Measurement method, instrument, electronic device, and program product for corneal topography

Abstract

The application belongs to the technical field of ophthalmic medical instruments, and provides a corneal topography measurement method, an instrument, an electronic device and a program product, the corneal topography measurement method obtains the corneal diameter and the corneal vertex of the eye cornea of a detected object; determines the distance between the corneal vertex and the vertex of a Placido disc, determines the eccentricity of the Placido disc; determines the shape of the Placido disc according to the eccentricity of the Placido disc, and determines the ring number of the Placido disc according to the corneal diameter; collects the corneal topography imaging after the concentric ring on the Placido disc is reflected on the corneal surface of the detected object; based on the shape and the ring number of the Placido disc, analyzes a plurality of concentric rings contained in the corneal topography imaging, and obtains the corneal topography data of the detected object. The accuracy of measuring the corneal topography is improved, so that the micro-landscape features of the corneal surface can be more accurately obtained.

Description

Technical Field

[0001] This application belongs to the field of ophthalmic medical device technology, and more specifically, relates to a method, instrument, electronic device and program product for measuring corneal topography. Background Technology

[0002] The cornea accounts for 80% of the total refractive power of the eyeball, and even minor changes in the surface morphology of the cornea can affect the visual function of the entire eye. Corneal topography is a commonly used method to describe the local topography of the corneal surface. It can reflect the morphology of various points on the corneal surface, and based on the corneal topography, the radius of curvature of various points on the cornea can be determined, as well as the overall changes on the corneal surface can be assessed.

[0003] A corneal topography instrument is a device used to detect corneal topography. Currently, the most widely used is the Placido disc-based corneal topography instrument. It works by forming concentric rings of alternating light and dark light on the surface of the cornea. A CCD camera captures images of these corneal reflection rings and transmits them to a host computer for image processing software to perform image processing and data analysis.

[0004] However, existing methods for measuring corneal topography have low accuracy and cannot accurately capture the minute morphological features of the corneal surface. Summary of the Invention

[0005] The purpose of this application is to provide a method, instrument, electronic device, and program product for measuring corneal topography, aiming to solve the technical problem that existing methods and systems for measuring corneal topography have low accuracy and cannot accurately capture the minute morphological features of the corneal surface.

[0006] To achieve the above objectives, according to the first aspect of this application, a method for measuring corneal topography is provided, the method comprising:

[0007] Obtain the corneal diameter and corneal vertex of the object being tested;

[0008] Determine the distance between the corneal apex and the apex of the Placido disc, and determine the eccentricity of the Placido disc;

[0009] The shape of the placido disc is determined based on the eccentricity of the placido disc, and the number of rings of the placido disc is determined based on the corneal diameter;

[0010] The concentric rings on the Placido disk are used to acquire corneal topography images after reflection from the corneal surface of the object being tested;

[0011] Based on the shape and number of rings of the Placido disk, the corneal topography data of the tested object is obtained by analyzing the multiple concentric rings contained in the corneal topography imaging.

[0012] Optionally, in one possible implementation of the first aspect, determining the distance between the corneal apex and the apex of the placido disk, and determining the eccentricity of the placido disk, includes:

[0013] Determine the distance between the corneal vertex and the vertex of the plascido disk to be designed, as well as the object distance between the plascido disk and the optical imaging camera;

[0014] Based on the distance and object distance, the sagitta of each ring of the Placido disk is determined, wherein the Placido disk comprises multiple independent concentric rings;

[0015] The eccentricity of the Plassid disk is determined based on the sagitta of each ring of the Plassid disk, the radius of curvature of the vertex of the Plassid disk, and the radius of each ring of the Plassid disk.

[0016] Optionally, in one possible implementation of the first aspect, determining the shape of the plascido disk based on its eccentricity includes:

[0017] If the eccentricity of the Plassido disk is zero, then the shape of the Plassido disk is determined to be spherical, wherein when the Plassido disk is spherical, concentric rings in the Plassido disk are distributed on the surface of the Plassido disk;

[0018] If the eccentricity of the Plassid disk is greater than zero and less than a predetermined value, then the shape of the Plassid disk is determined to be conical, wherein when the Plassid disk is conical, the concentric rings in the Plassid disk are distributed on the side of the Plassid disk.

[0019] Optionally, in one possible implementation of the first aspect, determining the number of rings of the Placido disc based on the corneal diameter includes:

[0020] Compare the corneal diameter with a predetermined diameter threshold;

[0021] If the comparison result indicates that the corneal diameter is greater than or equal to the diameter threshold, then the number of rings of the Placidor disc is determined to be the first value;

[0022] If the comparison result indicates that the corneal diameter is less than the diameter threshold, then the number of rings of the Placidor disc is determined to be a second value, wherein the first value is greater than the second value.

[0023] Optionally, in one possible implementation of the first aspect, before analyzing the multiple concentric rings contained in the corneal topography image based on the shape and number of rings of the Plassid disk to obtain the corneal topography data of the object being tested, the method further includes:

[0024] The imaging magnification of the corneal topography image is determined based on the corneal diameter.

[0025] By using different lens combinations and depending on the imaging magnification, corneal topographic imaging can be magnified or reduced.

[0026] Optionally, in one possible implementation of the first aspect, the step of analyzing multiple concentric rings contained in the corneal topography image based on the shape and number of rings of the Plassid disk to obtain corneal topography data of the object being tested includes:

[0027] Obtain the shape and number of concentric rings contained in the corneal topography image;

[0028] Based on the shape and number of rings of the Placido disk, the shape and number of rings of multiple concentric rings contained in the corneal topography imaging are analyzed to obtain the numerical value of the spacing variation of the multiple concentric rings of the Placido disk in the corneal topography imaging.

[0029] The corneal curvature radius of the tested object is determined based on the value of the spacing change.

[0030] According to a second aspect of this application, a corneal topography measuring instrument is provided, comprising:

[0031] Placido disc;

[0032] The host computer is used to acquire the corneal diameter and corneal vertex of the cornea of ​​the object being tested; determine the distance between the corneal vertex and the vertex of the Placido disk; determine the eccentricity of the Placido disk; determine the shape of the Placido disk based on the eccentricity of the Placido disk; and determine the number of rings of the Placido disk based on the corneal diameter.

[0033] An optical imaging camera is used to acquire corneal topography images after the concentric rings on the Placido disk are reflected on the corneal surface of the object being tested;

[0034] The host computer is also used to analyze multiple concentric rings contained in the corneal topography imaging based on the shape and number of rings of the Plassid disk, and obtain the corneal topography data of the object being detected.

[0035] Optionally, in one possible implementation of the second aspect, the measuring instrument for the corneal topography further includes:

[0036] The object-side telecentric system is used to determine the imaging magnification of the corneal topography image based on the corneal diameter; and to perform magnification or reduction processing on the corneal topography image based on the imaging magnification using different lens combinations.

[0037] Optionally, in one possible implementation of the second aspect, the object-centric telecentric system includes:

[0038] The aperture stop, the front lens and the rear lens of the object-side telecentric lens, wherein:

[0039] Both the front lens and the rear lens are achromatic lenses;

[0040] The aperture of the aperture is set to 3-7mm.

[0041] Optionally, in one possible implementation of the second aspect, the measuring instrument for the corneal topography further includes:

[0042] An illumination unit is used to provide an illumination source during corneal imaging;

[0043] A bandpass filter is placed in the optical path in front of the optical imaging camera, and the bandpass filtering of the bandpass filter is set to correspond to the wavelength of the illumination source.

[0044] The second aspect and any implementation thereof correspond to the first aspect and any implementation thereof, respectively. The technical effects of the second aspect and any implementation thereof can be found in the technical effects of the first aspect and any implementation thereof, as described above, and will not be repeated here.

[0045] According to a third aspect of this application, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the electronic device causes the electronic device to perform the method as described in any one of the claims.

[0046] According to a fourth aspect of this application, a computer-readable storage medium is provided that stores a computer program, which, when executed by a processor, implements the method as described in any one of the claims.

