DE102008053015B3 - Color-channel-selective stimulation process for visual system involves targeted selected tapping stimulation with glance follow-up - Google Patents

Abstract

The color-channel-selective stimulation process involves targeted selected tapping stimulation, preferably by the image double energy analyzer silent substitution (SST) method, combined with glance follow-up. This should ideally operate without being touched and without the need for calibration, and compensates for the angle-dependent spectral properties of the stimulator.

Description

The The present invention relates to a method and an associated device for stimulating the visual system of a patient according to the principle the silent substitution technique while capturing the Viewing direction of the patient for tracking the stimuli.

For functional examination of the visual system, a variety of diagnostic approaches are known. In addition to various subjective procedures, electrophysiological examination methods have become established in the field of objective diagnostics (cf. WO2000035344A1 . WO2000016690A3 . DE19824626A1 . WO1999058046A1 ). To obtain diagnostic parameters exist various stimulation paradigms, the z. B. be realized via flash or pattern stimulation. In this case, different colors or wavelengths are used, wherein the application to the eye by projection systems or light sources takes place. With conventional monochrome stimuli, however, it is not possible to make detailed statements about the function of the individual color processing channels. The eye cells of the eye continue to exhibit various physiological and electrochemical differences, which result in specific vulnerabilities to various clinical pictures. To make this diagnostically usable, a special stimulation principle is necessary, which is called Silent Substitution Technique (SST). By suitable application of the SST principle, there is the possibility of targeted irritation of individual color channels of the eye. During SST stimulation, the position of the stimuli to the site of action on the retina must be kept constant during the entire examination. The patient is prompted to fixate on a fixed point, which, however, requires his active participation and as a result leads to fatigue and involuntary eye movements. In addition, depending on the clinical picture and condition of the patient, an active fixation by the patient may become impossible. The quality of the physiological data obtained parallel to the stimulation is thereby negatively influenced. The subsequent diagnosis is endangered in its validity and may entail higher examination and follow-up costs (eg due to multiple examinations and false diagnoses).

task The present invention is therefore a method and a associated Device for stimulating the visual system of a patient according to the principle of silent substitution technique at the same time Acquisition of the line of vision of the patient for tracking the patient Provide stimuli that improve the quality of the examination results with simultaneous reduction of the resulting examination and Follow-up costs can be increased.

According to the invention succeeds the solution This object with the features of the first and the ninth claim. Advantageous embodiments of the solution according to the invention are specified in the subclaims.

The The invention is explained in more detail below with reference to drawings. It demonstrate:

1 - Schematic representation of the method according to the invention

2 - Principle embodiment of the device according to the invention

The The present invention describes color channel selective stimulation of the visual system using a look-ahead silent substitution technique using a spectral compensation method. A view guided SST stimulation, which captures the eye movements and the color channel-selective stimulus pattern at the same time nachfährt, can compensate for the disadvantages presented. The for the application a look-behind necessary size Stimulator / screen size currently being used for example by Liquid Crystal Display (LCD), Light Emitting Diodes in combination with LCD (LED-LCD) or Liquid Crystal realized on silicon (LCoS) technology. These technologies show however, significant angle dependencies in their spectral properties, showing the SST stimulation in Function and effectiveness severely restrict. To the solution the result of the novel combination of SST and Blicknachführung Problems come a newly developed integrative compensation method for use. This creates the possibility of any type of visual interior of the human eye deliberately selective and with fixed local reference to stimulate on the retina.

Glide-directed stimulation technique

In order to achieve a precise assignment of stimuli to their positions in the visual field during a visual stimulation, the method of focusing on a predetermined fixation point is generally used (cf. JP3092135AA ). The fixation on a fixed point is very strenuous and tiring or sometimes not possible especially over a longer period of time. In the course of the examination, involuntary eye movements occur which make it impossible to determine the location of the stimuli.

