7-10 cm in front of the eyes, thus achieving the purpose of relaxing the suspensory ligaments. The mechanical inversion device 4 employs a computer processing system. Based on the acquired continuous-frame multi-wavelength Sham imaging fusion images and corresponding environmental pressures, it utilizes full-field displacement and strain analysis methods (such as Digital Image Correlation (DIC) or Digital Volume Correlation (DVC), combined with clear boundary contours and internal speckle features, to calculate the three-dimensional displacement field of the cornea / lens under pressure excitation, and further derives the strain field distribution. On this basis, combining actual boundary conditions and known corneal / lens elastic constitutive models, the local elastic parameters of the tissue are solved using a mechanical inversion algorithm, ultimately achieving high-resolution, quantitative elastic imaging. Specific methods are described in Example 1 above, and will not be repeated here. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for anterior segment Sham elastography, characterized in that, Includes the following steps: S1. Adjust the position of the gaze target based on the refractive state of the eye being tested; S2. A sealed chamber is formed by covering the orbit and including the surface of the anterior segment. The imaging plane of the multi-wavelength Sham imaging device is adjusted so that its optical axis passes through the corneal fixation point and the lens fixation point to obtain an image of the target area with anatomical consistency. S3. Adjust the internal pressure of the sealed cavity according to demand to cause deformation of the cornea and / or lens; S4. During the pressure regulation process, continuously acquire high-resolution image sequences of the anterior segment at different wavelengths and perform multimodal image fusion; S5. After completing step S4, adjust the pressure in the sealed chamber to restore the anterior segment to its initial state. Then repeat S3 and S4 at least twice to obtain at least three sets of SAM imaging data before proceeding to the next step. S6. Based on the Sham imaging data obtained in step S5, calculate the displacement and strain fields of the cornea and / or lens, and combine the actual boundary conditions and tissue elastic constitutive model to quantitatively solve the local elastic parameters through an inversion algorithm to generate elastic imaging results.

2. The anterior segment Sham elastography method as described in claim 1, characterized in that, The internal pressure adjustment range of S2 is 0 to -300 mmHg.

3. The anterior segment Sham elastography method as described in claim 1, characterized in that, At least one of the images acquired at different wavelengths in S4 has a clear boundary, and at least one of the images has internal speckle features.

4. The anterior segment Sham elastography method as described in claim 1, characterized in that, The S5 Sham imaging data consists of chamber pressure change values ​​and corresponding anterior segment deformation images.

5. The anterior segment Sham elastography method as described in claim 3, characterized in that, The S6 method employs full-field displacement and strain analysis, and combines clear boundaries and internal speckle characteristics to calculate the displacement and strain fields of the cornea / lens.

6. The anterior segment Sham elastography method as described in claim 5, characterized in that, The full-field displacement and strain analysis method in S6 adopts either digital image correlation or digital volume correlation.

7. The anterior segment Sham elastography method as described in claim 6, characterized in that, The specific method for calculating the displacement and strain fields of the cornea and / or lens using the digital image correlation method is as follows: The displacement field is solved by tracking the grayscale changes of the speckle pattern between the reference frame and the deformed frame. ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient: in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , ) represents the two-dimensional spatial coordinates of the calculation point. , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; The strain tensor components can be obtained by numerically differentiating the displacement field. This results in a full-field strain distribution that varies with pressure. .

8. The anterior segment Sham elastography method as described in claim 6, characterized in that, The specific method for calculating the displacement and strain fields of the cornea and / or lens using the digital volume correlation method is as follows: The displacement field is solved by tracking the grayscale changes of the speckle pattern between the reference frame and the deformed frame. ; Its basic optimization objective is to minimize the normalized cross-correlation coefficient: in, and These are the grayscale functions of the reference image and the deformed image, respectively. For region of interest, p The negative pressure load on the anterior surface of the cornea, , , ) represents the three-dimensional spatial coordinates of the calculation point. , , () represents the displacement of the calculated point relative to the reference frame in the deformed frame; The strain tensor components can be obtained by numerically differentiating the displacement field. This results in a full-field strain distribution that varies with pressure. .