[0047] According to a fifth aspect of this application, a computer program product is provided that, when run on an electronic device, causes the electronic device to perform the method described in any one of the first aspects above.

[0048] It is understandable that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0049] The measurement method of this application obtains the corneal diameter and corneal apex, then determines the distance between the corneal apex and the apex of the plascidosity disk, as well as the eccentricity of the plascidosity disk. Based on the eccentricity, the shape of the plascidosity disk is determined, and the number of rings on the plascidosity disk is determined based on the corneal diameter. This allows for a precise fit between the plascidosity disk and the cornea being tested. For example, a plascidosity disk with an appropriate number of rings can be selected for corneas of different sizes, and a plascidosity disk with an appropriate shape can be selected for corneas with different curvature characteristics. This ensures that the concentric rings formed on the corneal surface more accurately reflect the corneal morphology, improving measurement accuracy.

[0050] Subsequently, by capturing images of the concentric rings of a precisely fitted Placido disc reflected off the corneal surface, the resulting images more accurately reflect the true morphology of the cornea. Further analysis of the concentric rings in the images, based on the shape and number of rings of the Placido disc, allows for a more accurate reflection of the radius of curvature at various points on the cornea and the overall changes in the corneal surface. For example, when analyzing changes in the spacing between the concentric rings to determine the corneal radius of curvature, the precise fit between the Placido disc and the cornea allows for a more accurate calculation of the radius of curvature, effectively improving the accuracy of corneal topography measurements and accurately capturing minute morphological features of the corneal surface. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic flowchart of a method for measuring corneal topography provided in an embodiment of this application;

[0053] Figure 2 This is a schematic flowchart of an optional corneal topography measurement method provided in an embodiment of this application;

[0054] Figure 3 This is a schematic flowchart of an optional corneal topography measurement method provided in an embodiment of this application;

[0055] Figure 4 This is a schematic flowchart of an optional corneal topography measurement method provided in an embodiment of this application;

[0056] Figure 5aThis is another embodiment of the optional corneal topography provided in this application. Figure 3 A schematic diagram of the D model;

[0057] Figure 5b This is a schematic diagram of an optional corneal topography image obtained by using two-color 3D printing technology, provided in another embodiment of this application;

[0058] Figure 6 This is a schematic diagram of the structure of a corneal topography measuring instrument provided in an embodiment of this application;

[0059] Figure 7 This is a schematic diagram of the structure of an optional corneal topography measuring instrument provided in an embodiment of this application;

[0060] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0061] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0062] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0063] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0064] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0065] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0066] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0067] First, some terms used in the embodiments of this application will be explained to facilitate understanding by those skilled in the art.

[0068] The Placido disc, also known as the Placido disk, is a disc-shaped device with concentric rings. When the Placido disc is placed in front of the subject's eyes, the shape of the cornea is assessed by observing the reflected image of the concentric rings on the corneal surface.

[0069] The above is a brief introduction to the terms used in the embodiments of this application, and will not be repeated below.

[0070] The cornea accounts for 80% of the total refractive power of the eyeball, and even minor changes in the surface morphology of the cornea can affect the visual function of the entire eye. Corneal topography is a commonly used method to describe the local topography of the corneal surface. It can reflect the morphology of various points on the corneal surface, and based on the corneal topography, the radius of curvature of various points on the cornea can be determined, as well as the overall changes on the corneal surface can be assessed.

[0071] A corneal topography instrument is a medical examination instrument used to measure the surface morphology of the human cornea. It provides a wealth of information for clinical medical applications and can be used to diagnose conditions such as keratoconus, corneal astigmatism, peripheral corneal degeneration, and corneal morphological changes caused by contact lenses. It can also be used to observe changes in corneal morphology and curvature before and after various corneal surgeries, such as corneal transplantation, surface keratomileusis, radial keratotomy, and laser refractive keratotomy.

[0072] A corneal topography instrument is a device used to detect corneal topography. Currently, the most widely used is the Placido disc-based corneal topography instrument. It works by forming concentric rings of alternating light and dark light on the surface of the cornea. A CCD camera captures images of these corneal reflection rings and transmits them to a host computer for image processing software to perform image processing and data analysis.

[0073] However, existing methods and systems for measuring corneal topography have low accuracy and cannot accurately capture the minute morphological features of the corneal surface.

[0074] This application provides an example of a method for measuring corneal topography; please refer to... Figure 1 As shown, Figure 1 A schematic flowchart of a corneal topography measurement method provided in this application is shown. This is by way of example and not limitation; the method can be applied to or run in electronic devices. The method includes:

[0075] S101, Obtain the corneal diameter and corneal vertex of the object being tested.

[0076] S102, determine the distance between the corneal apex and the apex of the Placido disc, and determine the eccentricity of the Placido disc.

[0077] S103, the shape of the plascidus is determined based on the eccentricity of the plascidus, and the number of rings of the plascidus is determined based on the corneal diameter.

[0078] S104, acquires corneal topography images after the concentric rings on the Placidor disc are reflected on the corneal surface of the object being tested.

[0079] S105, based on the shape and number of rings of the Plassid disk, analyzes multiple concentric rings contained in the corneal topography imaging to obtain the corneal topography data of the tested object.

[0080] In this embodiment of the application, in the corneal topography measurement scenario, the object being detected can be a human, an animal (such as a cat, a dog, a bird, a fish, etc.).

[0081] It should be understood that the corneal diameter can be used to determine parameters such as the number of rings of the Placido disc (also known as the Placido disk) and the lens combination of the 4F object-side telecentric system, while the corneal apex is an important reference point for subsequent calculations of geometric relationships and imaging.

[0082] In specific implementation methods, the corneal diameter can be obtained using specialized corneal measurement tools, such as a keratometer or an optically based measuring instrument, by measuring the maximum span of the cornea in the horizontal or vertical direction. The corneal apex can be determined using the instrument's positioning system, with the subject's eye in an appropriate position, based on the anatomical features of the eye and the coordinate system of the optical measurement system.

[0083] The distance between the corneal apex and the Placido disk apex is crucial for calculating geometric parameters such as object distance, image distance, and corneal curvature. The eccentricity of the Placido disk determines its shape, which in turn affects the distribution of concentric rings and subsequent imaging results.

[0084] In specific implementations, precise scale markings can be set in the optical measurement system (CCD camera) or a distance sensor can be used to measure the straight-line distance between the vertices of the Placido disk and the cornea of ​​the object being tested when the Placido disk is aligned with the cornea of ​​the object being tested. The eccentricity can be measured and determined based on the characteristics of the cornea of ​​the object being tested and the system's preset rules. Different eccentricities correspond to different shapes of the Placido disk; a suitable shape and number of rings can better cover the corneal surface, providing conditions for accurate corneal topography measurement. For example, when the eccentricity e = 0, the shape of the Placido disk is determined to be spherical (Placidoring); when the eccentricity 0 < e < 1, the shape of the Placido disk is determined to be conical (Placidoring). The number of rings of the Placido disk is selected according to the corneal diameter. For example, a 16-ring Placido disk can be used for species with smaller corneal diameters (such as chickens or mice), while a 32- or 36-ring Placido disk can be used for species with larger corneal diameters (such as humans or rabbits).

[0085] Acquiring the corneal reflection of the concentric rings of the Placido disk is the primary image source for subsequent analysis of corneal topography data. First, the Placido disk is illuminated using a suitable illumination unit (such as a flexible LED) to ensure a clear reflection of the concentric rings on the corneal surface. Then, the reflection image is acquired using an optical measurement system. During acquisition, the 4F object-side telecentric system needs to be adjusted to ensure clear imaging and proper scale. Simultaneously, a bandpass filter filters out stray light, ensuring that the optical measurement system acquires only the useful light signal from the concentric rings of the Placido disk.