• – Elektrookulographie (EOG) basiert,
• – durch sklerale Kontaktlinsen bzw. Suchspulen,
• – mittels Photookulographie (POG) bzw. Videookulographie (VOG) und
• – vollständig videobasierte Verfahren, welche Bilder der Pupille und des Korneareflexes auswerten.

Another possibility for establishing this location reference is the use of a system for detecting the viewing direction of the human eye. A single stimulus or a stimulus Onsmuster can then be projected through a connected stimulation system relative to the mobile viewpoint. In general, devices for measuring eye movement can be divided into two groups: devices that measure the eye position relative to the head and systems that determine the orientation of the eye in space. This orientation is also referred to as point of view, sight line or viewing direction (POR). Looking at the different methods of measurement, a subdivision into four categories is possible:

• - electrooculography (EOG) based,
• By scleral contact lenses or search coils,
• By means of photookulography (POG) or videoculography (VOG) and
• Fully video-based methods that evaluate images of the pupil and corneal reflex.

In principle, however, other methods are conceivable. The first two methods allow only insufficient accuracy, do not work contactless and can only determine eye movement relative to the head. By way of example, a conversion by means of coils should be mentioned ( DE 10351928A1 ), which seems particularly suitable for applications in MRI scanners. The solution presented here deals very precisely with the inductive determination of the viewing direction, but does not look closer to the parallel visual stimulation. In addition, it is proposed to use a commercial stimulator device (type: "Silent Vision" manufacturer AVOTEC), which is also subject to the spectral dependencies described above, but for which no compensation methods are specified.

By contrast, POG and VOG methods are non-invasive since only image information is evaluated here. The basis is the recognition of various features of the eye during rotation and translation. These include, among other things, the variable shape of the pupil image, the position of the limbus (border between the iris and sclera) and various corneal reflexes. The reflexes are caused by a mostly infrared point light source placed near the eye. However, fixation of the head is also necessary in these systems. Another crucial disadvantage is the binding to the video standard with a fixed frame rate of 25 / s. For many fast eye movements, the resulting temporal resolution is insufficient. Devices of the fourth category generally use infrared illumination to generate special grain reflexes (Purkinje images), which are subsequently evaluated by means of image processing algorithms. Here, both the focus of the pupil and the light reflex itself is determined. The position of the two features relative to one another can be used to determine the line of sight vector. This is from the EP1201181A1 a method is known which uses a conventional, spectrally uncorrected light source for generating the stimuli, wherein their lighting parameters are not discussed. In addition, no implementations regarding a selective color channel stimulation are explained. However, all these methods require calibration of the systems. This is done by carefully looking at nine or fifteen points on the stimulator. Thus, the accuracy depends strongly on the cooperation of the subject. For use on patients this should be considered critical. In an advantageous embodiment, therefore, a two-camera viewing direction detection system (Eyetracker) is described, which operates without contact and calibration free (see. WO2003065886A1 . DE10144580A1 . EP1809163A1 . US20030125638A1 ). One camera captures one image of the eye from two spatial directions. Since the stimulation of the visual system occurs in the visible range of the electromagnetic spectrum, the illumination for the viewing direction detection takes place in the infrared range. An interface is used to transfer the two camera pictures or their reduced sections to a PC. Using image processing methods, the generation of binary images is then carried out, which contain only the pupils. From these, the contours of the pupils are calculated. Due to the known distances and angles between the patient's eye and the camera, the determination of the line of sight vector takes place via further processing steps. In this way you get the current focus on the stimulator. The stimulation pattern can now be shifted so that its center lies on the viewpoint. Although the solutions mentioned mention the possibility of computer-controlled influencing of the brightness and color of the stimuli (cf. DE10144580A1 ), but neither the principles of SST, nor a solution to the spectral dependencies that occur. The proposed stimulators (referred to herein as light-distributors) are subject to these dependencies, but are not further classified and described spectrally.

