A special base for tensile machine to detect the elasticity of small animal lens and analysis method

Abstract

The application provides a special base for a tensile testing machine to detect the elasticity of small animal lenses and an analysis method, and relates to the field of soft tissue mechanics. The special base comprises a base body, a lens supporting part and a limiting structure. The lens supporting part is provided with a concave supporting groove matched with the shape of a lens to be detected, which is used for accommodating the lens to be detected and performing initial positioning. The limiting structure is arranged at the outer edge area of the supporting groove to limit the lateral displacement during the compression process to reduce the side slip. The inner surface of the supporting groove is provided with a flexible contact layer to reduce local stress concentration. The application effectively solves the problems of easy side slip of soft tissue under compression and large artificial selection error of the fitting interval.

Description

Technical Field

[0001] This invention relates to the field of soft tissue mechanics, and in particular to a special base and analytical method for testing the elasticity of the lens of small animals using a tensile testing machine. Background Technology

[0002] Changes in the biomechanical properties of the lens are closely related to the pathological progression of presbyopia and cataracts. In basic ophthalmology experiments, researchers routinely use tensile testing machines to perform compression tests on isolated lenses from small animals, thereby quantitatively assessing the evolution of lens hardness.

[0003] Current methods for testing lens mechanics have significant structural limitations and data processing deficiencies.

[0004] Firstly, regarding the hardware load-bearing aspect, the isolated lens of a small animal has a near-spherical structure and its surface is covered with slippery tissue fluid. When the isolated lens is placed directly on the flat sample stage of a conventional tensile testing machine, as the indenter gradually descends and applies a compressive load, the isolated lens is highly prone to uncontrollable lateral slippage on the flat sample stage. This slippage forces the loading axis of the tensile testing machine indenter to deviate significantly from the geometric center of the lens, causing eccentric compression of the test sample and resulting in extremely low test repeatability.

[0005] Secondly, at the data analysis level, the isolated lens, as a typical biological soft tissue, exhibits a highly nonlinear deformation response in the initial stage of compression. Current common data processing procedures rely on the subjective experience of experimenters, manually identifying and selecting an approximately straight segment from the original load-displacement curve to perform slope fitting. This manual selection method, lacking objective quantitative screening standards, cannot mask the subjective differences in judgment between different operators, resulting in significant fluctuations in the final calculated elastic characteristic parameters. This renders the biomechanical data from different batches of experimental groups uncomparable scientifically. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a special base and analysis method for testing the elasticity of the lens of small animals using a tensile testing machine. This invention solves the problems of easy lateral slippage and displacement of the lens under pressure and large subjective errors in the manual selection of the elasticity fitting range in the prior art.

[0007] To achieve the above objectives, the present invention provides the following solution: A dedicated base for testing the elasticity of the lens of small animals using a tensile testing machine, comprising: The base body is fixed to the sample stage of the tensile testing machine; A lens support portion is disposed on the base body. The lens support portion has an upwardly opening support groove. The inner surface of the support groove has a concave structure that adapts to the shape of the lens to be tested, and is used to accommodate the lower half of the lens to be tested and to initially position the lens to be tested. A limiting structure is provided in the outer edge region of the support groove to limit the lateral displacement of the lens under test during the pressure test, so as to reduce lateral slippage.

[0008] An analytical method for testing the elasticity of the lens of small animals using a tensile testing machine, the analytical method comprising: Place the isolated lens to be tested in the support groove of the special base, so that the center of the isolated lens is located on the loading axis of the tensile testing machine head; Adjust the initial position of the tensile testing machine indenter and perform preload or zero-point calibration; The tensile testing machine is controlled to vertically compress the isolated lens at a preset speed, and the original load-displacement data is collected in real time. The original load-displacement data is denoised, and the derivative of the denoised original load-displacement data is calculated to automatically identify and extract continuous linear response segments where the derivative value fluctuation is less than a preset fluctuation threshold, so as to obtain the target load-displacement data. A linear regression fitting algorithm was used to fit the target load-displacement data and extract the slope, and the elasticity-related parameters of the lens were calculated. The lens elasticity parameters include: initial stiffness, apparent elastic coefficient, load corresponding to a specific displacement, compression corresponding to a specific load, and characteristic slope of the load-displacement curve.

