WO2021004030A2 - Color vision function examination method based on visual evoked potential - Google Patents

Description

Color vision function inspection method based on visual evoked potential Technical field

The invention relates to the technical field of brain-computer interface and color vision function inspection, in particular to a color vision function inspection method based on visual evoked potentials.

Background technique

Human color vision is mainly determined by the three types of cone cells on the retina. The absorption peaks of the three types of cone cells are long wavelength (L), medium wavelength (M), and short wavelength (S). Abnormal cone cells can cause color vision defects. The incidence of color vision defects is 8% in men and 0.5% in women. Under normal circumstances, abnormal color vision is divided into three types: abnormal trichromatic vision (color weakness), dichromatic vision (color blindness) and total color blindness. Among them, color weakness can be subdivided into weak red, weak green and weak blue. Color blindness can be subdivided into protanopia, deuteranopia and blue blindness.

Traditional color vision detection mainly includes color blindness detection book (false color map), FM100 color chess detection and other psychophysical methods. These methods mostly rely on subjective judgment and cannot quantify color vision defects. It is not suitable for children's color vision testing and clinical quantitative color vision testing.

Brain-computer interface (BCI) and electroencephalogram (EEG), especially scalp EEG, such as scanning visual evoked potential (sVEP), steady-state visual evoked potential (SSVEP), and pattern visual evoked potential (PVEP) for color vision function tests Provides a more objective and more direct new method to evaluate visual function. There is no related literature on visual evoked potentials in color vision examination.

Summary of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a color vision function inspection method based on visual evoked potential, by designing a series of steady-state visual evoked potential (SSVEP) paradigms with different red and green brightness contrast values, and propose corresponding The qualitative and quantitative criteria for color vision provide an objective and quantitative measurement method for the color vision function in eye examinations.

In order to achieve the above objectives, the technical solutions adopted by the present invention are:

The color vision function inspection method based on visual evoked potential includes the following steps:

1) Red and green flip stimulus paradigm: using the mode flip SSVEP method in the brain-computer interface, the periodic flip presentation of the paradigm pattern texture is drawn through MATLAB using Psychophysics Toolbox programming, which can stabilize the stimulus and induce SSVEP; the sports stimulus target appears as alternate red The green squares, red squares and green squares are equal in size, same in number, and arranged alternately; during the stimulus presentation process, the overall brightness and overall size of the paradigm remain unchanged; the flip frequency of the paradigm is defined as the stimulus frequency, and the pattern of the paradigm is in a cycle Changed twice within;

2) Stimulus paradigm red-green brightness ratio gradient: to ensure that the red-green chromaticity information and total brightness remain unchanged, change the red-green brightness ratio of the stimulus paradigm so that the ratio of red to total brightness in red and green is 0,0.1,0.2, 0.3, 0.4, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.7, 0.8, 0.9 and 1.0 total 27 gradient;

3) Construction of brain-computer interface platform: Before the experiment, the reference electrode was placed on the subject’s left earlobe, the ground electrode was placed on the subject’s forehead, and the measurement electrode was placed on the occipital area of the head; the electrode was connected to the EEG acquisition module, and enlarged , After filtering, digital-to-analog conversion, output EEG signals to the computer for further data processing;

4) Presentation of the stimulus paradigm: The computer expands the display to present the stimulus paradigm on the high refresh rate display; during the experiment, the user needs to follow the screen prompts to watch the stimulus paradigm; during the experiment, the subject needs to sit in the laboratory every time Perform binocular test once; collect the EEG signal generated when the user is looking at the paradigm through EEG acquisition equipment, after amplifying, filtering and A/D conversion, input the processed EEG signal into the computer and use canonical correlation analysis (CCA) Feature extraction

5) Quantitative method of SSVEP color vision: Inducing SSVEP and CCA response value for 27 gradients respectively, drawing the CCA value-brightness ratio curve, and obtaining the brightness ratio corresponding to the lowest value of CCA value, which is the iso-brightness point; through the serious color vision Degree I _CVD objective indicators to judge the results of color vision EEG examination;

6) Color vision test result feedback: After completing all stimulation paradigms, the user's objective EEG color vision test results are output on the screen.