Furthermore, methods for determining the direction of sight are known from the prior art ( DE 195053399A1 . US2007 / 0146637A1 ), which can not be clearly classified in the presented classification. Rather, combinations of the above methods are used here or used with different objectives. In the DE19505399A1 For example, a method for visual field examination by analyzing eye movement is described. It is proposed to use in principle one of the above-mentioned methods, wherein colored test points (stimuli) with different color composition and saturation can be used. A reference to the color However, channel-selective stimulation and the problems resulting from gaze tracking are not produced. In the US2007 / 0146637A1 A general assessment of stimuli based on parallel views is described. The central question is how a change in the stimuli affects the observer. The core of the invention is therefore the interpretation of the gaze data in a so-called "Eye Interpretation Engine". Areas of application are the human-machine interface, media and advertising research as well as the games industry. The technical implementation of the stimuli is not discussed in more detail in this patent. It is merely an indication that they can be generated by Cathode Ray Tubes (CRT) or LCDs. A methodological consideration for the use of the erfindungemäßen solution in elektrodiagnostischen environment or for selective color channel stimulation is not performed.

Silent Substitution Technique (SST)

Already in the 17th century, the connection between color vision disorders and eye diseases was recognized first generalized by Köllner at the beginning of the 20th century has been. Considering the origin of color vision at the cellular level, the visual sensory cell types of the eye differ (L-, M-, S-Cones; German -Zapfen) u. a. in calcium metabolism, in membrane permeability as well in number and distribution on the retina. In addition, there are differences in the course of the phototransduction cascade, which is the transformation of the absorbed light quantum into bioelectric signals controls. from that there are specific vulnerabilities to different diseases, which can be used diagnostically by means of suitable stimulation technology can be made. Over the past two decades, the focus has been on the use of Color Perimeters for the detection of visual disturbances, for example caused by glaucoma or optical neuropathies. A common method here is the use of a colored Background. This should be the sensitivity of two pin types reduce, with one stimulation field exciting the remaining type. The mechanism described uses the blue-on-yellow perimetry. Several studies and. a. by M.P. Simunovic et al. ("How well does color perimetry isolate responses from individual cone mechanisms? "J. Glaucoma., vol. 13, no. 1, pp. 22-27 Feb. 2004) showed that so only a partially isolated S-pin irritation succeed.

Around but on the one hand arbitrary pin and this other hand, completely selective to stimulate, is the use of a methodically more complex stimulation principle necessary. The SST represents such a principle and allows it depending on the implementation, to meet both conditions. An early work on the possible Application in the field of electro-diagnostic examination The visual system was designed by O. Estevez and hH. Spekreijse published ( "The silent substitution method in visual research "Vision res., vol. 22, no. 6, pp. 681-691, 1982). Generalizing it can be stated that this is due to a specially adapted stimulation sequence is realized, the stimulates only the one or the too sensitive sensory cell types. All other non-irritating cell types, but the stimulus also achieved, can do not perceive this. As a result, they do not contribute to the resulting response signal and are referred to as "silent".

in the Essentially, there are three different SST-based stimulation methods today known. In heterochromatic flicker photometry (HFP) (must the patient first an individual and subjective color balance between two Realize light sources. The adjustment takes place at frequencies above of 30 Hz, the actual stimulation subsequently at stimulation frequencies below of 5 Hz. Due to the different temporal resolution of the Pin types, in conjunction with an additional adaptation background, a selective color channel stimulation can be achieved. Has a disadvantage the subjective nature of the color balance turns into one incomplete Lead pin replacement can. Added to this are the increased time requirements for one Measurement and the necessary repetitions, to achieve a significant color balance.