[0086] Analyzing acquired corneal topographic images yields topographic data such as curvature and height at various points on the corneal surface, enabling assessment of corneal health and guidance for clinical treatment. Specific implementation methods include, but are not limited to: preprocessing the acquired images, such as using image processing software for noise reduction and contrast enhancement; then using edge detection algorithms (such as the Canny algorithm) to extract the edges of concentric rings, counting the number of rings, and calculating parameters such as the corneal radius of curvature using geometric optics principles and formulas. For example, based on changes in the spacing and reflection positions of the concentric rings, combined with known parameters such as the shape, number of rings, object distance, and image distance of the Placido disk, the curvature at various points on the cornea can be calculated. For deformed concentric rings (representing irregularities on the corneal surface), local anomalies can be analyzed by comparing the corneal topographic image with an ideal image corresponding to a standard Placido disk shape and number of rings.

[0087] The aforementioned method for measuring corneal topography improves the accuracy and efficiency of measurements. The shape of the Placido disk is determined based on its eccentricity, and the number of rings is determined based on the corneal diameter, allowing for the calculation and design of Placido disks suitable for different corneal sizes. Furthermore, the Placido disk contains multiple independent concentric black rings to form a pattern of alternating light and dark concentric rings on the corneal surface. Placido is processed using dual-color 3D technology, achieving a good combination of the two color materials to meet design requirements, making the diagnosis and treatment of corneal diseases more accurate and reliable.

[0088] The measurement method of this application obtains the corneal diameter and corneal apex, then determines the distance between the corneal apex and the apex of the plascidosity disk, as well as the eccentricity of the plascidosity disk. Based on the eccentricity, the shape of the plascidosity disk is determined, and the number of rings on the plascidosity disk is determined based on the corneal diameter. This allows for a precise fit between the plascidosity disk and the cornea being tested. For example, a plascidosity disk with an appropriate number of rings can be selected for corneas of different sizes, and a plascidosity disk with an appropriate shape can be selected for corneas with different curvature characteristics. This ensures that the concentric rings formed on the corneal surface more accurately reflect the corneal morphology, improving measurement accuracy.

[0089] Subsequently, by capturing images of the concentric rings of a precisely fitted Placido disc reflected off the corneal surface, the resulting images more accurately reflect the true morphology of the cornea. Further analysis of the concentric rings in the images, based on the shape and number of rings of the Placido disc, allows for a more accurate reflection of the radius of curvature at various points on the cornea and the overall changes in the corneal surface. For example, when analyzing changes in the spacing between the concentric rings to determine the corneal radius of curvature, the precise fit between the Placido disc and the cornea allows for a more accurate calculation of the radius of curvature, effectively improving the accuracy of corneal topography measurements and accurately capturing minute morphological features of the corneal surface.

[0090] It should be noted that the corneal topography measurement method and instrument are primarily applied in the field of ophthalmic medical device technology, particularly suitable for corneal disease examination, corneal morphology assessment before and after refractive surgery, detection of corneal diseases such as keratoconus, and measurement of corneal morphology during contact lens fitting. Because this application's example improves the accuracy of corneal topography while adapting to corneas of different diameters, it has broad application potential in the evaluation of corneal surgery and treatment.

[0091] It should be noted that in future application technologies, further optimization of the Placido disk's material selection and optical system configuration could expand its application scope to other technological fields related to precision surface measurement. For example, it could be modified for contact lens design, providing more precise corneal topography data to offer a better fit for personalized contact lenses. Furthermore, if the wavelength adaptability of the optical imaging system can be further improved, this invention could be applied to a wider range of biomedical imaging fields, providing technical support for other types of ocular imaging and non-contact surface measurement.

[0092] In one possible implementation, please refer to Figure 2 As shown, Figure 2 A schematic flowchart of an optional corneal topography measurement method provided in this application is shown, which determines the distance between the corneal apex and the apex of the Placido disk, and determines the eccentricity of the Placido disk, including:

[0093] S201, determine the distance between the corneal vertex and the vertex of the plascido disk to be designed, as well as the object distance between the plascido disk and the optical imaging camera;

[0094] S202, determine the sagitta of each ring of the Placido disk based on the distance and object distance, wherein the Placido disk contains multiple independent concentric rings;

[0095] S203. Determine the eccentricity of the Plassid disk based on the sagitta of each ring, the radius of curvature of the vertex of the Plassid disk, and the radius of each ring of the Plassid disk.

[0096] In practical measurement systems, the distance between the corneal apex and the plascidure disk apex can be obtained through precise mechanical positioning devices and distance sensors. For example, a high-precision displacement sensor can be installed at the relative position of the plascidure disk and the corneal measurement device, and the distance can be determined by measuring their relative displacement. The object distance can be determined based on the design parameters and calibration results of the optical imaging camera. For instance, when designing a 4F object-side telecentric system, the accurate object distance from the plascidure disk to the optical imaging camera (such as the front element of a 4F object-side telecentric lens) is determined based on parameters such as the lens focal length and position, combined with the system's installation and debugging.

[0097] According to the known distance L between the corneal vertex and the Placido disk vertex, where p is the object distance and z is the sagitta of each ring on the Placido disk, the relationship between the sagitta (in mm) of each ring on the Placido disk and the object distance (in mm) is:

[0098] z+p=L (1)

[0099] This formula is based on optical and geometric principles, and reflects the sagitta condition of each ring of the Placido disk under a specific positional relationship. When the distance L and the object distance p are known, substitute them into the above formula to perform calculation for each ring of the Placido disk. Since the Placido disk comprises a plurality of independent concentric rings, each ring is located at a different position, and the corresponding sagitta can be calculated according to this formula for all rings.

[0100] Let the radius (in mm) of each ring on the Placido disk be h, and the radius (in mm) of each ring of the image formed by reflection projected onto the cornea be h', then

[0101]

[0102] According to geometric optics, on the corneal image collected by the camera, the position data of each ring is the position of the virtual image formed by the cornea. This virtual image is not on the corneal surface, but is located at a distance behind the vertex of the corneal surface. The virtual image can be projected onto a plane, and according to the corneal characteristics of the detected object, the projected image is equally divided into n rings with equal spacing, the spacing between each ring is Δd, and the radius (in mm) of the innermost ring is h0, then:

[0103] h'=h0+(n-1)Δd (3)

[0104] Optionally, in a Placido corneal topography measurement system, the relationship between the sagitta z and the radius h of each ring of the Placido disk is:

[0105]

[0106] wherein e is the eccentricity of the Placido disk, and r0 is the vertex curvature radius (in mm) of the Placido disk. The eccentricity e of the Placido disk refers to the change rate of curvature from the central vertex to the edge of a curved surface. When e=0, the shape of the Placido disk is spherical, which is a Placido ring; when 0<e<1, the shape of the Placido disk is conical, which is a Placido cone.

[0107] In the corneal topography measurement system based on a Placido disk, the design formula of the Placido disk is:

[0108]

[0109] In one possible implementation, the shape of the plassid disk is determined based on its eccentricity, including:

[0110] If the eccentricity of the Plassid disk is zero, then the shape of the Plassid disk is determined to be spherical. When the Plassid disk is spherical, the concentric rings in the Plassid disk are distributed on the surface of the Plassid disk.

[0111] If the eccentricity of the Plassid disk is greater than zero and less than a predetermined value, then the shape of the Plassid disk is determined to be conical, wherein when the Plassid disk is conical, the concentric rings in the Plassid disk are distributed on the side of the Plassid disk.

[0112] In this application example, the determination of the shape of the Plassid disk based on eccentricity is set according to the principles of geometric optics and the requirements of corneal topography measurement. Eccentricity is a key parameter describing the shape of the Plassid disk. Determining the shape of the Plassid disk by setting different eccentricity ranges helps to accurately understand and utilize the role of the Plassid disk in corneal topography measurement.

[0113] When the eccentricity of the placido disk is zero, i.e., eccentricity e = 0, the shape of the placido disk is determined to be spherical. When the placido disk is spherical, its concentric rings are uniformly distributed across the entire surface. Geometrically, these concentric rings are centered on the center of the sphere, with each ring's plane at a different distance from the center but parallel to each other, and the center of each ring coincides with the center of the sphere. This distribution allows the concentric rings to reflect the curvature information of the corneal surface in a relatively regular form after reflection on the corneal surface during corneal topography. For example, if the corneal surface is an ideal sphere, the concentric rings reflected by the spherical placido disk will also exhibit a regular concentric distribution on the cornea. By analyzing the spacing and deformation of these rings, topographic data such as the radius of curvature of the cornea can be inferred.