The step 5) SSVEP color vision quantitative method is specifically:

Red-green CIE XYZ color chromaticity information is converted into cone LMS color space: red (L _red , M _red , S _red ) and green (L _green , _M green, S _green ), due to the contribution of S-shaped cones to brightness It is very small, so it is ignored; the red and green objective isoluminance points are expressed as:

——The brightness information value produced by the red square on the L-shaped cone;

——The brightness information value produced by the red square on the M-type cone;

——The brightness information value produced by the green square to the L-shaped cone;

——The brightness information value produced by the green square to the M-type cone;

By calculation, normal color vision theory objectivity luminance point T _normally 0.50; if the color perception of red blind, luminance information value L type cone cells is negligible, then T _protanopia 0.68; Similarly, if the color vision of green color blindness, Neglecting the brightness information value generated by the M-type cone cells, T _deuteranopia is 0.43; the red-weak isoluminescence point T _red-weak and the green weak iso-luminance point T _green-weak are between normal and protanopia and deuteranopia, etc. Between brightness points:

T _protanopia >T _{weak red} >T _normal >T _{weak green} >T _{green blind} (2)

The SSVEP test the luminance and the like of the user and the _user point T other luminance normal theoretical point of _normal T expressed as a difference of color vision _users deviation D:

D _user =|T _user- T _normal | (3)

The difference between the brightness points of _red and deuteranopia, T _{red blindness} and T _{green blindness,} and T _normal is expressed as color blindness deviation D _{color blindness} :

So, the severity of color vision I _CVD feel deviation D _users with color blindness deviation D _{color blindness} color is represented by:

The 27 gradients were induced to SSVEP and CCA response values were performed, and the CCA value-brightness ratio curve was drawn to obtain the brightness ratio corresponding to the lowest value of the CCA value, which is the iso-brightness point; through the above calculation of the severity of sensation I _CVD , and Combine with the _{user of} iso-brightness point T, according to the table below to get the degree and type of brightness

I CVD	T user	Color vision
<20%	——	normal
20%-40%	T user >0.50	Light red weak
To	T user <0.50	Light green weak
40%-60%	T user >0.50	Moderate red weak
To	T user <0.50	Moderate green weak
60%—80%	T user >0.50	Severe red weak
To	T user <0.50	Severe green weak
80%—100%	T user >0.50	Protanopia
To	T user <0.50	Green blindness

Correspondingly, the present invention also provides a color vision function inspection system based on visual evoked potential, including:

The reference electrode, ground electrode, and measurement electrode;

The EEG acquisition module is connected to each electrode, after amplification, filtering, and digital-to-analog conversion, the EEG signal is output to the computer for further data processing, thus forming a brain-computer interface platform;

A computer with the built-in red-green flip stimulus paradigm, and the processing process includes: stimulus paradigm red-green brightness ratio gradient, stimulus paradigm presentation and SSVEP color vision quantification;

The display device, after the computer completes all stimulus paradigms, outputs the user's objective EEG color vision test results on the screen.

The beneficial effects of the present invention are:

The present invention proposes a color vision function inspection method based on visual evoked potentials, which is simple and quick to operate, solves the problem that traditional color vision inspection is not objective enough and difficult to quantify, is not suitable for patients with communication difficulties and forensic identification, and shows the following advantages:

(1) The design of the present invention is based on the red-green flip SSVEP paradigm, combining the brightness ratio gradient with color vision inspection, starting from the color mechanism and brightness mechanism of human visual information processing, and does not rely on subjective judgments, and has objectivity.

(2) The present invention proposes the color vision degree index I _CVD value and the isoluminance point T value, which can quantitatively analyze the color vision degree and determine the degree of color weakness and color blindness.

Description of the drawings

Figure 1 is a typical red-green brightness contrast gradient stimulus pattern (brightness ratio T = 0.0, 0.43, 0.50, 0.68, 1.0).

