Cornea effective optical zone measuring method based on Sirus anterior segment three-dimensional imaging analysis instrument

Abstract

The invention provides a cornea effective optical zone measurement method based on a Sirius anterior segment three-dimensional imaging analysis instrument, and solves the problems of time consumption and low accuracy in cornea effective optical zone measurement at present. Comprising the following steps: 1) extracting data: respectively acquiring corneal topographic maps before and after an operation by utilizing a Sirus anterior segment three-dimensional imaging analysis instrument; exporting original data in the two corneal topography maps, and extracting data required by calculation; 2) calculating the effective optical area of the cornea: carrying out difference calculation on the two corneal topography maps, and subtracting the primary data of the preoperative corneal topography map from the extracted primary data of the postoperative corneal topography map to obtain difference data of the corneal topography maps; finding out a front point and a rear point which are located in the same direction, start from an original point and have difference data from a negative value to a positive value for the first time through the difference data, establishing a linear function in the direction through the two points, and calculating an effective optical region boundary point; and calculating the size of the actual effective optical region according to all the obtained effective optical region boundary points.

Description

Technical Field

[0001] The invention belongs to the technical field of corneal effective optical zone measurement, and in particular relates to a corneal effective optical zone measurement method based on a Sirius anterior segment three-dimensional imaging analysis instrument. Background Art

[0002] The effective optical zone (EOZ) is considered to be the area of ​​the cornea that achieves the expected correction after corneal refractive surgery. This area should provide the cornea with good visual quality and minimal wavefront aberration. According to existing studies, the EOZ after corneal refractive surgery is usually smaller than the optical zone designed before surgery. The reason may be caused by the postoperative wound healing process, biomechanical response and corneal epithelial remodeling. Therefore, EOZ not only indicates the visual quality after surgery, but also indicates the safety and effectiveness of the surgery, becoming an important indicator for evaluating corneal refractive surgery. Similarly, in myopia prevention and control, in orthokeratology, one of the most effective means, the effective optical zone is regarded as an important indicator for evaluating the fitting of orthokeratology lenses. Current studies show that the size and position of the effective optical zone are important indicators affecting myopia prevention and control.

[0003] The commonly used method for measuring the effective optical zone of the cornea is as follows: first, taking the Sirius anterior segment three-dimensional imaging analysis instrument as an example, in the "Compare" interface of the topographic mapping software Phoenix, select the corneal topography before and after surgery (keratorefractive surgery or orthokeratology surgery); then, in the tangential curvature difference map (such as Figure 1 Move the cursor along the meridian from the center to both ends, and stop when the cursor displays "0.00D" (i.e. Figure 1 The green boundary where the blue turns to red from the center outward) and record the coordinates of both ends as (x, y) and (x', y'). Measure once every 30° on the meridians from 0° to 180°, and take 6 values ​​in total. Sum the two radii on the same meridian and use the formula Calculate the diameter of the optical zone of each meridian. The EOZ diameter is the average of the diameters of the optical zones of the six meridians (0°-180°, 30°-210°, 60°-240°, 90°-270°, 120°-300°, and 150°-330°). If you need to calculate the area of ​​the effective optical zone, use S=πr 2 However, this method obviously has the following problems when measuring the effective optical zone of the cornea:

[0004] 1. Manual measurement takes a lot of time and energy. It takes a long time to measure each point, about 15 seconds. Then, it takes 2-3 minutes to measure one eye plus calculation time. If you want to use other types of topographic maps, you need to repeat the above operations, which is time-consuming;

[0005] 2. Calculate 6 radii by finding 12 points, and then further calculate the area. When the effective optical area is irregular, it will be different from the actual size, and the measurement accuracy is low;

[0006] 3. The common corneal morphology examination equipment currently on the market can produce two morphological difference maps, but it does not perform calculations and analysis on other data such as the optical zone, and still requires manual measurement.

[0007] Although other scholars have performed computer extraction on the images collected by the Pentacam device (three-dimensional anterior segment analysis and diagnosis system), specifically identifying and extracting the colors of the output images, which saves time and manpower compared to manual measurement, different hospitals have different color scale settings for the images, resulting in different extraction results in the same situation, which is not widely applicable.

[0008] In view of the above problems, the present invention believes that it is necessary to explore a faster and more accurate method for measuring the effective optical zone of the cornea. Summary of the invention

[0009] The purpose of the present invention is to solve the shortcomings of the current measurement of corneal effective optical zone, which is time-consuming and has low accuracy, and to provide a corneal effective optical zone measurement method based on the Sirius anterior segment three-dimensional imaging analysis instrument.