[0114] When the eccentricity of the placido disk is greater than zero and less than a predetermined value (usually set to 1), i.e., eccentricity 0 < e < 1, the shape of the placido disk is determined to be conical. In a conical placido disk, concentric rings are distributed on the sides of the cone. The apex of the cone is the apex of the placido disk, and the concentric rings are radially distributed from the apex to the base along the sides of the cone. This structure is advantageous when measuring larger corneal diameters, as the wider distribution of the concentric rings better covers the corneal surface, thus obtaining more comprehensive corneal topographic information. For example, in cases with relatively large corneal diameters, such as the human eye, using a conical placido disk allows the reflection imaging of the concentric rings on the cornea to more fully reflect the topographic changes in the peripheral corneal region, aiding in the accurate diagnosis of peripheral corneal lesions or irregularities.

[0115] In practical corneal topography instruments, the shape of the Placido ring is typically defined as spherical when the eccentricity e = 0, and as conical when 0 < e < 1. It is important to note that regardless of the definition used in practical applications, the key is to ensure that the correspondence between the eccentricity and the shape of the Placido ring remains consistent throughout the measurement and analysis process to guarantee the accuracy and reliability of the measurement results.

[0116] In one possible implementation, please refer to Figure 3 As shown, Figure 3 A schematic flowchart of an optional corneal topography measurement method provided in this application is shown, which determines the number of rings of the Placido disc based on the corneal diameter, including:

[0117] S301, compare the corneal diameter with a predetermined diameter threshold;

[0118] S302, if the comparison result indicates that the corneal diameter is greater than or equal to the diameter threshold, then the number of rings of the Placido disc is determined as the first value;

[0119] S303, if the comparison result indicates that the corneal diameter is less than the diameter threshold, then the ring number of the Placidor disc is determined to be the second value, wherein the first value is greater than the second value.

[0120] Based on the principle of matching corneal size with the number of Placido disc rings, the number of Placido disc rings is determined according to the corneal diameter. Different corneal sizes require different numbers of concentric rings to accurately measure the corneal surface topography. By setting a diameter threshold, the corneal diameter is divided into two ranges. By comparing the corneal diameter with this diameter threshold, an appropriate number of Placido disc rings can be selected to ensure the accuracy and effectiveness of the measurement.

[0121] In a practical measurement system, after obtaining the corneal diameter of the object being tested, the measured corneal diameter is compared with a pre-set diameter threshold. If the comparison result shows that the corneal diameter is greater than or equal to the diameter threshold, it indicates that the cornea is relatively large, and the number of rings of the Placido disc is determined as the first value. For example, in the measurement of larger corneas such as the human eye, the diameter threshold may be set to 10 mm. When the measured corneal diameter is greater than or equal to 10 mm, the number of rings of the Placido disc is determined to be 32 rings (here, 32 rings is only a hypothetical first value example). It should be understood that a larger number of rings can more meticulously cover a larger corneal surface, thereby obtaining more detailed corneal topographic information and improving the accuracy of corneal topographic measurement.

[0122] If the comparison results show that the corneal diameter is smaller than the diameter threshold, it indicates that the cornea is relatively small. In this case, the number of rings of the Placido disc is determined to be the second value. For example, for measurements of smaller corneas such as those of chickens or mice, if the diameter threshold is still 10mm, when the measured corneal diameter is less than 10mm, the number of rings of the Placido disc is determined to be 16 rings (here, 16 rings is only a hypothetical example of the second value). It should still be understood that a smaller number of rings is sufficient to meet the measurement needs of smaller corneas, avoiding information redundancy due to too many rings, and simplifying the data processing process.

[0123] The method for determining the Placidho disc ring number based on corneal diameter in this application example is highly practical and adaptable. It can automatically select appropriate measurement parameters for corneal sizes of different dimensions, improving measurement efficiency and accuracy. In ophthalmic clinical practice and research, corneal sizes vary considerably among different species or individuals. This flexible ring number determination method allows corneal topography measurement instruments to be applied to a wider range of subjects, providing reliable data support for accurate diagnosis and treatment.

[0124] In one possible implementation, before analyzing multiple concentric rings contained in the corneal topography imaging based on the shape and number of rings of the Plassid disk to obtain the corneal topography data of the object being tested, the method further includes:

[0125] The magnification of corneal topography imaging is determined based on the corneal diameter.

[0126] By using different lens combinations and depending on the imaging magnification, corneal topography images can be magnified or reduced.

[0127] In this application example, different corneal sizes require different imaging magnifications to ensure that the final acquired corneal topography image not only clearly displays corneal details but also completely covers the entire corneal area. Appropriately adjusting the imaging magnification according to the corneal diameter can optimize image quality and measurement accuracy. For example, a larger magnification is needed for smaller corneas to highlight details, while a smaller magnification is needed for larger corneas to ensure image integrity.

[0128] One specific implementation method is to determine the imaging magnification through a pre-defined mapping relationship. For example, based on clinical experience or experimental data, a piecewise function relationship between corneal diameter and imaging magnification can be established. When the corneal diameter falls within a certain range, a corresponding magnification is set. For instance, when the corneal diameter is less than 5mm, the imaging magnification is set to 3x; when the corneal diameter is between 5mm and 10mm, the imaging magnification is set to 2x; and when the corneal diameter is greater than 10mm, the imaging magnification is set to 1.5x.

[0129] In the Placido disk-based corneal topography system, the corneal surface follows the imaging laws of a spherical mirror, based on the principle of spherical mirror reflection imaging:

[0130]

[0131] Where p is the object distance (mm), q is the image distance (mm), f is the focal length of the spherical lens (mm), r is the radius of corneal curvature (mm), and the magnification of the spherical lens image is:

[0132]

[0133] By magnifying or reducing corneal topography images, it is possible to ensure that images of corneas of different sizes can be accurately acquired and analyzed. Appropriate magnification and lens combinations ensure that images acquired by the CCD camera have suitable size and resolution, avoiding data processing difficulties or information loss due to images that are too large or too small. Simultaneously, it facilitates the accurate calculation of corneal topography data based on information such as the shape and number of concentric rings. A suitable image size ensures accurate extraction of the geometric information of the concentric rings, contributing to the reliability of calculations of data such as corneal curvature radius and corneal surface height.

[0134] In one possible implementation, based on the shape and number of rings of the Plassid disk, multiple concentric rings contained in the corneal topography imaging are analyzed to obtain the corneal topography data of the object being tested, including:

[0135] S401, Obtain the shape and number of multiple concentric rings contained in the corneal topography image;

[0136] S402, based on the shape and number of rings of the Plassid disk, analyzes the shape and number of multiple concentric rings contained in corneal topography imaging, and obtains the numerical value of the spacing variation of multiple concentric rings of the Plassid disk in corneal topography imaging.

[0137] S403, determine the corneal curvature radius of the tested object based on the value of the spacing change.

[0138] In this application example, corneal topography imaging is typically achieved by projecting concentric rings on a Placido disc onto the corneal surface of the object being examined, and then acquiring the image using a specific imaging device (such as a CCD camera). During corneal topography measurement, the acquired corneal topography images are first analyzed.

[0139] To accurately analyze corneal topography data, the shape and number of concentric rings are first obtained from the corneal topography image. The shape of these concentric rings changes due to variations in the curvature of the corneal surface. For example, if the cornea is a perfectly spherical surface, the concentric rings should be nearly perfect circles; however, if there are local irregularities in the cornea, such as in keratoconus, the concentric rings may be distorted or deformed in the affected area, no longer being standard circles. Image processing techniques can be used to extract the edges of these concentric rings, thereby analyzing their shape. Specifically, edge detection can be performed on the image to find the outlines of the concentric rings, and then the geometry of these outlines can be observed, such as whether they are circular, elliptical, or irregular.