Figure 2 shows the brain-computer interface platform of the present invention.

Figure 3 is a layout diagram of EEG electrodes of the present invention.

Figure 4 shows the CCA value-red and green brightness contrast gradient curve of normal color vision.

Figure 5 shows the EEG response CCA value-red and green brightness contrast gradient curve of protanopia.

Figure 6 shows the CCA value of the EEG response of the green blindness-the contrast gradient curve of red and green brightness.

Figure 7 shows the CCA value of the weak red EEG response-the contrast gradient curve of red and green brightness.

Figure 8 shows the weak green EEG response CCA value-red and green brightness contrast gradient curve.

Figure 9 shows the correlation between the Icvd value and the TES of the FM100 color check result.

Detailed ways

The present invention will be described in detail below with reference to the drawings.

The color vision function inspection method based on visual evoked potential includes the following steps:

1) Red and green flip stimulus paradigm: Using the mode flip SSVEP method in the brain-computer interface, the periodic flip presentation of the paradigm pattern texture is drawn through MATLAB using Psychophysics Toolbox programming, which can stabilize the stimulation and induce SSVEP; refer to Figure 1, the performance of the sports stimulation target The red and green squares are alternately arranged. The red squares and the green squares are equal in size, with the same number, and alternately arranged; during the stimulus presentation process, the overall brightness and overall size of the paradigm remain unchanged; the flip frequency of the paradigm is defined as the stimulation frequency, the paradigm The pattern changes twice in one cycle;

2) Stimulus paradigm red-green brightness ratio gradient: to ensure the red-green chromaticity information (CIE XYZ color space: x _red = 0.628, y _red = 0.337; x _green = 0.349, y _green = 0.590) and the total brightness remains unchanged and changed Stimulus paradigm red-green brightness ratio T, T is the ratio of red brightness to total brightness:

Lu _red -the brightness of the red square;

Lu _green -the brightness of the green square;

Referring to Figure 1, the ratios of red to total brightness in red and green are respectively 0, 0.1, 0.2, 0.3, 0.4, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.52, 0.54, 0.56, 27 gradients such as 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.7, 0.8, 0.9 and 1.0;

3) Brain-computer interface platform construction: Refer to Figure 2 and Figure 3. Before the experiment, the electrodes were arranged according to the 10/20 system method. Before the experiment, the reference electrode was placed on the subject's left earlobe A1, and the ground electrode was placed on the subject's forehead Fpz , The measuring electrodes are arranged in the occipital area of the head (PO3, PO4, POz, O1, O2, Oz), and conductive paste is injected into each measuring electrode to ensure good contact between the electrodes and the scalp; the electrodes are connected to the EEG acquisition module, After filtering and digital-to-analog conversion, the EEG signal is output to the computer for further data processing;

4) Presentation of stimulus paradigm: The computer expands the display to present the stimulus paradigm on the high refresh rate display; during the experiment, the user needs to follow the screen prompts to watch the stimulus paradigm; during the experiment, the subject needs to sit quietly and not be disturbed In the laboratory, each time a binocular test is performed; the EEG signal generated when the user is looking at the paradigm is collected by EEG acquisition equipment, and after amplification, filtering and A/D conversion, the processed EEG signal is input into the computer using typical Correlation analysis (CCA) for feature extraction;

5) SSVEP color vision quantitative method: red-green CIE XYZ color chromaticity information is converted into cone LMS color space: red (L _red , M _red , S _red ) and green (L _green , M _green , S _green ), because of S Type cone cells contribute little to the brightness, so they are ignored; the red and green objective isoluminance points can be expressed as:

——The brightness information value produced by the red square on the L-shaped cone;

——The brightness information value produced by the red square on the M-type cone;

——The brightness information value produced by the green square to the L-shaped cone;

——The brightness information value produced by the green square to the M-type cone;

By calculation, normal color vision theory objectivity luminance point T _normally 0.50; if the color perception of red blind, luminance information value L type cone cells is negligible, then T _protanopia 0.68; Similarly, if the color vision of green color blindness, Neglecting the brightness information value generated by the M-type cone cells, T _deuteranopia is 0.43; the red-weak isoluminescence point T _red-weak and the green weak iso-luminance point T _green-weak are between normal and protanopia and deuteranopia, etc. Between brightness points:

T _protanopia >T _{weak red} >T _normal >T _{weak green} >T _{green blind} (3)

The SSVEP test the luminance and the like of the user and the _user point T other luminance normal theoretical point of _normal T expressed as a difference of color vision _users deviation D:

D _user =|T _user- T _normal | (4)

The difference between the brightness points of _red and deuteranopia, T _{red blindness} and T _{green blindness,} and T _normal is expressed as color blindness deviation D _{color blindness} :

So, the severity of the color vision of color vision can I _CVD deviation D _users with color blindness _{color blindness} to represent the deviation D:

Referring to Figures 4-8, 27 gradients were induced to SSVEP and CCA response values were performed, and the CCA value-brightness ratio curve was drawn to obtain the brightness ratio corresponding to the lowest value of the CCA value, which is the isoluminance point. Through the above calculation of the severity of sensation I _CVD and combining with the _{user of the} isoluminescence point T, the degree and type of sensation can be obtained according to the following table,

I CVD	T user	Color vision
<20%	——	normal
20%-40%	T user >0.50	Light red weak
To	T user <0.50	Light green weak
40%-60%	T user >0.50	Moderate red weak
To	T user <0.50	Moderate green weak
60%—80%	T user >0.50	Severe red weak
To	T user <0.50	Severe green weak
80%—100%	T user >0.50	Protanopia
To	T user <0.50	Green blindness

6) Color vision test result feedback: After completing all stimulus paradigms, after CCA feature extraction and SSVEP color vision quantitative calculation method, the user's objective EEG color vision test results are output on the screen.

The present invention will be described below in conjunction with embodiments.

The above experiment was performed on 17 subjects (7 with normal color vision, 2 with weak red, 4 weak with green, 1 protanopia, and 3 deuteranopia). Follow the above step 3) to install electrodes and build the brain -Machine interface platform, according to the above step 4) for paradigm presentation, EEG signal acquisition and feature extraction. According to the above step 5), referring to Figure 4-8, draw the CCA value-brightness ratio curve to obtain the brightness ratio corresponding to the lowest value of the CCA value, which is the iso-brightness point. EEG signal analysis and objective EEG color vision test results were determined, and it was found that the EEG objective color vision test results were consistent with the subjects' color vision. The subjective psychophysical color vision of the above subjects was quantitatively checked through the FM100 color chess system. The overall error of FM100 was analyzed by linear fitting between TES and ICVD. Refer to Figure 9 and found that the effect is good (r=0.870).

The invention can objectively and quantitatively detect the color vision function of the user, establishes a good correlation with the subjective psychophysical examination, and realizes the objective detection of the color vision function of special users such as infants, pre-linguistic children, and forensic examinees. means. The color vision function inspection method based on visual evoked potential is convenient, fast, objective and quantitative, and has a good practical prospect.

Claims (2)

1. The color vision function inspection method based on visual evoked potential is characterized in that it comprises the following steps:

   1) Red and green flip stimulus paradigm: using the mode flip SSVEP method in the brain-computer interface, the periodic flip presentation of the paradigm pattern texture is drawn through MATLAB using Psychophysics Toolbox programming, which can stabilize the stimulus and induce SSVEP; the sports stimulus target appears as alternate red The green squares, red squares and green squares are equal in size, same in number, and arranged alternately; during the stimulus presentation process, the overall brightness and overall size of the paradigm remain unchanged; the flip frequency of the paradigm is defined as the stimulus frequency, and the pattern of the paradigm is in a cycle Changed twice within;

   2) Stimulus paradigm red-green brightness ratio gradient: to ensure that the red-green chromaticity information and total brightness remain unchanged, change the red-green brightness ratio of the stimulus paradigm so that the ratio of red to total brightness in red and green is 0,0.1,0.2, 0.3, 0.4, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.7, 0.8, 0.9 and 1.0 total 27 gradient;