[0010] The concept of the present invention:

[0011] In view of the technical problems existing in the current background technology, the researchers of the present invention have conducted a comprehensive analysis and believe that in order to solve the problem of time-consuming and low measurement accuracy, first of all, the intervention of manual measurement methods should be reduced or even avoided, and the fast and accurate advantages of computer processing should be used to improve the measurement speed. Secondly, the accuracy should be improved by improving the true restoration of the shape of the effective optical zone (collecting more points).

[0012] Sirius anterior segment 3D imaging analysis instrument is a comprehensive instrument for ophthalmic examination, mainly used for corneal topography and anterior segment analysis. It can provide high-precision corneal topography, corneal thickness measurement, anterior chamber depth and other parameters. It is widely used in pre-refractive surgery evaluation, corneal disease diagnosis, anterior segment comprehensive analysis, auxiliary diagnosis and treatment. The working principle of this device mainly relies on the following two technologies:

[0013] 1. Scheimpflug imaging technology: This is a rotational imaging technology that captures multi-angle slice images of the anterior segment of the eye by rotating the camera and laser light source. These images are then processed by a computer to generate a detailed three-dimensional model for measuring parameters such as corneal thickness and anterior chamber depth.

[0014] 2. Placido disc technology: This technology places a disc with concentric rings in front of the eye and measures the morphology of the corneal surface through the reflected light of the rings. The deformation of the reflected light can be used to calculate the curvature of the cornea and generate a corneal topography map.

[0015] These two technologies are currently the two most commonly used technologies for measuring corneal morphology, but most corneal topography acquisition devices only use one of the principles. The Sirius device combines the two measurement technologies to detect corneal morphology, and can perform in-depth analysis from multiple angles, collecting more types of data with higher accuracy.

[0016] The current existing methods for measuring the effective optical zone are mainly used for corneal refractive surgery or orthokeratology, and often only one type of data is used for analysis. With the continuous development of corneal refractive surgery and the urgent need for myopia prevention and control in recent years, the public's requirements for the safety and postoperative effects of corneal refractive surgery are also constantly increasing, and the requirements for orthokeratology are also constantly increasing. However, with the current equipment, there is no direct, fast and effective method.

[0017] Then, combining the concept of solving the problem of the aforementioned invention and the advantages of the Sirius anterior segment three-dimensional imaging analysis instrument itself, the present invention intends to explore a method for measuring the effective optical zone of the cornea based on the Sirius anterior segment three-dimensional imaging analysis instrument, fully utilizing the advantages of the equipment itself to solve the current increasing demand.

[0018] Based on the above invention objectives, in order to achieve the invention objectives, the technical solution provided by the present invention is:

[0019] A method for measuring the effective optical zone of the cornea based on the Sirius anterior segment three-dimensional imaging analysis instrument is special in that it includes the following steps:

[0020] 1) Extract data

[0021] 1.1) Using Sirius anterior segment three-dimensional imaging analysis instrument to collect corneal topography before and after surgery, the preoperative corneal topography and postoperative corneal topography were obtained;

[0022] 1.2) Export the raw data from the two corneal topography images and extract the data required for calculation;

[0023] 2) Calculate the corneal effective optical zone

[0024] 2.1) Calculate the difference between the two corneal topography images and use the extracted postoperative corneal topography Figure 1 The preoperative corneal topography was subtracted from the data Figure 1 Secondary data, to obtain the difference data of corneal topography;

[0025] 2.2) After refractive surgery or orthokeratology, the central area is negative, and the point with a difference of zero is the boundary of the effective optical zone; considering the step size of the acquisition points in each direction (i.e., each line) of the existing Sirius anterior segment three-dimensional imaging analysis instrument, it is difficult to find the acquisition point exactly at 0. Therefore, the difference data is used to find the two points (x1, y1) and (x2, y2) before and after the origin in the same direction where the difference data first changes from negative to positive, and a linear function in this direction is established through the two points:

[0026]

[0027] Where x is the distance from the origin and y is the value of the point;

[0028] Substitute the above formula to calculate (x0,0) as the effective optical zone boundary point in this direction, that is, the calculated 0 point is the effective optical zone boundary point;

[0029] Calculate all directions of corneal topography collection one by one to obtain the effective optical zone boundary points in all directions;

[0030] 2.3) Based on all the effective optical zone boundary points obtained in step 2.2), the size of the actual effective optical zone (the size is information such as radius and area) is calculated.

