Technical field

The invention relates to an ophthalmic diagnostic apparatus comprising means of illumination, an optical unit, a sensing unit and an electronic unit.

The invention further relates to a method of operation of the ophthalmic diagnostic apparatus, in which an image of the retina and/or the iris of the patient ^' s eye is obtained.

Backgound art

Biometric identification of people is carried out by various methods based on sensing different biometric parameters of an identified person. It is important for the sensed biometric parameters or their combinations to ensure sufficient uniqueness of the parameters sensed and thus to enable sufficient reliability in establishing the identity of the examined person, for example for the purpose of access rights of persons to enter premises or their parts, access rights to various systems, etc.

One of the biometric parameters which allows a relatively reliable identification of a person is an identification based on sensing the iris and/or the retina of the human eye, which, if both parameters are combined, i.e. sensing both the iris and the retina of the human eye, enables a very safe and reliable identification of the examined person. This is generally known, for example, from WO2006047002A1.

US 2011/0285836 A1 discloses a multimodal biometric identification system capturing and processing images of the iris and the retina for biometric identification. US 2011/0285836 A1 further describes a multimodal ocular identification system which captures and processes images of iris or retina from both eyes of the subject. According to US 2011/0285836 A1 biometrics based on the data provided by these systems is more accurate and robust than biometrics using the biometric data which include data only from the iris or only from the retina, and - in both cases - only of a single eye. The apparatus according to US 2011/0285836 A1 is arranged in such a manner that it emits photons at the iris and the retina of both eyes. An iris image sensor captures the image of the iris when the iris reflects the emitted light. A retina image sensor captures the image of the retina when the retina reflects the emitted light. A controller controls the iris and the retina illumination sources, whereby the captured iris and retinal images contain biometric data. The system for the biometric identification further comprises a housing with at least one user window on a first side, whereby the window is adapted to accommodate at least one eye of a user positioned on the first side of the housing. The housing also comprises at least one opposing window on the second side of the housing, where the opposing window is aligned with at least one user window, whereby this enables transmission of images between the object external to the housing and at least one user window as well as at least one opposing window. The device further comprises at least one illumination source in the housing emitting photons through the at least one user window to be reflected from at least one eye and the device also comprises at least one image sensor in the housing for capturing the image according to the photons reflected from at least one eye, the image having biometric data.

The disadvantage of this device is its relative complexity, even though it enables minituarization and automation. The complexity consists above all in the necessity to utilize different wavelengths of light for the iris and the retina sensing, which either requires using separate systems - an illumination source - a sensor for the retina and the iris sensing, or it requires consecutive switching between a pair of illumination sources and capturing both images (of both the iris and the retina) by one sensor, which in turn results in lower quality of sensing caused by the decrease in the number of images per second.

Medical applications of sensing the iris and the retina are dealt with in the patent documents 2008/018855 A1 , US 2012/150064 A1 , WO 0 199 027 A2 and others.

US 2008/018855 A1 proposes a solution for detecting aberrations of the human eye and automatic determination of a required correction by means of projecting special patterns onto the eye regions and their sensing by a digital sensor, e.g. by a CCD camera, followed by automatic evaluation. The system employs a relatively complex 3D structure by positioning a part of the optical system so as to obtain a high quality image. The system as such aims at the automation of the process of determining the required correction of the eye disorders in the field of dioptric correction, such as refraction, astigmatism, etc. US 2012/150064 A1 describes a method for carrying out procedures based on sensing biometric data from the human eye. Improvement of the acquired image resolution is accomplished by using parallel stochastic perturbative gradient descent (PSPGD) optimization with the purpose of reducing the costs and dimensions of the apparatus when compared to the existing known optical sensing systems.

WO 0 199 027 A2 discloses an identification apparatus with a remote data entry, which can be used for identification of individuals in emergency, when the identified person is not able to provide the required data. The system has the form of a portable device which consists of means of sensing biometric data from the human eye (the iris, the retina) and further consists of communications means of connecting to the base, from which on the basis of the sent captured biometric data of the person ^' s eye the system returns data about the person ^' s identity, health state, possibly also data necessary for the resuscitation of the person in question etc.

The aim of the invention is to eliminate or at least reduce the disadvantages of the background art.

Principle of the invention

The goal of the invention is achieved by an ophthalmic diagnostic apparatus, whose principle consists in that means of illumination are arranged in the tube of an illumination unit, in front of which an ocular is arranged, whereby arranged behind the tube of the illumination unit is an adaptive optical system, behind which a sensing unit is arranged, wherein the illumination unit, the adaptive optical system and the sensing unit are connected to the electronic unit, which is coupled with an expert system for diagnosing eye diseases and disorders and with the database of the patients ^' images.