An exemplary impact model based approach is described in the work of DC Hood et al. ("The multifocal visual evoked potential and cone-isolating stimuli: implications for L-to M-cone ratios and normalization" J. Vis., Vol. 2, no. 2, pp. 178-189, 2002). The basis for the implementation of the SST are special cone sensitivity curves (cone fundamentals). Based on the emission spectrum of a stimulator, these curves can be used to calculate the absorbed quantum number for each pin type. Thus, it is possible to create a stimulation sequence in which the absorbed quantum number of all unimaginable pin types remains constant. The latter thus do not contribute to the response signal ("silent"). However, the methodology lacks the implementation of a direct linkage of the model with other color spaces in which, for example, the stimulator used and / or its stimulus can be characterized and compared. In our own work, an alternative impact model for the application of the SST principle has been developed. The chosen approach according to RWG Hunt (Measuring color, Ellis Horwood series in applied science and industrial technology ed. London: Ellis Horwood, 1995) allows both a transition into the biological working plane of the cones (LMS space), as well as a link in the standardized standard color space of the CIE realize (XYZ space). The necessary steps can be found in the work of S. Klee, P. Bessler, P. Husar, G. Henning and F. Schlegelmilch ("Investigation of spectral distribution and dynamics of stimulators for selective cone excitation" in IFMBE Proceedings Prague: IFMBE Proceedings, 2005; "IFMBE Proceedings, 2005; Methodological and Experimental Investigations for the Implementation of Electrophysiological Blue-Channel Stimulation". Ilmenau University of Technology, 2005; Institute of Biomedical Engineering and Computer Science, 2004). Hunt's biological activity curves also allow the exact calculation of the amount of absorbed radiation (quantum absorption) per unit area and cone type of the retina. This is called activation. Access to the XYZ room, for example, allows the direct determination of color, color and white value. A calibration of the stimulator colors and the adjustment to a standard illuminant are also possible. In addition, the technical RGB space of the stimulator, which results, for example, from the control by means of PC and graphics card, was integrated into the model. The stimulator can now be any displays or projectors that can be controlled via a graphics card. Further connections of stimulators and control units are possible in principle. By programming the graphics card, which corresponds to a change in the RGB space, the photometric parameters and thus also the stimulus to be applied can be influenced. Its location in standard color space and its effect on the biological level also change, both being captured by the developed model. As a result of an exemplary application, by directly driving the stimulator for each selected stimulus, the resulting activation of the individual pin types can be calculated. It is both an exact characterization of stimulator, stimulus and biological effect, as well as the development of stimulation sequences that cause a targeted color channel irritation, possible. Based on the described adaptations of the SST principle with respect to the stimulator's properties and the biological effect in the eye, the overall concept of the stimulation is referred to hereafter as Ilmenau Display and Eye Adapted-Silent Substitution Technique (IDEA-SST).

The present invention proposes a method and a device which enables and combines the correct function of the combination of the two principles shown. Here, the present invention clearly differs from the prior art ( DE10351928A1 . EP1201181A1 . DE10144580A1 . WO2003065886A1 . EP1809163A1 . US20030125638A1 . DE19505399A1 . US20070146637A1 ). So far, only the reactions of the gaze detection and partly their connection with an analysis of parallel obtained data of the visual system have been treated, but is not discussed on the use for a selective color channel stimulation, nor on resulting spectral problems. Their necessary solution in the combination of gaze tracking and selective color channel stimulation is not recognizable and will be presented below.

The inventive method combines the possibilities a targeted, selective spiked stimulation, preferably is realized by the IDEA-SST, with a Blicknachführung, the ideally contactless and works without calibration. Any other combination SST-based stimulation and glaucous pacing is however also conceivable.