9. The anterior segment Sham elastography method as described in claim 1, characterized in that, The method for quantitatively solving the local elastic parameters using the inversion algorithm in S6 is as follows: A two-dimensional axisymmetric / three-dimensional finite element model is constructed based on the actual anterior segment geometry. Its geometric boundary is the clear corneal-lens outline obtained by Sham imaging. After image segmentation and smoothing, it is imported into the finite element solver. Given biomechanical parameters, the simulated strain field of the cornea and / or lens is calculated using geometric conditions, boundary conditions, and a tissue elastic constitutive model. ; The actual strain field of the cornea and / or lens calculated using the full-field displacement and strain analysis method To achieve this goal, the parameters of the organizational elastic constitutive model are adjusted through an iterative optimization algorithm. Reduce the simulated strain field obtained by finite element forward simulation. With the actual strain field The residual values ​​between; When the residual converges to the preset threshold, the optimal parameters are output. This refers to the quantitative elastic parameters of the cornea / lens of the subject. The optimal parameters obtained from the inversion Mapping to spatial location and combining with the original anatomical images to generate quantitative elastography maps.

10. The anterior segment Sham elastography method as described in claim 9, characterized in that, The iterative optimization algorithm uses the following formula: in, The number of sampling points is the total area of ​​the region of interest in the cornea and lens divided by the Sham imaging resolution.

11. The anterior segment Sham elastography method as described in claim 1, characterized in that, The actual boundary conditions are set as follows: the limbus region is fixed and constrained; the equatorial portion of the lens is free; and the anterior surface of the cornea is subjected to a uniformly distributed negative pressure load. p The direction is perpendicular to the local surface; the posterior surface of the cornea and the surface of the lens bear the intraocular pressure. IOP The direction is perpendicular to the local surface.

12. The anterior segment Sham elastography method as described in claim 1, characterized in that, The constitutive model for organizational resilience is either the Ogden model or the HGO model.

13. The anterior segment Sham elastography method as described in claim 12, characterized in that, The tissue elastic constitutive model adopts the first-order Ogden hyperelastic model, and its strain energy function is expressed as: in, ( The main elongation is... For parameters related to shear modulus, The two are nonlinear exponents, and together they constitute the biomechanical parameter vector to be inverted. .

14. The anterior segment Sham elastography method as described in claim 12, characterized in that, The tissue elastic constitutive model adopts the HGO model, and its strain energy function is expressed as: Cauchy–Green ； and Material parameters characterizing the mechanical response of non-fiber matrices; , ( () represents the strengthening parameters corresponding to the two groups of collagen fiber families; , is a fiber dispersion parameter used to describe the degree of concentration of collagen fiber orientation; The biomechanical parameter vector to be inverted is .

15. An anterior segment Sham elastography device, characterized in that, include: An imaging apparatus for acquiring images of the anterior segment, comprising illumination and a camera. An environmental pressure control device for producing a sealed chamber that covers the anterior segment of the eye and for regulating the pressure inside the sealed chamber, comprising a sealed chamber, a pressure regulating assembly and a pressure sensor. An imaging aid includes a gaze target module and a coaxial imaging module, which are used to guide the patient’s gaze and adjust the position of the Sham imaging, respectively. as well as The mechanical inversion device acquires the image sequence and corresponding negative pressure values ​​collected by the imaging device, and calculates the full-field displacement and strain field of the cornea / lens during the loading process.

16. The anterior segment Sham elastography device as described in claim 15, characterized in that, The illumination is multi-wavelength slit lamp illumination, including at least one wavelength for obtaining a clear boundary of the image and at least one or more wavelengths for obtaining speckle features within the image.

17. The anterior segment Sham elastography device as described in claim 15, characterized in that, The gaze target module includes a light source, a diffuser, a pinhole, and an imaging lens arranged in sequence. The light source is used to illuminate the pinhole, the diffuser is used to homogenize the distribution of the illumination light, and the illuminated pinhole is focused onto the fundus of the human eye by the imaging lens.

Images