The principle of this method of the ophthalmic diagnostic apparatus consists in that the process of obtaining the image of the retina and/or the iris of the patient ^' s eye and its evaluation as well as making a diagnosis takes place in the automatic mode in which after sensing the eye data are automatically pre-processed for image acquisition, subsequently the acquired images are used as input data for the connected expert system, by which the images are automatically evaluated, and which either makes a diagnosis of a possible eye disesase directly according to a connected database of eye diseases and disorders and/or provides the operator/doctor with a narrow range of possible eye diseases so that the operator/doctor can make a final decision.

The advantage of this solution is a completely independent process of sensing the retina and the iris of the patient ^' s eye by one apparatus and processing the acquired biometric data for diagnosing eye defects of the patient and also for automatic determination of the progression or degression of a condition previously detected in or on the eye of the patient. In traumatology, it is of particular advantage that this apparatus and its method of operation enable to carry out all the procedures even when the patient is in a coma, which is currently practically impossible because using the majority of ophthalmic apparatuses require cooperation from the patient, and therefore this apparatus significantly improves for example the diagnostics of possible cases of damage to the eye caused for instance by an accident, etc.

Description of drawings

The invention is schematically represented in the drawing, where Fig. 1 shows an overall diagram of the arrangement of the apparatus according to the invention, Fig. 2 is a flowchart of the decision logic of the apparatus and Fig. 3 represents the arrangement of the sensing system.

Specific description

The ophthalmic diagnostic apparatus, which is schematically represented in Fig. 1 , is used as follows: the patient puts his eye 6 directly on the eye-piece 1, which is connected to a tube with an illumination unit 2. This illumination unit 2 comprises LED illuminating elements emitting radiation in the IR spectrum and visible light, whereby the first part constitutes illumination 20 for acquiring the iris images and the second part constitutes the illumination 2Λ for acquiring the retinal images. The parts 20, 21 have a different construction within the illumination unit 2, because the illumination of the iris of the eye 6 is surface illumination, whereas the illumination of the retina of the eye 6 involves the illumination of the inner surface of the eye 6. The used radiation correctly accentuates important information in the retina and in the iris of the eye 6. The illumination 20 for obtaining the iris images is provided with a set of infrared diodes emitting light from the region near the infrared light (IR) up to the maximum wavelength of 1000 nm, typically for example the wavelengths of 780 nm, 870 nm, 940 nm, whereby this illumination 20 further comprises complementary diodes emitting visible white light, which serves to throw additional light on the eye 6 to influence the contraction/expansion of the pupil.

The illumination Λ_ for obtaining the retina images comprises a focusing source of infrared light IR with the wavelength of 780 nm, which serves to focus the adaptive optical system 3. The retina image acquisition itself then takes place by the visible white light radiation in order to obtain a colour image of the retina. Alternatively, it is possible for the purpose of capturing the retina image to use the light from the „blue-green" part of the spectrum, typically the light having the wavelength of approximately 500 nm ± 100 nm, as is the case of a scanning laser described further on.

The illumination 2J. for obtaining the retinal images includes a pair of crossed polarizing filters - the polarizing filter 210, which, in connection with the polarizing filter 30 of the adaptive optical system 3 situated before the sensing unit 4, enables to filter off the light reflected on the surface of/inside the eye 6.

The illumination 21 for obtaining the retinal images is in the advantageous embodiment in Fig. 3 is provided with a hollow circular aperture 220, i.e. an aperture with a gap shaped as an annular ring, which creates a light beam with a doughnut shaped aperture. The beams reflected from the retina then pass through the centre of this aperture, by which means it is ensured that the optical pathway of the illuminating beams is separated from the optical pathway of the beams reflected from the eye 6.

In an unillustrated example of embodiment the illumination unit 2 is equipped with means of creating the so-called optical accommodative point, i.e. a point visible by the patient, at which the patient ^' s eye 6 aims and focuses on it. Thus the optical axis of the patient eye 6 is aligned with the optical axis of the apparatus, which is important, for example, for the localization of the so-called blind spot on the retina of the eye 6, i.e. the point at which the optic nerve enters the eye 6 and through which the bloodstream flows into the retina. Here is the highest density of biometric information for identifying a person according to the retina. Due to the centering of the eye 6 (of the optical axis) it is possible to capture the image of the retina of the eye 6. Moreover, in this manner the eye 6 of every patient is always fixed approximately in the same position, which facilitates the subsequent pre-processing of the image by means of algorithms for identification and extraction of distinctive features of the retina and the iris of the eye 6 that is being sensed. Without focusing the eye 6 on the accommodative point, i.e. without the accommodation of the eye, it would be very difficult, if not even impossible, to capture the image of the retina of the eye 6.