[0009] The present invention discloses the following technical effects: This invention provides a dedicated base and analysis method for testing the elasticity of the lens of small animals using a tensile testing machine. By configuring a dedicated base with concave support grooves and limiting structures, this invention achieves adaptive centering constraint on the slippery, spherical lens, effectively curbing lateral displacement during compression and ensuring precise alignment of the tensile testing machine's loading axis with the lens's geometric center. This significantly improves the physical stability and data repeatability of soft tissue biomechanical testing. Secondly, addressing the technical problem of large subjective errors in manually selecting elasticity fitting intervals, this method automatically locks the continuous linear response segment using a derivative variance determination mechanism and combines this with the base's unique curvature to calculate the elasticity formula. This completely eliminates human experience intervention, achieving ultimate standardization and objectivity in the extraction of elasticity characteristic parameters, and effectively ensuring the scientific comparability of biomechanical data from different batches. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of a special base structure for testing the elasticity of the lens of small animals using a tensile testing machine, provided in an embodiment of the present invention. Figure 2 This is a flowchart of an analytical method for testing the elasticity of the lens of a small animal using a tensile testing machine, provided as an embodiment of the present invention.

[0012] Figure label: 1-Base body, 2-Lens support, 3-Lens to be tested, 4-Limiting structure. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] like Figure 1 As shown, the present invention provides a special base for testing the elasticity of the lens of small animals using a tensile testing machine, characterized in that it comprises: The base body 1 is fixed on the sample stage of the tensile testing machine; The lens support part 2 is disposed on the base body 1. The lens support part 2 has an upwardly opening support groove. The inner surface of the support groove has a concave structure that is adapted to the shape of the lens 3 to be tested, and is used to accommodate the lower half of the lens 3 to be tested and to initially position the lens 3 to be tested. The limiting structure 4 is disposed in the outer edge region of the support groove to limit the lateral displacement of the lens 3 under test during the pressure test, so as to reduce lateral slippage.

[0016] Furthermore, a flexible contact layer is provided on the inner surface of the support groove; The flexible contact layer is any one of a silicone layer, an elastic membrane, and a hydrogel layer; The flexible contact layer is used to improve the contact state between the lens under test 3 and the dedicated base, so as to reduce the local stress concentration of the lens under test 3 during the pressure test.

[0017] Specifically, this embodiment provides a dedicated base for testing the elasticity of the lens of small animals using a tensile testing machine. The main structure of the base is built upon the base body 1. The base body 1 is manufactured in one piece using medical-grade stainless steel. A standard threaded interface is machined on the bottom surface of the base body 1, which rigidly fixes it to the sample stage of the tensile testing machine, thus completely eliminating basic deformation errors during the compression test. To ensure the overall physical stability of the alignment test, the outer contour of the base body 1 is a solid cylinder, with its bottom diameter strictly set at 30 mm and its overall height set at 15 mm. This geometric configuration adapts to the sample stages of conventional tensile testing machines on the market while providing sufficient self-weight, ensuring the absolute stability of the device under dynamic compressive loads.

[0018] The lens support 2 is fixedly disposed at the top center of the base body 1. The lens support 2 has an upward-opening support groove, and the inner surface of the support groove has a concave structure adapted to the shape of the lens 3 to be tested. In order to achieve high-precision accommodation and initial positioning of the lower half of the lens 3 to be tested, this embodiment performs spatial dimension mapping processing on the three-dimensional morphology of the concave structure. The specific mapping process is as follows: the average equatorial plane diameter and average sagittal plane thickness of the isolated lens of a rat of a specific age are extracted as morphological basis data. The morphological basis data is enlarged proportionally in three-dimensional space according to a scaling factor of 1.1, and the enlarged values ​​are used as the processing surface parameters of the concave structure. Based on the above mapping data processing, for 12-week-old adult rats, the concave structure is precisely customized as a semi-ellipsoidal pit, with the major axis diameter at the opening limited to 6 mm, the minor axis diameter limited to 5 mm, and the maximum central depth limited to 2.5 mm.

[0019] The limiting structure 4 is integrally formed and disposed on the outer edge of the support groove. Specifically, the limiting structure 4 is an annular baffle surrounding the edge of the opening of the support groove. During the compression test, as the pressure head above the tensile testing machine continues to descend, the lens under test 3 is easily subjected to vertical compressive force, which can easily generate a horizontal escape component force. The annular baffle forms a rigid physical boundary to directly prevent the lens under test 3 from lateral displacement, thereby reducing and eliminating the side slip phenomenon. In order to achieve effective interception while absolutely avoiding interference with the normal downward stroke of the tensile testing machine pressure head, the vertical height of the annular baffle above the top plane of the base body 1 is set to 1.2 mm, and the radial wall thickness of the annular baffle is set to 0.8 mm, thereby forcing the geometric center of the lens under test 3 to always remain on the force axis, where F is the direction of force application.