[0031] Furthermore, in step 1.2), the corneal topography contains original data of 7936 points, and the distribution pattern of the 7936 points is:

[0032] Starting from the origin, data from 0 to 6 mm is collected on each line with a step of 0.2 mm. A total of 256 lines are collected with a step of 1.40625°.

[0033] The raw data of each point includes ten types of data collected from the cornea, namely, the tangential, axial, height (i.e., absolute height) and refractive power data of the anterior and posterior surfaces of the cornea, as well as the corneal thickness and total corneal refractive power data;

[0034] The above is the factory setting data of the Sirius anterior segment three-dimensional imaging analysis instrument used in the present invention, that is, the corneal topography collected by the Sirius anterior segment three-dimensional imaging analysis instrument used in the present invention, including the above information;

[0035] Meanwhile, in step 1.2), data extraction refers to extracting the required data, mainly extracting the specific data of the cornea. According to the data collected by Sirius, there are 10 options: corneal thickness data (CornealThickness), anterior surface height map data (ElevationAnterior), posterior surface height map data (ElevationPosterior), full corneal refractive power map data (RefractiveEquivalentPower), anterior surface refractive power map data (RefractiveFrontalPowerAnterior), posterior surface refractive power map data (RefractiveFrontalPowerPosterior), anterior surface axial map data (SagittalAnterior), posterior surface axial map data (SagittalPosterior), anterior surface tangential map data (TangentialAnterior) and posterior surface tangential map data (TangentialPosterior). The extracted data is formed into a new xlsx file and stored in the specified path.

[0036] Furthermore, in step 2.2), 256 effective optical zone boundary points are obtained.

[0037] Furthermore, in step 2.3), the fitting circle is calculated for the 256 effective optical zone boundary points by the least square method to obtain the fitting circle data, and the fitting circle drawing is performed accordingly (the software for fitting the circle can use the existing software, using the corresponding drawing elements and storing them in the path of the target file).

[0038] Furthermore, in order to help the operator check whether there are any abnormalities in the analysis, the accuracy test was continued, including:

[0039] 2.4) Calculate the size of the fitting circle obtained in step 2.3) and compare it with the size of the actual effective optical zone calculated in step 2.3), and output the analysis image at the same time.

[0040] Advantages of the present invention:

[0041] 1. The measurement method of the present invention saves a lot of time and manual effort because it uses computer extraction and calculation. It only takes 5 seconds to extract data, calculate the effective optical zone and output the results for one eye, which is about one-third of the time it takes to find the coordinate position of a point in the previous method. At the same time, the present invention can perform batch operations at one time, which greatly improves efficiency compared to the current method that can only analyze the effective optical zone once.

[0042] 2. Compared with the existing method that only collects 4 to 6 points and has certain errors in calculation, the present invention collects a large number of points (such as 256 points) for calculation in a short time, and when the effective optical zone is irregular, the actual size can be obtained, providing more precise indicators and prompts in clinical work.

[0043] 3. The present invention can calculate ten different data collected in the corneal topography of the Sirius anterior segment 3D imaging analysis instrument, not limited to the data of the corneal tangent map. When there is an abnormality in the calculation of one data, other data can be used for evidence. At the same time, the data selection is richer, and personalized and specialized selection can be made according to the different surgical methods and different refractive means, giving full play to the functions and technical advantages of the Siriu anterior segment 3D imaging analysis instrument.

[0044] 4. Currently, some effective optical zone calculations are mostly used after refractive surgery, but the present invention is based on a differentiation algorithm to find the morphological boundary of the effective optical zone, which is not limited to the calculation of the optical zone after refractive surgery, but can also be applied to the measurement of the effective optical zone and eccentricity after orthokeratology, providing evaluation indicators related to orthokeratology and myopia prevention and control.