[0140] The ring count refers to the number of concentric rings appearing in corneal topography imaging. These concentric rings can be counted after image acquisition. This is done by identifying the outline of each individual concentric ring and counting their number. Since different Plassid discs are pre-designed with different ring counts, and different sizes of corneas require different Plassid discs with different ring counts for measurement, accurately counting the rings in corneal topography imaging is fundamental to subsequent analysis.

[0141] After obtaining the shape and number of concentric rings in corneal topography imaging, the numerical variation in the spacing of these concentric rings in the image was further analyzed. The shape and number of rings of the Plascido disk are known reference information. The known shape (e.g., spherical or conical) and number of rings of the Plascido disk provide a basis for analyzing the variation of concentric rings in corneal topography imaging. For example, for a known spherical Plascido disk, its concentric rings should normally be evenly spaced; while for a conical Plascido disk, the spacing of the concentric rings will be distributed according to certain conical geometric characteristics.

[0142] After projecting the concentric rings of the Plascidus disk onto the corneal surface, the varying curvature of the corneal surface causes changes in the spacing between the concentric rings in the corneal topography image. The change in spacing can be obtained by comparing the distances between adjacent concentric rings in the corneal topography image. This change in spacing reflects the curvature information of the corneal surface. In practice, it is necessary to accurately measure the distances between adjacent concentric rings and compare them at different locations throughout the corneal topography image to obtain the spacing changes in each region.

[0143] The corneal radius of curvature is a key indicator in corneal topography data. The variation in the spacing of the concentric rings obtained in the previous steps can be used to determine the corneal radius of curvature. The corneal radius of curvature is closely related to the variation in the spacing of the concentric rings. From a geometrical optics perspective, the cornea can be approximated as a spherical mirror, and the reflection of the concentric rings of the Plassid disk on the corneal surface follows certain optical laws. When the radius of curvature of the corneal surface varies, the spacing of the concentric rings will change. Based on these spacing variations, combined with known optical and geometric principles, the corneal radius of curvature can be calculated.

[0144] For example, if the spacing between the concentric rings narrows in a certain area, it may mean that the corneal radius of curvature is smaller in that area, i.e., the cornea is steeper in that region; conversely, if the spacing widens in an area, the corneal radius of curvature may be larger, i.e., the cornea is relatively flatter. This is achieved by establishing a suitable corneal topography. Figure 3 D model (such as) Figure 5a As shown in the diagram, by substituting the numerical values ​​of the spacing changes of the concentric rings, the radius of curvature of the cornea at different locations can be calculated. Different Placidos disc shapes and ring numbers will have different calculation methods, but the general principle is to use the physical and geometric relationship between the spacing change and the radius of curvature of the cornea to convert the measured spacing change into a quantitative representation of the radius of curvature of the cornea.

[0145] By employing the above methods and steps—namely, obtaining the shape and number of concentric rings in corneal topography imaging, analyzing the changes in the spacing between the concentric rings, and then determining the corneal curvature radius based on these spacing changes—corneal topography data of the tested object can be obtained. For example... Figure 5b As shown, based on the method of this application, a corneal topography map is obtained by using two-color 3D printing technology. This corneal topography data can then be applied to ophthalmic diagnosis, surgical planning (such as corneal refractive surgery, corneal transplantation surgery, etc.), and contact lens fitting, helping doctors better understand the morphology of the cornea, discover potential corneal lesions (such as keratoconus), and provide accurate basis for the formulation of treatment and correction plans.

[0146] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0147] Corresponding to the corneal topography measurement method in the above embodiment, Figure 6 This is a schematic diagram of the structure of a corneal topography measuring instrument provided in an embodiment of this application, with reference to... Figure 6 The measuring instrument for this corneal topography includes:

[0148] Placido 601;

[0149] The host computer 602 is used to acquire the corneal diameter and corneal vertex of the cornea of ​​the object being tested; determine the distance between the corneal vertex and the vertex of the plascidograph disk; determine the eccentricity of the plascidograph disk; determine the shape of the plascidograph disk based on the eccentricity of the plascidograph disk; and determine the number of rings of the plascidograph disk based on the corneal diameter.

[0150] Optical imaging camera 603 is used to acquire corneal topography images after the concentric rings on the Placido disk are reflected on the corneal surface of the object being tested.

[0151] The host computer 602 is also used to analyze multiple concentric rings contained in corneal topography imaging based on the shape and number of rings of the Plassid disk, and obtain corneal topography data of the object being tested.

[0152] The surface of a Placido disc is covered with multiple concentric rings. Placido discs come in different shapes; they can be spherical, with the concentric rings distributed on the spherical surface, or concentric, with the rings distributed on the sides. Different shapes and numbers of rings allow for the measurement of corneas of varying sizes, ensuring good coverage and accurate measurement. For example, smaller corneas (such as animal corneas) can be accommodated with a disc having fewer rings, while larger corneas (such as human corneas) can be measured with a disc having more rings.

[0153] The host computer has the function of acquiring the corneal diameter and corneal apex of the subject's cornea. The corneal diameter is the maximum span of the cornea in the horizontal or vertical direction, while the corneal apex is an important reference point on the corneal surface. The corneal diameter can be determined using specialized measuring tools or by combining algorithms within the system, based on optical imaging and geometric relationships. Determining the corneal apex helps establish the spatial relationship between the cornea and the Plascidoo disc, providing a basis for subsequent measurements and analysis.

[0154] The host computer can also determine the distance between the corneal apex and the apex of the Placido disc. After measuring or calculating this distance, the host computer can also determine the eccentricity of the Placido disc. Eccentricity is an important determinant of the shape of the Placido disc. Through specific algorithms or pre-set formulas, combined with existing measurement data, the host computer can calculate the eccentricity of the Placido disc.

[0155] Based on the calculated eccentricity of the plascidometry disc, the host computer can determine its shape. Different eccentricities correspond to different shapes (spherical or conical). Simultaneously, the host computer determines the number of rings on the plascidometry disc based on the corneal diameter. Specifically, larger corneal diameters require more concentric rings for precise measurement of the corneal surface, thus a plascidometry disc with a higher number of rings is selected; conversely, for smaller corneas, a plascidometry disc with a lower number of rings is chosen to avoid excessive redundant information and ensure measurement accuracy.

[0156] An optical imaging camera is used to acquire corneal topography images by capturing the reflections of concentric rings on the corneal surface of the subject. During the measurement, the plascidoscopy disk is illuminated (e.g., by a flexible LED unit). The light from the concentric rings reflects off the corneal surface, and the optical imaging camera captures this reflected light and converts it into an image signal. To obtain clear corneal topography images, the camera needs high resolution and good imaging performance, and may be used in conjunction with other optical components, such as a 4F object-side telecentric system and a bandpass filter, to ensure image quality. For example, a 4F object-side telecentric system can reduce imaging errors caused by eye movement, and a bandpass filter can filter out stray light and improve the signal-to-noise ratio of the image.

[0157] Another important function of the host computer is to analyze multiple concentric rings contained in corneal topography imaging based on the shape and number of rings of the Plassid disk. First, the acquired corneal topography image is processed to obtain the shape and number of concentric rings.

[0158] Furthermore, the host computer analyzes the spacing changes of the concentric rings in corneal topography imaging based on the shape and number of rings of the Plassid disk. Since the shape and number of rings of the Plassid disk are known reference information, the host computer can obtain the numerical values ​​of the spacing changes of the concentric rings in corneal topography imaging by comparing and analyzing the reflection imaging of the concentric rings on the cornea.

[0159] It should be understood that the numerical variation in spacing is closely related to the corneal radius of curvature. Using specific geometric optics formulas and algorithms, the host computer can determine the corneal radius of curvature of the object being tested based on these spacing variations, thus obtaining complete corneal topographic data. In one example, the curvature at different locations on the corneal surface can be displayed as a color-coded topographic map, providing ophthalmologists with intuitive information about the corneal surface for clinical applications such as diagnosing eye diseases (e.g., keratoconus), assessing corneal health, and planning corneal refractive surgery or contact lens fitting.