The combination of these principles results in problems whose solution is essential for a correct mode of action. The necessary for the realization of a complete color channel selective stimulation SST, is coupled to the knowledge of the spectral properties of the stimulator. These determine the composition of the SST stimuli. After calculation of the SST stimulation sequence, any change in the spectral distribution function would result in incomplete and unselective stimulation of the pin system. The large stimulator area / image diagonal required for the application of a gaze tracking is currently being realized with LCD, LED-LCD or LCoS technology. Typical image diagonals of CRT stimulators (around 20 '') can not be used for this purpose with regard to a minimum distance to the patient's eye to be observed. The stimulator itself must be freely controllable, so as to ensure any displacement of the stimulation pattern. The techniques listed, however, show a pronounced viewing angle dependency, which is evident in a change in the spectral properties along the presentation site (on the stimulator). With increasing distance from the center and thus increasing eccentricity, the changes increase. It could be shown in own investigations that this characteristic shows an additional horizontal and vertical directional dependence. If the effects were not determined and corrected, the unselective stimulation described above would be the direct consequence. The method according to the invention therefore comprises a method for compensating the angle-dependent spectral properties presented. For this purpose, the spectral distribution is initially determined for the center of the stimulator by means of a radio spectrometer determined function. Subsequently, the angle-dependent change of the distribution function is determined horizontally and vertically with a sufficiently high angular resolution in the direction of the periphery. In this case, a measuring system with solid angle reference is to be used and scattered light components optionally to be minimized by introducing additional apertures. The so-measured main axes of the stimulator divide this into four quadrants. In the squares themselves the measurements have to be repeated. At the same time, the measuring point density in the periphery should increase. Between these points, a suitable interpolation is then implemented to replace missing data. From the angle-dependent distribution functions thus determined, an error amount related to the initial measurement in the center is calculated for each wavelength and each location. Preferably, all calculated values are to be stored in an error matrix. A suitable inversion of the matrix and its connection to the stimulation sequence thus gives the possibility of adapting the composition of the SST stimuli to the stimulator, depending on the place of presentation. The problem described, which would normally lead to unselective irritation of the pin system and thus to misdiagnosis, can thus be solved. Consequently, it is possible with the method according to the invention to selectively stimulate any type of visual inner cell of the human eye selectively and with fixed local reference to the retina. The necessary compensation of the location-dependent or angle-dependent spectral properties is realized with an integrative method.

The inventive method is in principle in 1 shown. The SST stimulation sequence necessary for the selectively stimulable visual sensory cells ( 1 ) is first used for the stimulator ( 3 ).

Subsequently, its activation ( 2 ), wherein the applied sequence in the patient's eye ( 4 ) achieves the desired selective effect. If the patient changes his line of sight, this is achieved through the eye-tracking system ( 5 ) detected. The data of the gaze coordinates are the spectral compensation unit ( 6 ) and serve the spectral compensation as a basis for adapting the SST stimulation sequence. At the determined viewpoint, the adapted stimulation sequence is now presented. The desired selective color channel irritation and the described diagnostic advantages are retained.

to Application of the stimuli serves, for example, a freely programmable Display. All other arbitrary displays or projection systems can also be used. The stimulation pattern for color channel selective Irritation of the visual system can be sufficiently fast to the gaze of the Followed up patients become. Involuntary eye movements while the investigation will be balanced. The need for a tiresome Fixation to a fixed point of the stimulator no longer exists. Both the stimulation of a defined area on the retina, as well as its selective color channel irritation, is characterized by this novel Procedure over the entire examination time ensured.

An exemplary construction of the device according to the invention is 2 refer to. The functionality is provided here by two networked control units. One unit realizes the eye tracking ( 8th ), whereby the data of any eye-tracking module ( 10 ) be evaluated. The gaze detection module may include, among other things, one or more cameras that may be coupled to a particular lighting unit. Other methods for detecting the line of vision (eg, optical, electrical, mechanical, magnetic, electromagnetic, acoustic, bioelectrical or biomagnetic, etc.) may also be used. The control unit for realizing the gaze tracking ( 8th ) as well as the eye-tracking module ( 10 ) can also be integrated in a single system (eg FPGA, single-board computer).