[0045] 5. The present invention subsequently adds the calculation of the fitting circle and the comparison of the size of the actual effective optical zone, and outputs the analysis picture at the same time, which helps the operator to check whether there are any abnormalities in the analysis and conducts an accuracy test. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the tangential curvature difference map;

[0047] Figure 2 To fit the circle picture;

[0048] Figure 3 A comparison diagram of the effective optical zone diameter measured by the method of the present invention and the traditional method;

[0049] Figure 4 This is the relationship between the correction degree of all-femtosecond surgery and the diameter of the effective optical zone; DETAILED DESCRIPTION

[0050] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0051] A method for measuring the effective optical zone of the cornea based on the Sirius anterior segment three-dimensional imaging analysis instrument, using development software based on the logic of the present invention, comprises the following steps:

[0052] 1) Extract data

[0053] 1.1) Using Sirius anterior segment three-dimensional imaging analysis instrument to collect corneal topography before and after surgery, the preoperative corneal topography and postoperative corneal topography were obtained;

[0054] 1.2) Export the raw data of all points in the two corneal topography maps;

[0055] The corneal topography contains raw data of 7936 points, and the distribution pattern of the 7936 points is:

[0056] Starting from the origin, data of 0-6mm is collected on each line with a step of 0.2mm; a total of 256 lines are collected with a step of 1.40625°.

[0057] Among them, the original data of each point includes ten types of data collected from the cornea, namely corneal thickness data (CornealThickness), anterior surface height map data (ElevationAnterior), posterior surface height map data (ElevationPosterior), full corneal refractive power map data (RefractiveEquivalentPower), anterior surface refractive power map data (RefractiveFrontalPowerAnterior), posterior surface refractive power map data (RefractiveFrontalPowerPosterior), anterior surface axial map data (SagittalAnterior), posterior surface axial map data (SagittalPosterior), anterior surface tangential map data (TangentialAnterior) and posterior surface tangential map data (TangentialPosterior).

[0058] In this embodiment, the desired data is exported according to the operation in the user manual of the Sirius anterior segment three-dimensional imaging analysis instrument. The first (preoperative) data needs to be named "00.xlsx", and the second (postoperative) data needs to be named "01.xlsx", and they are placed in a folder named "P_1". If you want to analyze multiple cases, repeat the above steps, and the numbers of the folder names can be increased in sequence. For example, if you want to analyze the effective optical zone of 10 people this time, you need to create 10 folders from "P_1" to "P_10", and name the data of both sides of each person before and after the operation according to the above naming method and place them in the corresponding folders.

[0059] 1.3) Extract corresponding data according to usage needs;

[0060] Data extraction is to extract the required data, and the required data is extracted from the above-mentioned exported data through the development software based on the logic of the present invention. The extracted data will form a new xlsx file and be stored in a specified path.

[0061] 2) Calculate the effective optical area

[0062] 2.1) Calculate the difference between the two corneal topography images and use the extracted postoperative corneal topography Figure 1 The preoperative corneal topography was subtracted from the data Figure 1 Secondary data, to obtain the difference data of corneal topography;

[0063] 2.2) After refractive surgery or orthokeratology, the central area is negative, and the point with a difference of zero is the boundary of the effective optical zone; considering that the Sirius anterior segment 3D imaging analysis instrument collects points in each direction (i.e., each line) with a step of 0.2mm, it is difficult to find the point exactly at 0. Therefore, the difference data is used to find the two points (x1, y1) and (x2, y2) before and after the difference data on each line from the origin for the first time from negative to positive, and a linear function is established through the two points:

[0064]

[0065] Where x is the distance from the origin, y is the value of the point, and (x0,0) is calculated to be the boundary point of the effective optical zone in this direction;

[0066] Calculate each line one by one to obtain 256 effective optical zone boundary points;

[0067] 2.3) According to the 256 effective optical zone boundary points obtained in step 2.2), the size of the actual effective optical zone (the size is information such as radius and area) is calculated; at the same time, the 256 effective optical zone boundary points are used to calculate the fitting circle by the least square method to obtain the fitting circle data, and the fitting circle is drawn based on the corresponding software, such as Figure 2 As shown, the blue point is the actual effective optical area, and the red point is the fitting circle, which is stored in the path of the target file.

[0068] Step 2.4) calculates the size of the fitting circle obtained in step 2.3) and compares it with the size of the actual effective optical zone calculated in step 2.2), and outputs an analysis image at the same time.

[0069] In the entire step 2), by using the above-mentioned development software based on the logic of the present invention to perform differential analysis, the extracted data can be calculated, analyzed, stored, and an analysis chart can be output.

[0070] In order to verify the measurement effect of the method of the present invention, the present invention also carried out optical zone analysis during refractive surgery (50 times), z-night optical zone analysis (150 times), Punov pupil, α effective optical zone (158 times), and effective optical zone of a single patient during the entire reshaping process (10 times).