   3) Construction of brain-computer interface platform: Before the experiment, the reference electrode was placed on the subject’s left earlobe, the ground electrode was placed on the subject’s forehead, and the measurement electrode was placed on the occipital area of the head; the electrode was connected to the EEG acquisition module, and enlarged , After filtering, digital-to-analog conversion, output EEG signals to the computer for further data processing;

   4) Presentation of the stimulus paradigm: The computer expands the display to present the stimulus paradigm on the high refresh rate display; during the experiment, the user needs to follow the screen prompts to watch the stimulus paradigm; during the experiment, the subject needs to sit in the laboratory every time Perform binocular test once; collect the EEG signal generated when the user is looking at the paradigm through EEG acquisition equipment, after amplifying, filtering and A/D conversion, input the processed EEG signal into the computer and use canonical correlation analysis (CCA) Feature extraction

   5) Quantitative method of SSVEP color vision: Inducing SSVEP and CCA response value for 27 gradients respectively, drawing the CCA value-brightness ratio curve, and obtaining the brightness ratio corresponding to the lowest value of CCA value, which is the iso-brightness point; through the serious color vision Degree I _CVD objective indicators to judge the results of color vision EEG examination;

   6) Color vision test result feedback: After completing all stimulation paradigms, the user's objective EEG color vision test results are output on the screen.
2. The color vision function inspection method based on visual evoked potentials according to claim 1, wherein said step 5) SSVEP color vision quantitative method is specifically:

   Red-green CIE XYZ color chromaticity information is converted into cone LMS color space: red (L _red , M _red , S _red ) and green (L _green , _M green, S _green ), due to the contribution of S-shaped cones to brightness It is very small, so it is ignored; the red and green objective isoluminance points are expressed as:

   

   

   ——The brightness information value produced by the red square on the L-shaped cone;

   

   ——The brightness information value produced by the red square on the M-type cone;

   

   ——The brightness information value produced by the green square to the L-shaped cone;

   

   ——The brightness information value produced by the green square to the M-type cone;

   By calculation, normal color vision theory objectivity luminance point T _normally 0.50; if the color perception of red blind, luminance information value L type cone cells is negligible, then T _protanopia 0.68; Similarly, if the color vision of green color blindness, Neglecting the brightness information value generated by the M-type cone cells, T _deuteranopia is 0.43; the red-weak isoluminescence point T _red-weak and the green weak iso-luminance point T _green-weak are between normal and protanopia and deuteranopia, etc. Between brightness points:

   T _protanopia >T _{weak red} >T _normal >T _{weak green} >T _{green blind} (3)

   The SSVEP test the luminance and the like of the user and the _user point T other luminance normal theoretical point of _normal T expressed as a difference of color vision _users deviation D:

   D _user =|T _user- T _normal | (4)

   The difference between the brightness points of _red and deuteranopia, T _{red blindness} and T _{green blindness,} and T _normal is expressed as color blindness deviation D _{color blindness} :

   

   So, the severity of color vision I _CVD feel deviation D _users with color blindness deviation D _{color blindness} color is represented by:

   

   The 27 gradients were induced to SSVEP and CCA response values were performed, and the CCA value-brightness ratio curve was drawn to obtain the brightness ratio corresponding to the lowest value of the CCA value, which is the iso-brightness point; through the above calculation of the severity of sensation I _CVD , and In combination with the _{user of the} isoluminescence point T, the degree and type of color perception are obtained according to the following standards: if the I _CVD value is less than 20%, it means that the color vision is normal; if the I _CVD value is greater than 20% but less than 40%, it means that the color is weak; If the I _CVD value is greater than 40% but less than 60%, it indicates moderate color weakness; if the I _CVD value is greater than 60% but less than 80%, it indicates severe color weakness; if the I _CVD value is greater than 80%, it indicates color blindness; at the same time, color vision The type of defect patient can be judged by T _user . If T _{user is} greater than 0.50, it means red color vision defect; if T _{user is} less than 0.50, it means green color vision defect.

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