[0160] First, the host computer acquires the corneal diameter and apex information of the subject's cornea. Then, it calculates the distance between the corneal apex and the apex of the Plassid disk, determines the eccentricity of the Plassid disk, and thus determines the shape and number of rings of the disk. Next, an optical imaging camera acquires corneal topography images after reflection from the concentric rings on the Plassid disk onto the corneal surface. Finally, the host computer analyzes the acquired images, processing and calculating the shape, number of rings, and spacing changes of the concentric rings to obtain the final corneal topography data. Through the collaboration of its components and the processing capabilities of the host computer, the corneal topography measurement instrument can accurately measure and analyze the topographic information of the corneal surface, providing crucial data support for ophthalmic clinical practice and research.

[0161] In one possible implementation, the instrument for measuring corneal topography also includes:

[0162] The object-side telecentric system is used to determine the imaging magnification of corneal topography based on the corneal diameter; and to magnify or reduce the corneal topography image based on the imaging magnification using different lens combinations.

[0163] In corneal topography measurement instruments, the object-side telecentric system determines the imaging magnification of the corneal topography image based on the corneal diameter. Corneal diameter is a crucial parameter because different corneal sizes require different magnifications to achieve optimal measurement results. For smaller corneas, a higher magnification is needed to clearly observe and measure corneal details, accurately capturing subtle changes on the corneal surface; conversely, for larger corneas, excessively high magnification may obscure the entire corneal topography, thus requiring a relatively lower magnification. The object-side telecentric system determines the appropriate imaging magnification based on the corneal diameter using a built-in algorithm or preset rules. For example, a mapping function can be used to correlate the measured corneal diameter with different magnifications; for instance, when the corneal diameter falls within a certain range, the appropriate magnification value is selected.

[0164] The object-side telecentric system comprises different lens combinations that can magnify or reduce corneal topography images according to a determined imaging magnification. The lens combinations in this system are typically carefully designed, with different lenses possessing different optical parameters such as focal length. According to the optical imaging formula (where is the object distance, is the image distance, and is the lens focal length), different lens combinations alter the propagation path of light, thereby changing the image size.

[0165] Specifically, for situations requiring magnified imaging, the object-side telecentric system selects a lens combination that magnifies the corneal topography image after light passes through it. For example, selecting a front lens with a short focal length and a rear lens with a long focal length allows light to converge through the front lens and further converge or diverge through the rear lens, ultimately forming a magnified image on the image plane. Conversely, for situations requiring reduced imaging, an opposite lens combination can be selected, such as a front lens with a long focal length and a rear lens with a short focal length, resulting in a smaller image. It should be noted that the switching of these lens combinations can be performed automatically according to preset system rules, or manually selected by the operator based on actual conditions to meet different measurement needs.

[0166] In practice, assuming a small corneal diameter, the system determines, based on predefined rules, that magnification of the corneal topography image is needed. The object-side telecentric system automatically switches the lens combination to magnification mode. Taking a 4F object-side telecentric system as an example, when the front lens and rear lens are selected, the light passing through this lens system is magnified, increasing the ratio of image distance to object distance, thereby magnifying the corneal topography image. Conversely, when the corneal diameter is large and a reduced image is needed, the system can switch to a combination of front and rear lenses to obtain a reduced image.

[0167] The telecentric system allows the corneal topography measuring instrument to adapt to corneas of different sizes by flexibly adjusting the imaging magnification. Since corneas of different species or individuals can vary significantly in size, this system automatically adjusts the image size according to the corneal diameter, avoiding the loss of corneal information due to excessively large images or the inability to accurately measure corneal details due to excessively small images. This improves the accuracy and adaptability of the entire measurement system.

[0168] The object-side telecentric system comprises various lens combinations that can magnify or reduce corneal topography images according to a predetermined magnification. The lens combinations in this system are typically carefully designed, with different lenses possessing different optical parameters such as focal length. This is based on the optical imaging formula... (Where p is the object distance, q is the image distance, f is the focal length of the lens, and r is the radius of curvature of the cornea), different lens combinations will change the propagation path of light, thereby changing the size of the image.

[0169] Specifically, for situations requiring magnified imaging, the object-side telecentric system selects a lens combination that magnifies the corneal topography image after light passes through it. For example, a front lens with a short focal length and a rear lens with a long focal length are selected. The light rays converge through the front lens and further converge or diverge through the rear lens, ultimately forming a magnified image on the image plane. Conversely, for situations requiring reduced imaging, an opposite lens combination can be selected, such as a front lens with a long focal length and a rear lens with a short focal length, resulting in a reduced image.

[0170] In practice, assuming a small corneal diameter, the optical imaging camera determines, according to predefined rules, that magnification of the corneal topography image is required. The object-side telecentric system automatically switches the lens combination to magnification mode. Taking a 4F object-side telecentric system as an example, when a front lens with f1 = 12.5 cm and a rear lens with f2 = 20 cm are selected, the light passing through this lens system will produce a magnification effect, increasing the ratio of the image distance q to the object distance p, thereby achieving magnification of the corneal topography image. Conversely, when the corneal diameter is large and a reduced image is required, the system can switch to a combination of a front lens with f1 = 20 cm and a rear lens with f2 = 12.5 cm to obtain a reduced image.

[0171] After selecting appropriate lens parameters and a Placido disc structure, the subject is instructed to open one eye. Once the light forms a clear image on the subject's retina and focuses successfully, the Placido disc emits light, lifting the subject's upper eyelid to reduce the influence of eyelashes on corneal topography measurements. An optical imaging camera (CCD) captures and records the image. The host computer then analyzes and integrates the acquired imaging data to derive the subject's corneal topography and wavefront aberration of the subject's eye. Measurements are performed on the other eye after one eye is measured. Once both eyes are measured, the results are displayed and recorded on the screen, forming the subject's test file for future reference.

[0172] For example, when measuring the corneas of humans and animals (such as rabbits and mice), the corneal diameters differ significantly. The magnification and reduction functions of the object-side telecentric system ensure that a clear, appropriately sized corneal topography image is obtained regardless of corneal size. The object-side telecentric system not only adjusts the image size but also guarantees image quality and stability. During measurement, due to its telecentric design, the principal ray of the object-side telecentric system is parallel to the optical axis on the object side. This helps reduce problems such as image blurring or image size changes caused by minor changes in corneal position (such as slight eye movements), ensuring measurement accuracy and reliability. Furthermore, the precise design and use of different lens combinations ensure that severe aberrations do not occur during image magnification or reduction, resulting in a corneal topography image with high resolution and contrast. This facilitates the analysis of information such as the shape, number of rings, and spacing changes of concentric rings by the host computer.

[0173] By integrating the telecentric system into the corneal topography measurement instrument, the instrument's functionality is enhanced, enabling more precise and flexible measurement of corneal topography information of different sizes. This provides more accurate and reliable data for ophthalmic clinical practice and research. It also improves the personalized adaptability of corneal measurements, catering to diverse ophthalmic patients.

[0174] One possible implementation is, such as Figure 7 As shown, the object-centric telecentric system (i.e., the 4F object-centric telecentric system) includes:

[0175] Aperture 103, front lens 102 and rear lens 104 of the object-side telecentric lens, wherein:

[0176] Both the front lens 102 and the rear lens 104 are achromatic lenses;

[0177] The aperture of aperture 103 is set to 3-7mm.

[0178] It should be understood that the main function of the aperture 103 is to control the light flux entering the optical imaging camera 603. When the aperture is small, it restricts the light entering the optical imaging camera, thereby reducing aberrations and improving the resolution and contrast of the image. This is because a smaller aperture can block some light rays that are far from the optical axis, making the transmitted light rays closer to the ideal light rays, thus reducing aberrations caused by excessive differences in the angle of light rays. In corneal topography measurement instruments, the aperture of the aperture 130 is set in the range of 3-7mm, which can be adjusted according to the actual situation to achieve the best imaging effect. For example, in cases of strong ambient light or when higher resolution is required, the aperture can be reduced; while when more light is needed to enhance image brightness, the aperture can be appropriately increased. At the same time, the presence of the aperture helps control the depth of field. For corneal topography measurement, a suitable depth of field ensures that concentric rings at different depths on the corneal surface can be clearly imaged. A smaller aperture increases the depth of field, making the image of the entire corneal surface clearer, which helps to accurately analyze the details of the corneal surface.