[0020] To improve the rigid contact between the lens under test 3 and the dedicated base, a flexible contact layer is conformally covered and attached to the inner surface of the support groove. In this embodiment, the flexible contact layer is a polyvinyl alcohol hydrogel layer. As a fragile biological soft tissue, the isolated lens experiences significant pressure when in direct contact with a rigid metal surface, even on a very small contact area. The polyvinyl alcohol hydrogel layer, through its own elastic deformation, transforms the point contact at the bottom of the lens under test 3 into a uniform surface contact, significantly reducing local stress concentration during the pressure test. In this embodiment, the thickness of the polyvinyl alcohol hydrogel layer is precisely controlled at 0.5 mm. This specific thickness provides sufficient buffer energy absorption space while avoiding macroscopic displacement errors introduced into the measurement system due to excessive compression of the flexible layer itself.

[0021] In the actual assembly and testing phase of this embodiment, the lens under test 3 sinks to the surface of the polyvinyl alcohol hydrogel layer under its own gravity, completing the initial adaptive positioning. At this time, an absolutely vertical centering reference line is established between the geometric lowest point of the bottom of the concave structure and the center point of the tensile testing machine head. When the tensile testing machine head applies a load downward at a constant rate, the outer contour of the bottom of the lens under test 3 undergoes dynamic conformation deformation with the polyvinyl alcohol hydrogel layer. The contact stress distribution area gradually expands concentrically from the geometric lowest point outwards until the equatorial edge of the lens under test 3 abuts against the inner wall of the limiting structure 4. Through the physical coordination of all the above structures, this embodiment strictly limits the maximum lateral slippage distance of the lens under test 3 to within 0.1 mm, ensuring the physical authenticity of the load and displacement data finally collected by the system.

[0022] like Figure 2 As shown, this embodiment also provides an analytical method for testing the elasticity of the lens of a small animal using a tensile testing machine. The analytical method includes: Step 100: Place the isolated lens to be tested in the support groove of the special base, so that the center of the isolated lens is located on the loading axis of the tensile testing machine head; Step 200: Adjust the initial position of the tensile testing machine indenter and perform preload or zero-point calibration; Step 300: Control the tensile testing machine to vertically compress the isolated lens at a preset speed, and collect the original load-displacement data in real time; Step 400: Denoise the original load-displacement data and calculate the derivative of the denoised original load-displacement data to automatically identify and extract continuous linear response segments where the derivative value fluctuation is less than a preset fluctuation threshold, thereby obtaining the target load-displacement data. Step 500: Use a linear regression fitting algorithm to fit the target load-displacement data and extract the slope, and calculate the lens elasticity-related parameters; The lens elasticity parameters include: initial stiffness, apparent elastic coefficient, load corresponding to a specific displacement, compression corresponding to a specific load, and characteristic slope of the load-displacement curve.

[0023] Furthermore, the specific implementation process of step 100 is as follows: When performing the analytical method provided in this embodiment, the spatial positioning of the sample is performed first. The experimenter uses blunt-tipped micro-tweezers to transfer the isolated lens to be tested, from which attached tissue has been removed, and places it into the support groove of the dedicated base fixed on the sample stage of the tensile testing machine. During the transfer and placement stage, a quantitative amount of isothermal saline is pre-dropped onto the surface of the isolated lens to be tested; the amount added is precisely controlled between 0.05 ml and 0.1 ml. This isothermal saline forms a uniform liquid protective film around the lens, preventing the biological soft tissue from dehydrating and hardening in ambient air, and providing the necessary physical lubrication interface for subsequent sliding positioning.

[0024] After the isolated lens under test enters the support groove, the system immediately triggers and adaptively centers it based on the concave shape of the support groove. Specifically, since the isolated lens under test is nearly spherical and has a liquid lubricating film on its surface, it slides down the smooth inner wall of the support groove under its own gravity. After approximately 2 to 3 seconds of natural settling, the convex curved surface at the bottom of the isolated lens under test finally conforms to and stops at the geometric lowest point of the bottom of the support groove, thus establishing the initial physical alignment state. In this embodiment, the specific definition of the initial physical alignment state is: the perpendicular line from the geometric center of the isolated lens under test and the central axis of symmetry of the support groove achieve preliminary spatial coincidence, and the horizontal distance deviation between them is forcibly converged by the mechanical structure and constrained within a tolerance range of 0.2 mm.

[0025] After establishing the initial physical alignment, the servo drive of the tensile testing machine is controlled to drive the machine's indenter downwards at a constant speed in the vertical direction. To completely prevent the indenter from accidentally impacting and irreversibly crushing fragile soft tissue samples when misaligned, this embodiment has a preset observation height fixed in the control logic of the device. The preset observation height is strictly defined as: the spatial hovering position where the lower working surface of the tensile testing machine's indenter is exactly 2 mm above the theoretical vertex of the isolated lens to be tested. When the position sensor detects that the tensile testing machine's indenter has reached this specific spatial coordinate, the servo drive immediately performs automatic braking, providing a safe physical gap for subsequent high-precision manual or optical inspection.