The second control unit ( 9 ) sets the special SST stimulation sequence ( 1 ) with the help of any stimulator ( 3 ) around. This is ideally optimized for the application and freely programmable. Any other type of display or projection system is conceivable here. By networking the two control units, the SST stimulus can be calculated taking into account the determined gaze data ( 11 ) be tracked sufficiently fast. The necessary spectral compensation as a function of the new presentation location, can either in the control unit for generating the stimulation sequence ( 9 ) or in an upstream system. The two control units ( 8th ) and ( 9 ) as well as the eye-tracking module ( 10 ) are also realizable again in a single system. Furthermore, an embodiment which allows all necessary processing steps directly in the stimulator without additional external control computer, also conceivable. In addition, any other combinations of the illustrated functional units are possible. Furthermore, a signal acquisition and evaluation unit ( 7 ), on which, for example, the stimulation can be monitored or biological data obtained in parallel can be stored. The biological response signals obtained in parallel can be measured using various methods (eg, EEG, MEG, MRI, PET, etc.) with sensors (eg, any ERG electrodes, multichannel ERG electrodes, electrode arrays, EEG electrodes, first-order electrodes, electrodes second type, magnetic sensors, etc.) and can subsequently by various Signalverarbei evaluation algorithms (eg in the time, frequency or time-frequency domain or analysis methods such as component decomposition, averaging, ICA, PCA, PARAFAC, matching pursuit or source reconstruction algorithms).

With The disclosed invention is an objective targeted stimulation and examination of visual nerve cells of the eye possible. An integration of the device according to the invention in existing diagnostic devices (eg structurally: US, MRI, CT, optical imaging, cameras, etc. or functional: vessels, metabolism, molecular imaging, electrical and magnetic derivatives, EEG, MEG, fMRI, PET, SPECT, NIRS, etc.) or in any therapy devices is here also possible.

1

SST stimulation sequence

2

Stimulatoransteuerung

3

stimulator

4

patient's eye

5

Eye tracking system

6

spectral compensation unit

7

signal detection and evaluation unit

8th

control unit for the realization of the Blicknachführung

9

control unit to generate a stimulation sequence

10

Eye tracking module

11

identified view data

Claims (12)

Method for stimulating the visual system of a patient according to the principle of the silent substitution technique, in which at the same time the line of sight of the patient for tracking the stimuli is detected, characterized in that the spectral adjustment of these SST stimuli depending on the presentation on the stimulator whose viewing angle-dependent Spectral properties can be compensated by linking the respective stimulation sequence with a previously determined from the viewing angle-dependent spectral distribution functions error matrix. Method according to claim 1, characterized that the visual system is magnetic, electric or electromagnetic is stimulated with a silent substitution technique. Method according to claim 1 or 2, characterized that the determination of the line of sight online or offline means Any detection systems is realized. Method according to claim 3, characterized that one or more cameras in any technological design for Determining the line of sight can be used. Method according to one of Claims 1 to 4, characterized that generates the stimuli with any light and radiation modulators become. Method according to one of claims 1 to 5, characterized that method for improving the signal-to-noise ratio be used. Method according to one of Claims 1 to 6, characterized that the creation of stimulation sequences, stimulation and their control and evaluation of the data obtained with mathematical Transformation process is realized. Method according to one of claims 1 to 7, characterized that different evaluation and analysis methods in time, frequency or time frequency space are used. Device for stimulating the visual system with a method according to one of claims 1 to 8, comprising: - a control unit ( 9 ) for generating the stimulation sequence ( 1 ) - a stimulator ( 3 ) for reproducing the generated stimuli - a gaze detection module ( 10 ) for determining the viewing direction - a control unit ( 8th ) for the realization of the gaze tracking and - a signal acquisition and evaluation unit ( 7 ) to control and monitor the stimulation. Device according to claim 9, characterized that any sensors for the derivation of physiological stimulus response signals are provided. Device according to claim 9 or 10, characterized that it can be integrated in any diagnostic equipment. Device according to one of claims 9 to 11, characterized that they are used in combination with any therapy devices becomes.