[0179] In this application example, both the front lens 102 and the rear lens 104 of the object-side telecentric lens are achromatic lenses. An achromatic lens is a specially designed lens that effectively reduces chromatic aberration. During optical imaging, light of different colors (wavelengths) refracts at different angles after passing through a lens due to their different refractive indices, resulting in chromatic aberration. This manifests as colored edges or images of different colors not being in the same position. Achromatic lenses, by combining lenses of different materials or curvatures, allow light of different wavelengths to converge at a closer focal point, thereby reducing chromatic aberration and improving image quality.

[0180] The design and combination of the front and rear lenses of the object-side telecentric lens are crucial for achieving the object-side telecentric characteristic. In corneal topography, the principal ray needs to be parallel to the optical axis on the object side (i.e., the side where the cornea is located) to ensure that the image size remains relatively stable even with slight corneal movement. The focal length, curvature, thickness, and relative position of the front and rear lenses are pre-designed so that after refraction by the lenses, the principal ray remains parallel to the optical axis on the object side.

[0181] Specifically, still as Figure 7As shown, light rays originate from the corneal surface (after reflection by the concentric rings of the Placido disc 601) and first enter the front lens 102 of the object-side telecentric lens. The front lens 102 refracts the light rays for the first time, directing them in a predetermined direction. Then, the light rays undergo further refraction by the rear lens 104, ultimately resulting in a refracted image that can be captured by optical imaging devices such as CCD cameras. Due to the combined effect of the front lens 102 and the rear lens 104, regardless of how the cornea moves within a certain range, as long as the range of movement is within the design range of the object-side telecentric system, the size of the image will not significantly change due to variations in object distance, ensuring the stability and accuracy of the imaging.

[0182] In the corneal topography measurement instrument, the aperture 103, the front lens 102, and the rear lens 104 of the object-side telecentric lens work together. The aperture 103 controls the light flux and image quality, ensuring that the light entering the optical imaging camera 603 is within a suitable range and providing an appropriate depth of field. The front lens 102 and the rear lens 104, as achromatic lenses, not only reduce the impact of chromatic aberration on imaging but also achieve object-side telecentricity through their optical properties, making corneal topography imaging more stable and clear. The object-side telecentric system can adjust the magnification of the image according to the size of the cornea (the corneal diameter is determined by other parts of the object-side telecentric system or the host computer), and magnify or reduce the corneal topography image through different lens combinations, ultimately providing important optical guarantees for obtaining high-quality corneal topography images.

[0183] The aforementioned telecentric system in corneal topography measurement instruments lays a solid optical foundation for obtaining accurate corneal topography data, which helps improve the accuracy, reliability, and adaptability of corneal topography measurement and is of great significance for ophthalmic clinical diagnosis and scientific research.

[0184] One possible implementation is, such as Figure 7 As shown, the instruments for measuring corneal topography also include:

[0185] A bandpass filter 105 is placed in the optical path in front of the optical imaging camera, and the bandpass filtering of the bandpass filter is set to correspond to the wavelength of the illumination source.

[0186] The illumination unit 106 is used to provide an illumination source during corneal imaging.

[0187] During corneal imaging, the illumination unit provides the necessary light source for the entire measurement process, ensuring that the concentric rings on the Placido disk are fully illuminated. This allows the rings to be clearly captured by the optical imaging camera after reflection from the corneal surface. The illumination unit typically uses flexible LEDs or other light sources, and through proper optical path design and illumination control, the light is uniformly distributed across the Placido disk. After reflection from the Placido disk, this light is projected onto the corneal surface, forming a reflected image for measurement. For example, in a Placido disk-based corneal topography instrument, the light emitted by the flexible LED must cover the entire Placido disk, and the light intensity at different locations should be as uniform as possible to ensure consistent reflection intensity of the concentric rings on the corneal surface. This prevents uneven illumination from causing some areas in the image to be too bright or too dark, which would affect the subsequent identification and analysis of the concentric rings.

[0188] A bandpass filter is placed in the optical path in front of an optical imaging camera. The bandpass filtering characteristics of the bandpass filter are set to correspond to the wavelength of the illumination source, that is, only light within a specific wavelength range is allowed to pass through, and this wavelength range is highly matched with the wavelength of the light emitted by the illumination source.

[0189] Because various stray lights are often present in real-world environments, these stray lights can interfere with the optical imaging camera's capture of corneal reflected light, degrading image quality. Bandpass filters effectively filter out ambient light and other stray light of non-target wavelengths, allowing only light corresponding to the wavelength of the illumination source to pass through and enter the optical imaging camera. In this way, the light signal received by the camera mainly comes from the useful light signal reflected by the plascidospheric disk, reducing noise interference and thus improving the image's signal-to-noise ratio. For example, in actual measurement environments, ambient light may contain multiple wavelengths. Without filtering, these stray lights will superimpose with the light reflected by the plascidospheric disk, resulting in blurred images and reduced contrast. Bandpass filters can filter out these stray lights, making the image acquired by the camera clearer and facilitating accurate analysis of information such as the shape and number of concentric rings in corneal topography imaging.

[0190] By allowing only specific wavelengths of light to pass through, bandpass filters result in purer light signals received by optical imaging cameras, more accurately reflecting the true reflection of light from the plascidus disk on the corneal surface. This is crucial for corneal topography data analysis based on optical signals, improving the accuracy and reliability of measurement results. For example, when calculating the corneal radius of curvature using the variation in the spacing between concentric rings in corneal topography imaging, pure light signals ensure clearer edges of the concentric rings and more accurate spacing measurements, thereby improving the precision of corneal radius of curvature calculations.

[0191] In this application example, dual-color 3D technology can be used to process the Placido disk, effectively combining two colored materials to form multiple independent concentric rings that meet design requirements. Dual-color 3D technology improves the forming accuracy and bonding strength of the Placido disk, ensuring the stability of the optical design and measurement accuracy. Furthermore, the 4F object-side telecentric system further optimizes the imaging quality of the Placido disk. By selecting different combinations of achromatic lenses and aperture settings, adaptation to different corneal sizes and improved image clarity can be achieved. Combined with a bandpass filter, clear and accurate corneal reflection image data can be effectively acquired under green or red LED illumination.

[0192] Through the above improvements, the application of this application example in corneal topography measurement significantly improves the overall accuracy, repeatability and data reliability, enabling the corneal topography measuring instrument to more accurately capture the minute morphological features of the corneal surface, making it particularly suitable for various needs in the diagnosis and treatment of corneal diseases.

[0193] Compared with the design of traditional corneal topography instruments, the example in this application has made significant improvements in the following aspects:

[0194] Manufacturing cost: The use of dual-color 3D printing technology enables precise processing of the Placido disk, which simplifies the production process, reduces complicated assembly steps, and improves the bonding accuracy, making the manufacturing process of the Placido disk simpler and thus reducing the overall production cost.

[0195] Accuracy and Adaptability: The Placido disc is designed to adaptively adjust to different corneal sizes and curvatures, ranging from small animals (such as mice, with a fewer concentric circle design) to large species (such as humans, with a more concentric circle design), to improve the resolution of corneal topography in various applications. This personalized adjustment makes measurements more accurate and effectively overcomes the limitations of existing technologies when dealing with different corneal structures.

[0196] Imaging quality and stability: The use of the 4F object-side telecentric system improves the magnification and reduction functions of the image. Combined with the green / red LED illumination unit and bandpass filter, it can achieve high-quality imaging under different lighting conditions, ensuring the clarity and consistency of corneal reflection images and solving the problem of imaging stability in existing equipment.

[0197] Enhanced reliability and durability: The combination of dual-color 3D processing and achromatic lenses makes the Placido disc more durable. The dual-color processing also ensures the bonding strength of the materials, thereby improving the reliability of the system in long-term use and reducing the need for replacement and maintenance due to material fatigue.