[0026] With the tensile testing machine indenter stably suspended at the preset observation height, a high-definition camera based on orthogonal binocular vision checks the coaxiality deviation between the center point of the indenter and the actual highest vertex of the isolated lens under test. Based on the deviation value detected, the operating mechanism synchronously drives a high-precision bidirectional moving platform located at the bottom of the dedicated base. Based on the residual deviation from the initial physical alignment, the horizontal spatial position of the dedicated base is fine-tuned along the horizontal and vertical planes. This fine-tuning process iterates until it is confirmed that the highest vertex of the isolated lens under test is precisely aligned with the loading axis of the tensile testing machine indenter. In this embodiment, the quantitative closed-loop control threshold for precise alignment is defined as an absolute spatial deviation of less than 0.02 mm between the two axes.

[0027] Through the dual spatial positioning mechanism that combines gravity-based adaptive settling with visual feedback-based horizontal fine-tuning, this embodiment completely eliminates uncontrollable factors such as random rolling or force deflection of the isolated lens sample on a flat testing platform. This perfectly determined orthogonal alignment ensures that, during the subsequent vertical compression step, the downward vertical pressure output by the indenter passes through the core force axis of the isolated lens under test absolutely vertically and uniformly. This implementation step eliminates, at its physical source, the lateral flipping of the sample and local stress distortion caused by eccentric loading, laying a crucial foundation for the acquisition system to obtain biomechanical raw load and displacement data with extremely high inter-group repeatability.

[0028] Furthermore, the specific implementation process of step 200 is as follows: In this embodiment, after confirming that the isolated lens under test has achieved initial physical alignment, the calibration process begins by adjusting the initial position of the tensile testing machine indenter. This embodiment controls the tensile testing machine indenter to approach the isolated lens along the vertically downward loading axis at a preset calibration speed. The preset calibration speed refers to the unloaded descent rate before physical contact occurs; its function is to balance the time efficiency of the calibration process with avoiding irreversible mechanical damage to fragile biological soft tissue caused by high-speed impact. In this embodiment, the preset calibration speed is set to 0.5 mm / s. Throughout the entire dynamic process of the tensile testing machine indenter's descent, this embodiment continuously monitors the contact force on the tensile testing machine indenter in real time using a high-precision mechanical sensor fixed above the indenter.

[0029] In order to eliminate the interference caused by the background high-frequency vibration of the mechanical transmission device during operation on the determination of mechanical state, this embodiment performs a smoothing and noise reduction data processing process on the mechanical simulation electrical signal acquired in real time by the high-precision mechanical sensor.

[0030] The specific implementation process is as follows: In this embodiment, analog electrical signals are continuously acquired at a fixed sampling frequency of 1000 Hz and converted into discrete digital mechanical sequences. Then, a moving average window algorithm is used to smooth the digital mechanical sequences. The window length parameter of the moving average window algorithm is set to 50 consecutive sampling points. The function of this parameter is to accurately filter out environmental mechanical noise frequencies above 20 Hz. The single stable feedback value output after smoothing calculation is used as the true effective value of the contact force used in this embodiment to determine the contact state.

[0031] As the lower end face of the tensile testing machine indenter makes substantial physical contact with the tip of the isolated lens, the noise-reduced contact force exhibits a monotonous upward trend from zero. The underlying control logic of this embodiment continuously compares the currently acquired contact force with a preset contact force threshold. The preset contact force threshold is the minute critical force required for the tensile testing machine indenter to just completely adhere to the slippery biological soft tissue surface, displacing the surface-adhered tissue fluid without causing macroscopic plastic deformation of the lens. This threshold value is derived from preliminary statistical results of the apparent tension of isolated lenses from a large number of small animals of the same species. In this embodiment, the preset contact force threshold is strictly set to 0.02 Newtons. The instant the monitored contact force precisely reaches 0.02 Newtons, this embodiment immediately triggers a hardware interrupt command to the drive motor, stopping the movement of the tensile testing machine indenter and recording the monitored contact force at that moment as the preload, thus characterizing the initial compression state of the testing system.

[0032] With the tensile testing machine indenter in a state of absolute physical stillness and maintaining the preload, this embodiment performs a zero-point calibration operation to reset the coordinate system and mechanical baseline. This embodiment reads the current absolute grating ruler encoding value of the tensile testing machine displacement measurement system, forcibly maps this grating ruler encoding value in the software measurement logic, and sets it as the absolute zero point of the displacement measurement system.