[0071] For example: The method provided by the present invention was verified in practice in a study used to explore the effect of pre-surgery refractive error on the postoperative effective optical zone (EOZ) after SMILE (all-femtosecond laser micro-incision corneal lenticule extraction). 27 patients (27 eyes) with myopic astigmatism whose astigmatism degree was ≤1.50D and whose programming optical zone (POZ) diameter was 6.5mm were included.

[0072] like Figure 3 and Figure 4 As shown in the figure, the software developed based on the method of the present invention was used to process the corneal tangential curvature map before surgery and the corneal tangential curvature map 1 month after surgery to calculate the size of the effective optical zone, analyze the size difference between the effective optical zone after surgery and the designed optical zone, and analyze the correlation between the effective optical zone after surgery and the degree of refractive error before surgery. The results showed that the area of ​​EOZ was 24.4901±2.2540mm 2 (diameter is 5.5785±0.2551mm), which is significantly smaller than the POZ area of ​​33.1831mm 2 (diameter is 6.5㎜) (P<0.001), which is statistically significant. The postoperative effective optical zone and the preoperative refractive error degree are positively correlated (y=6.2122+0.1309x, R2=0.6304). It is concluded that the postoperative effective optical zone EOZ of SMILE is smaller than the designed optical zone POZ, and the postoperative effective optical zone and the preoperative refractive error degree are positively correlated. At the same time, the present invention also adopts the traditional 8-point method for measurement, and the Bland-Altman consistency analysis (P>0.01) shows no statistical difference and good consistency. Using the traditional method, it takes about 130 minutes to obtain only the size of the effective optical zone. Using this patent, it takes a total of 3 minutes to obtain all the data, including: the size and position of the effective optical zone, the size and position of the fitting circle, the central point value, etc. It can be seen that the present invention has made significant progress.

[0073] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for measuring the effective optical zone of the cornea based on the Sirius anterior segment three-dimensional imaging analysis instrument, characterized in that: The following steps are involved: 1) Extract data 1.1) Using Sirius anterior segment three-dimensional imaging analysis instrument to collect corneal topography before and after surgery, the preoperative corneal topography and postoperative corneal topography were obtained; 1.2) Export the raw data from the two corneal topography images and extract the data required for calculation; 2) Calculate the corneal effective optical zone 2.1) Calculate the difference between the two corneal topography images, and subtract the extracted data of the first corneal topography image before and after surgery from the data of the first corneal topography image after surgery to obtain the difference data of the corneal topography image; 2.2) Use the difference data to find the two points (x1, y1) and (x2, y2) in the same direction where the difference data changes from negative to positive for the first time, and use the two points to establish a linear function in that direction: Where x is the distance from the origin and y is the value of the point; Substitute the above formula to calculate (x0,0) as the effective optical zone boundary point in this direction; Calculate all directions of corneal topography collection one by one to obtain the effective optical zone boundary points in all directions; 2.3) Based on all effective optical zone boundary points obtained in step 2.2), the size of the actual effective optical zone is calculated.

2. The method for measuring the effective optical zone of the cornea based on the Sirius anterior segment three-dimensional imaging analysis instrument according to claim 1, characterized in that: In step 1.2), the corneal topography contains raw data of 7936 points, and the distribution pattern of the 7936 points is: Starting from the origin, data from 0 to 6 mm is collected on each line with a step of 0.2 mm. A total of 256 lines are collected with a step of 1.40625°. Among them, the raw data of each point includes ten types of data collected from the cornea, namely the tangential, axial, height and refractive power data of the anterior and posterior surfaces of the cornea, as well as the corneal thickness and total corneal refractive power data.

3. The method for measuring the effective optical zone of the cornea based on the Sirius device according to claim 2, characterized in that: In step 2.2), 256 effective optical zone boundary points are obtained.

4. The method for measuring the effective optical zone of the cornea based on the Sirius device according to claim 3, characterized in that: In step 2.3), the fitting circle is calculated by the least square method for the 256 effective optical zone boundary points to obtain the fitting circle data, and the fitting circle drawing is performed based on the data.

5. The method for measuring the effective optical zone of the cornea based on the Sirius device according to claim 3, characterized in that: Also includes: 2.4) Calculate the size of the fitting circle obtained in step 2.3) and compare it with the size of the actual effective optical zone calculated in step 2.3), and output the analysis image at the same time.

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