[0198] Component simplification and overall design optimization: The 4F telecentric system, through a reasonable combination of lenses, can adapt to different corneal sizes, reducing dependence on specific components, thereby simplifying the equipment structure, reducing the number of components that need maintenance, and making the system simpler and easier to operate.

[0199] In summary, the multiple optimized designs and innovative technologies of this application have jointly improved the performance of the corneal topography measurement instrument in clinical applications, providing not only higher measurement accuracy for corneal topography measurement, but also greater production efficiency and durability.

[0200] This application also provides an electronic device, which includes one or more processors and a memory;

[0201] The memory is coupled to one or more processors. The memory is used to store computer program code, which includes computer instructions. The one or more processors call the computer instructions to cause the electronic device to perform the corneal topography measurement method described above.

[0202] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. The electronic device 800 can be a mobile phone, smart screen, tablet computer, wearable electronic device, in-vehicle electronic device, augmented reality (AR) device, virtual reality (VR) device, laptop computer, ultra-mobile personal computer (UMPC), netbook, personal digital assistant (PDA), projector, or a communication device such as a server, storage device, or base station, or a smart car, etc. This application embodiment does not impose any limitations on the specific type of electronic device.

[0203] The memory 801 can be used to store computer software programs 802 and modules. The processor 803 executes various functional applications and data processing of the electronic device by running the software programs and modules stored in the memory 801. The memory 801 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the electronic device (such as audio data, telephone book, etc.). In addition, the memory 801 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0204] The processor 803 may include one or more processors such as a central processing unit (CPU), an application processor (AP), and a baseband processor. The processor can serve as the nerve center and command center of the wireless router. The processor 803 can generate operation control signals based on instruction opcodes and timing signals to control instruction fetching and execution. The memory 801 can be used to store executable program code, including instructions. The processor 803 executes various functional applications and data processing of the network device by running the instructions stored in the memory. The memory 801 may include a program storage area and a data storage area, such as storing data for audio signals to be played. For example, the memory may be Double Data Rate Synchronous Dynamic Random Access Memory (DDR) or Flash memory.

[0205] This application also provides a computer-readable storage medium storing computer instructions; when the computer-readable storage medium is used on an electronic device, it causes the electronic device to perform the aforementioned method for measuring corneal topography.

[0206] Computer instructions can be stored in or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. A computer-readable storage medium can be any available medium that a computer can access, or it can contain one or more data storage devices such as servers or data centers that can be integrated with that medium. Available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media, or semiconductor media (e.g., solid-state disks (SSDs)).

[0207] This application also provides a computer program product containing computer instructions, which, when run on an electronic device, enables the electronic device to perform the aforementioned method for measuring corneal topography.

[0208] The computer storage medium and computer program product provided in the above embodiments of this application are used to execute the methods provided above. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects corresponding to the methods provided above, and will not be repeated here.

[0209] In the above embodiments, implementation can also be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line, DSL) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer, or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., Digital Versatile Discs (DVDs)), or semiconductor media (e.g., Solid State Disks (SSDs)).

[0210] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0211] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments claimed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0212] In the embodiments provided in this application, it should be understood that the disclosed apparatus / network devices and methods can be implemented in other ways. For example, the apparatus / network device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0213] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0214] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for measuring corneal topography, characterized in that, include: Obtain the corneal diameter and corneal vertex of the object being tested; Determine the distance between the corneal apex and the apex of the Placido disc, and determine the eccentricity of the Placido disc; The shape of the placido disc is determined based on the eccentricity of the placido disc, and the number of rings of the placido disc is determined based on the corneal diameter; The concentric rings on the Placido disk are used to acquire corneal topography images after reflection from the corneal surface of the object being tested; Based on the shape and number of rings of the Placido disk, the corneal topography data of the tested object is obtained by analyzing the multiple concentric rings contained in the corneal topography imaging.

2. The method according to claim 1, characterized in that, Determining the distance between the corneal apex and the apex of the Placido disk, and determining the eccentricity of the Placido disk, includes: Determine the distance between the corneal vertex and the vertex of the plascido disk to be designed, as well as the object distance between the plascido disk and the optical imaging camera; Based on the distance and object distance, the sagitta of each ring of the Placido disk is determined, wherein the Placido disk comprises multiple independent concentric rings; The eccentricity of the Plassid disk is determined based on the sagitta of each ring of the Plassid disk, the radius of curvature of the vertex of the Plassid disk, and the radius of each ring of the Plassid disk.

3. The method according to claim 1, characterized in that, Determining the shape of the Placido disk based on its eccentricity includes: If the eccentricity of the Plassido disk is zero, then the shape of the Plassido disk is determined to be spherical, wherein when the Plassido disk is spherical, concentric rings in the Plassido disk are distributed on the surface of the Plassido disk; If the eccentricity of the Plassid disk is greater than zero and less than a predetermined value, then the shape of the Plassid disk is determined to be conical, wherein when the Plassid disk is conical, the concentric rings in the Plassid disk are distributed on the side of the Plassid disk.

4. The method according to claim 1, characterized in that, Determining the number of rings of the Placido disc based on the corneal diameter includes: Compare the corneal diameter with a predetermined diameter threshold; If the comparison result indicates that the corneal diameter is greater than or equal to the diameter threshold, then the number of rings of the Placidor disc is determined to be the first value; If the comparison result indicates that the corneal diameter is less than the diameter threshold, then the number of rings of the Placidor disc is determined to be a second value, wherein the first value is greater than the second value.

5. The method according to claim 1, characterized in that, Before analyzing the multiple concentric rings contained in the corneal topography image based on the shape and number of rings of the Plassid disk to obtain the corneal topography data of the object being tested, the method further includes: The imaging magnification of the corneal topography image is determined based on the corneal diameter. By using different lens combinations and depending on the imaging magnification, corneal topographic imaging can be magnified or reduced.

6. The method according to claim 1, characterized in that, The method involves analyzing multiple concentric rings contained in the corneal topography image based on the shape and number of rings of the Plascidus disc to obtain the corneal topography data of the detected object, including: Obtain the shape and number of concentric rings contained in the corneal topography image; Based on the shape and number of rings of the Placido disk, the shape and number of rings of multiple concentric rings contained in the corneal topography imaging are analyzed to obtain the numerical value of the spacing variation of the multiple concentric rings of the Placido disk in the corneal topography imaging. The corneal curvature radius of the tested object is determined based on the value of the spacing change.

7. An instrument for measuring corneal topography, characterized in that, include: Placido disc; The host computer is used to obtain the corneal diameter and corneal apex of the object being tested; Determine the distance between the corneal apex and the apex of the plascidometry disc; determine the eccentricity of the plascidometry disc; determine the shape of the plascidometry disc based on its eccentricity; and determine the number of rings of the plascidometry disc based on the corneal diameter. An optical imaging camera is used to acquire corneal topography images after the concentric rings on the Placido disk are reflected on the corneal surface of the object being tested; The host computer is also used to analyze multiple concentric rings contained in the corneal topography imaging based on the shape and number of rings of the Plassid disk, and obtain the corneal topography data of the object being detected.

8. The measuring instrument according to claim 7, characterized in that, The instrument for measuring corneal topography also includes: The object-side telecentric system is used to determine the imaging magnification of the corneal topography image based on the corneal diameter; and to perform magnification or reduction processing on the corneal topography image based on the imaging magnification using different lens combinations.

9. The measuring instrument according to claim 8, characterized in that, The object-centric telecentric system includes: The aperture stop, the front lens and the rear lens of the object-side telecentric lens, wherein: Both the front lens and the rear lens are achromatic lenses; The aperture of the aperture is set to 3-7mm.

10. The measuring instrument according to any one of claims 7 to 9, characterized in that, The instrument for measuring corneal topography also includes: An illumination unit is used to provide an illumination source during corneal imaging; A bandpass filter is placed in the optical path in front of the optical imaging camera, and the bandpass filtering of the bandpass filter is set to correspond to the wavelength of the illumination source.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it causes the electronic device to implement the method as described in any one of claims 1 to 6.

12. A computer program product, characterized in that, Includes a computer program, which, when run, causes the method as described in any one of claims 1 to 6 to be performed.

13. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 6.

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