[0033] Simultaneously, this embodiment sends a hardware electronic zeroing command to the differential amplifier inside the measurement system, forcibly subtracting and zeroing the current comprehensive mechanical reading, which includes the preload and the base bias force such as the weight of the sensor's own tooling, thereby defining the force state as the mechanical zero point for subsequent application of formal test loads.

[0034] After completing the aforementioned dual physical zeroing operations of geometry and mechanics, this embodiment further performs a 3-second static stability verification data processing procedure to ensure the absolute reliability of the calibration results. During the static stability verification data processing, this embodiment continuously collects displacement fluctuation values ​​and mechanical fluctuation values ​​after zeroing. This embodiment calculates the maximum range of displacement and mechanical fluctuation values ​​respectively. When it is determined that the range of displacement fluctuation values ​​is strictly within the hardware tolerance band of 0.002 mm and the range of mechanical fluctuation values ​​is strictly within the hardware tolerance band of 0.005 Newtons within a continuous 3-second interval, this embodiment determines that the internal stress of the system has been released and the electronic signal baseline has reached a steady state. At this point, this embodiment confirms that the interference of system dummy position and contact gap has been successfully eliminated, and accurate initial test boundary conditions have been established to finally complete the zero-point calibration.

[0035] Furthermore, the specific implementation process of steps 300-400 is as follows: In this embodiment, after completing the pre-calibration, the process proceeds to control the tensile testing machine to vertically compress the isolated lens at a preset speed and collect the original load-displacement data in real time.

[0036] First, in this embodiment, the initial thickness parameter of the isolated lens is obtained using a high-precision optical micrometer with a paraxial orientation. This initial thickness parameter characterizes the maximum absolute span of the sagittal axis of the lens under natural, uncompressed conditions; in this embodiment, this parameter is specifically measured to be 4.0 mm. To obtain sufficient elastic characteristic response while avoiding excessive compression that could cause irreversible physical breakage of the fibers within the biological soft tissue, this embodiment sets a target compression displacement based on the obtained initial thickness parameter.

[0037] Specifically, in this embodiment, the control boundary of the target compression displacement is strictly limited to 20% of the initial thickness parameter, that is, the target compression displacement is calculated and fixed to be 0.80 mm.

[0038] After setting the aforementioned displacement boundary, this embodiment controls the servo motor of the tensile testing machine to drive the indenter to uniformly and vertically press down on the isolated lens at the preset speed. The preset speed is set to an extremely low quasi-static loading rate, specifically 0.05 mm / s. This constant rate effectively releases the viscous dissipation caused by the extremely high water content within the lens, ensuring that the measured mechanical response closely approximates its true elastic properties. Throughout the entire dynamic process of the indenter continuously pressing down until the actual displacement precisely reaches the set target compression displacement of 0.80 mm, the data acquisition card in this embodiment synchronously records the corresponding instantaneous load and instantaneous displacement values ​​according to a preset sampling frequency. This embodiment sets the preset sampling frequency to 100 Hz, meaning that a pair of physical quantity readings is extracted every 0.01 seconds. High-frequency dense sampling generates and outputs the original load-displacement data, which consists of a large number of discrete data point pairs.

[0039] After acquiring the raw load-displacement data, this embodiment immediately enters the digital filtering operation stage for denoising the raw load-displacement data. First, the acquired raw load-displacement data is separated and decoupled in the system cache, accurately extracting independent raw load sequences and independent raw displacement sequences. Considering that the ball screw rotation and motor driver of the tensile testing machine introduce high-frequency mechanical vibration noise to the test interface, this embodiment uses a moving average filtering algorithm to perform forced smoothing filtering on the separated raw load sequences. During this operation, the step size of the sliding window is precisely set to 15 data points. The force curve is reconstructed by calculating the local arithmetic mean point by point along the time axis, thoroughly filtering out background vibration interference with frequencies higher than 5 Hz, thereby obtaining a smooth and monotonically increasing smooth load sequence. Subsequently, this embodiment re-pairs and combines the obtained smooth load sequence with the raw displacement sequence (with no time delay difference) based on the same timestamp, packaging and outputting the denoised raw load-displacement data after eliminating hardware noise interference.

[0040] Next, this embodiment performs spatial dimension derivative calculations on the denoised original load-displacement data. Its core purpose is to mathematically isolate the nonlinear surface contact segment caused by irregular morphology in the initial testing phase. In the discrete data domain, this embodiment uses a difference algorithm to calculate the local derivative values ​​between adjacent data points in the denoised original load-displacement data. Specifically, it divides a small load increment by a small displacement increment to generate a full-process derivative sequence characterizing the transient stiffness evolution of the sample. To quantitatively evaluate the stability of this transient stiffness, this embodiment forcibly nests an evaluation sliding window within the generated full-process derivative sequence. The width of the sliding window is preset to contain 50 consecutive derivative values. This embodiment progressively shifts the sliding window along the direction of displacement increase and calculates the statistical variance of all local derivative values ​​within the sliding window in real time. This value is used as the sole criterion for characterizing the true linearity of the mechanical curve.

[0041] During the variance step-by-step sliding window calculation, this embodiment continuously compares the current variance with a preset fluctuation threshold and simultaneously monitors the corresponding window displacement span. The preset fluctuation threshold characterizes the maximum allowable self-fluctuation amplitude of material stiffness when the isolated lens enters the stable elastic deformation stage; this embodiment strictly sets it to a minimum value of 0.001. Simultaneously, to exclude extremely short, accidental linear segments caused by local structural defects, this embodiment sets a preset effective interval length of 0.15 mm as the baseline tolerance standard. This embodiment triggers a positive judgment command only when the variance calculated in this embodiment is consistently below 0.001, and the actual displacement span continuously covered by this low variance state is greater than 0.15 mm, confirming that the continuous data interval swept by the current sliding window is the continuous linear response segment. Finally, this embodiment accurately extracts all corresponding load and displacement data located within the determined continuous linear response segment from the denoised original load-displacement data, truncates and automatically discards redundant data in the front nonlinear compaction zone and the rear nonlinear yield failure zone, and solidifies and outputs them as the target load-displacement data, providing pure and absolutely reliable linear material for subsequent high-precision elastic calculation.

[0042] Furthermore, the specific implementation process of step 500 is as follows: In this embodiment, after acquiring the target load-displacement data, a linear regression fitting algorithm based on the least squares method is used to fit and extract the slope of the target load-displacement data. This embodiment uses all discrete data points within the continuous linear response segment determined in the aforementioned steps as the basis for calculation. At a fixed sampling frequency of 100 Hz, the number of valid data points input for calculation in this embodiment is specifically 150. The instantaneous displacement value collected in real-time by the tensile testing machine is used as the displacement independent variable, and the corresponding instantaneous load value synchronously output by the high-precision sensor is used as the load dependent variable. This embodiment uses the least squares algorithm to find a regression line that minimizes the sum of the squares of the distances from the aforementioned 150 discrete data points to the theoretical line, thereby completing the numerical solution process of the univariate linear regression analysis and constructing a linear fitting equation describing the initial compression state of the lens.

[0043] In constructing the linear fitting equation, this embodiment defines a precise algebraic mapping relationship to eliminate system and environmental errors. Specifically, this embodiment quantifies the instantaneous load value as: the extracted characteristic slope of the load-displacement curve multiplied by the effective displacement increment, and then superimposed with the initial surface tension baseline constant caused by the tissue fluid on the lens surface. This embodiment directly establishes the extracted characteristic slope of the load-displacement curve as the initial stiffness to characterize the lens's ability to resist initial deformation. The effective displacement increment is the actual deformation difference after deducting the flexibility compensation coefficient of the test system from the instantaneous displacement value. The flexibility compensation coefficient of the test system is derived from a pre-conducted standard rigid steel ball compression calibration experiment, used to accurately eliminate the background mechanical deformation of the tensile testing machine frame under stress. In this embodiment, it is strictly set to 0.005 mm. The initial surface tension baseline constant is derived from a pre-conducted unloaded saline droplet tensile test, used to peel off the interference of wet synovial film adhesion on the actual physical force. In this embodiment, its calibration value is set to 0.002 Newtons.

[0044] To transform the one-dimensional initial stiffness into a parameter that can realistically characterize the material properties in three-dimensional space, this embodiment inputs the established initial stiffness into a preset elasticity equation for spatial solution. Before performing the elasticity equation solution, this embodiment first calculates the equivalent contact curvature radius based on the characteristic size constant of the isolated lens. In this embodiment, the initial equatorial plane radius of the isolated lens is measured and precisely set to 2.5 mm using a high-precision binocular vision system before the lens is placed into the base; simultaneously, the CNC machining design parameters for the concave surface curvature radius of the dedicated base support groove are retrieved and fixed at 3.0 mm. In this embodiment, the product of the two radius values ​​is used as the dividend, and the difference between the concave surface curvature radius and the initial equatorial plane radius is used as the divisor. The quotient obtained by dividing the two is the calculated equivalent contact curvature radius, which quantifies the actual geometric interference between the spherical soft tissue and the concave rigid groove.

[0045] After obtaining the equivalent contact curvature radius, this embodiment formally performs the underlying algebraic operations of the elasticity equation to solve for the apparent elastic coefficient. The underlying calculation logic of the elasticity equation is based on Hertzian contact mechanics theory, which assumes the lens to be incompressible biological soft tissue. The specific numerical calculation process is strictly fixed as follows: In this embodiment, the dimensionless mechanical constant Arabic numeral 9 is multiplied by the previously established initial stiffness to obtain the numerator value; simultaneously, this embodiment performs a square root operation on the previously calculated equivalent contact curvature radius to obtain the square root of curvature, and multiplies the geometric constant Arabic numeral 16 derived based on boundary conditions with the square root of curvature to obtain the denominator value. In this embodiment, the obtained numerator value is divided by the obtained denominator value, and the final result of the calculation is the apparent elastic coefficient, thereby completely eliminating the physical interference caused by the difference in the morphology of the base pit contact surface at the algebraic level.

[0046] Based on the output of the apparent elasticity coefficient, this embodiment further utilizes the aforementioned constructed linear fitting equation to perform inverse prediction and forward mapping calculations to obtain the load corresponding to the specific displacement and the compression amount corresponding to the specific load. In specific implementation, this embodiment substitutes the standardized deformation baseline used for lateral comparison in medical terms, i.e., a specific displacement value of 0.40 mm, into the displacement independent variable position of the linear fitting equation to calculate the load corresponding to the specific displacement borne by the lens sample at this time. Similarly, this embodiment substitutes the critical force value characterizing the early warning of lens capsule tissue yielding failure, i.e., a specific load value of 0.05 Newtons, into the load dependent variable position of the linear fitting equation, and solves inversely using the algebraic equation rearrangement rule to obtain the compression amount corresponding to the specific load. Thus, this embodiment completes the rigorous calculation and functional application closed loop for all lens elasticity-related parameters.

[0047] Specifically, the calculation expression for the linear fitting equation is as follows: ; In the formula, This represents the instantaneous load value acquired in real time. This represents the corresponding instantaneous displacement value. This represents the slope of the extracted load-displacement curve, i.e., the initial stiffness. This represents the compliance compensation coefficient of the test system. This represents the baseline constant of the initial surface tension caused by the tissue fluid on the lens surface; The calculation expression for the elasticity equation is as follows: ; in, The calculation expression is: ; In the formula, This represents the apparent elasticity coefficient. Indicates the equivalent contact curvature radius. This represents the initial equatorial radius of the isolated lens. The radius of curvature of the concave surface of the dedicated base support groove is indicated, and satisfies the following conditions: .

[0048] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0049] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A special base for testing the elasticity of the lens of small animals using a tensile testing machine, characterized in that, include: The base body is fixed to the sample stage of the tensile testing machine; A lens support portion is disposed on the base body. The lens support portion has an upwardly opening support groove. The inner surface of the support groove has a concave structure that adapts to the shape of the lens to be tested, and is used to accommodate the lower half of the lens to be tested and to initially position the lens to be tested. A limiting structure is provided in the outer edge region of the support groove to limit the lateral displacement of the lens under test during the pressure test, so as to reduce lateral slippage.

2. A special base for testing the elasticity of the lens of small animals using a tensile testing machine, as described in claim 1, is characterized in that... The inner surface of the support groove is provided with a flexible contact layer; The flexible contact layer is any one of a silicone layer, an elastic membrane, and a hydrogel layer; The flexible contact layer is used to improve the contact state between the lens under test and the dedicated base, so as to reduce the local stress concentration of the lens under test during the pressure test.

3. An analytical method for testing the elasticity of the lens of small animals using a tensile testing machine, applied to the dedicated base as described in any one of claims 1-2, characterized in that, The analytical method includes: Place the isolated lens to be tested in the support groove of the special base, so that the center of the isolated lens is located on the loading axis of the tensile testing machine head; Adjust the initial position of the tensile testing machine indenter and perform preload or zero-point calibration; The tensile testing machine is controlled to vertically compress the isolated lens at a preset speed, and the original load-displacement data is collected in real time. The original load-displacement data is denoised, and the derivative of the denoised original load-displacement data is calculated to automatically identify and extract continuous linear response segments where the derivative value fluctuation is less than a preset fluctuation threshold, so as to obtain the target load-displacement data. A linear regression fitting algorithm was used to fit the target load-displacement data and extract the slope, and the elasticity-related parameters of the lens were calculated. The lens elasticity parameters include: initial stiffness, apparent elastic coefficient, load corresponding to a specific displacement, compression corresponding to a specific load, and characteristic slope of the load-displacement curve.

4. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, The isolated lens to be tested is placed in the support groove of the dedicated base, so that the center of the isolated lens is located on the loading axis of the tensile testing machine indenter, including: The isolated lens to be tested is placed into the support groove of the special base; The concave shape of the support groove is used to adaptively center the inserted isolated lens to be tested, so as to establish the initial physical centering state. The pressure head of the tensile testing machine is controlled to descend to a preset observation height, and the horizontal position of the dedicated base is finely adjusted according to the initial physical alignment state to confirm that the vertex of the isolated lens to be tested is strictly aligned with the loading axis of the pressure head of the tensile testing machine.

5. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, Adjusting the initial position of the tensile testing machine indenter and performing preload or zero-point calibration includes: The tensile testing machine indenter is controlled to approach the excised lens at a preset calibration speed, and the contact force on the tensile testing machine indenter is monitored in real time. When the detected contact force reaches the preset contact force threshold, the movement of the tensile testing machine head is stopped, and the detected contact force at this time is recorded as the preload; The initial position of the tensile testing machine head, which is recorded with the preload, is set as the absolute zero point of the displacement measurement system, and the reading of the contact force sensor is reset to zero to complete the zero-point calibration.

6. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, The tensile testing machine is controlled to vertically compress the extracted lens at a preset speed, and raw load-displacement data is collected in real time, including: Obtain the initial thickness parameters of the isolated lens, and set the target compression displacement based on the obtained initial thickness parameters; The tensile testing machine is controlled to apply uniform vertical downward pressure to the isolated lens at the preset speed until the actual vertical displacement reaches the set target compression displacement. During the process of uniformly pressing down vertically on the isolated lens, the corresponding instantaneous load value and instantaneous displacement value are recorded synchronously according to the preset sampling frequency to obtain the original load-displacement data.

7. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, The original load-displacement data is denoised, including: The original load sequence and the original displacement sequence are separated from the collected original load-displacement data; The original load sequence was smoothed by using a moving average filtering algorithm to remove high-frequency mechanical vibration noise during the test, resulting in a smoothed load sequence. The obtained smoothed load sequence is re-paired and combined with the separated original displacement sequence to obtain the original load-displacement data after denoising.

8. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, The derivative of the denoised original load-displacement data is calculated to automatically identify and extract continuous linear response segments where the derivative fluctuation is less than a preset fluctuation threshold, thus obtaining the target load-displacement data, including: Calculate the local derivative values ​​between adjacent data points in the denoised original load-displacement data to obtain the whole process derivative sequence; A sliding window is set in the generated full-process derivative sequence, and the variance of the local derivative values ​​within the sliding window is calculated step by step; When the calculated variance is consistently less than the preset fluctuation threshold and the corresponding displacement span is greater than the preset effective interval length, the interval swept by the current sliding window is determined to be the continuous linear response segment. From the denoised original load-displacement data, the corresponding load data and displacement data located within the determined continuous linear response segment are extracted to obtain the target load-displacement data.

9. The analytical method for testing the elasticity of the lens of small animals using a tensile testing machine as described in claim 3, characterized in that, A linear regression fitting algorithm was used to fit and extract the slope of the target load-displacement data, and the elasticity-related parameters of the lens were calculated, including: The linear regression fitting algorithm based on the least squares method performs univariate linear regression analysis on the displacement independent variable and load dependent variable in the acquired target load-displacement data to construct a linear fitting equation. Extract the slope coefficients of the constructed linear fitting equation, use the extracted slope coefficients as the characteristic slope of the load-displacement curve, and establish the initial stiffness based on the characteristic slope of the load-displacement curve. The established initial stiffness is input into the preset elasticity equation, and the solution is performed according to the characteristic size constant of the isolated lens to obtain the apparent elastic coefficient, the load corresponding to the specific displacement, and the compression corresponding to the specific load. The calculation expression for the linear fitting equation is as follows: ； In the formula, This represents the instantaneous load value acquired in real time. This represents the corresponding instantaneous displacement value. This represents the slope of the extracted load-displacement curve, i.e., the initial stiffness. This represents the compliance compensation coefficient of the test system. This represents the baseline constant of the initial surface tension caused by the tissue fluid on the lens surface; The calculation expression for the elasticity equation is as follows: in, The calculation expression is: In the formula, This represents the apparent elasticity coefficient. Indicates the equivalent contact curvature radius. This represents the initial equatorial radius of the isolated lens. The radius of curvature of the concave surface of the dedicated base support groove is indicated, and satisfies the following conditions: .

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