The eye-piece 1 not only fixes the placing of the eye 6 in a position suitable for sensing, but at the same time also baffles the ambient light, and therefore the pupil of the eye 6, which is the part of the eye that regulates the amount of light entering the eye 6, does not contract and so it does not reduce the sensed area of the retina of the eye 6, because on a greater area sensed it is possible to identify a greater number of distinctive features for the diagnostics of the eye 6.

The tube with an illuminating unit 2 is connected to an adaptive optical system 3, which has an electrically controlled focus and aperture, and so it is possible to sense both the retina and the iris of the eye 6 by one optical system, whereby it is necessary to move the focus of the adaptive optical system 3 by the order of several millimeters and at the same time adapt the aperture so that the follow-up sensing unit 4 could cope with a different type of the sensed parts of the human eye 6.

Arranged behind the adaptive optical system 3 is a sensing unit 4, which comprises a CCD and/or a CMOS optical image sensor chip, which captures the image of the retina and the iris of the eye 6 by read-out.

In an unillustrated embodiment the sensing of the retina is carried out by a scanning method, in which the source of illumination is a semiconductor laser generating radiation of medium wavelengths (approximately 500 nm ± 100 nm). A light beam emitted from this laser is deflected in a horizontal and vertical direction by means of a pair of electrolytical deflecting mirrors and the reflection of this light beam from the retina is recorded on a photosensitive element, for example on a photodiode or phototransistor, to be further processed. If this scanning method is employed for obtaining the retinal image, it is necessary to complement the adaptive optical system 3 by a semi-transparent mirror, which reflects the radiation from the above-mentioned laser towards the retina of the eye 6 and, conversely, transmits the light reflected from the retina to the above-mentioned photosensitive element, i.e. detector. The retinal images can also be obtained for example by means of linear laser technology, when the retina is sensed after being illuminated by a linear laser. This enhances the accuracy of the sensing process.

The adaptive optical system 3 (that is focusing/optical zoom, shutter) is controlled either directly by the sensing unit 4, or by the connected electronic unit 7. which is equipped not only with means - both hardware and software- for obtaining image data from the sensing unit, but it is also equipped with means of controlling the adaptive optical system 3 and the illumination unit 2. The electronic unit 7 comprises a digital signal processor (DSP) or a microcontroller, or, possibly, an FPGA element, internal memory, communication interface, such as Ethernet, USB, means of wireless transmission and other necessary electronic components. The illumination unit 2, the adaptive optical system 3 and the sensing unit 4 are connected to the electronic unit 7, which controls their operation.

The electronic unit 7 comprises means of turning on and off the optical accommodative point, or means of changing its intensity or the colour of its light.

The electronic unit 7 further comprises means of turning on or off the illumination unit 2, or turning on and off selectively particular LED illuminating elements with respective wavelengths. The electronic unit 7 comprises means of changing the intensity of the radiation of the illumination unit 2 or also means of changing selectively the radiation of particular LED illuminating elements with respective wavelengths.

The electronic unit 7 further comprises means of changing the focusing/zoom and the aperture of the adaptive optical system 3.

The electronic unit 7 further comprises means of obtaining image data (samples) from the sensing unit 4.

The electronic unit 7 further comprises means of processing image data (of the retina and the iris of the eye) for extraction of distinctive features, which are subsequently used for automated ophthalmologic examination of the eye 6.

The electronic unit 7 further comprises means of extraction of distinctive features from the acquired samples for the purpose of automated ophthalmologic examination of the eye 6, whereby these means are composed particularly of software equipment and method of its operation, as will be described below.

The electronic unit 7 also comprises means of creating a biometric pattern according to appropriate standards (e.g. CBEFF), which can be either stored in the internal memory of the apparatus, which is protected, or can be sent outside of the apparatus itself by using a communications interface, such as Ethernet, USB, wireless transmission, etc.

The electronic unit 7 further comprises means of importing the biometric pattern from the environment outside the apparatus by means of a communication interface, e.g. Ethernet, USB, wireless transfer, etc.

The electronic unit 7 also comprises means of comparing extracted features of the current sample, i.e. the current biometric pattern, with the samples of the biometric pattern already recorded, or the previous biometric pattern either from protected internal memory, or from an external data storage device.

The electronic unit 7 further comprises means of issuing match or non-match decisions of the compared biometric patterns. This decision is afterwards passed to an external device through a communication interface, such as Ethernet, USB, wireless transmission, etc., or it is considered to be an automatic initial confirmation of the identity of the examined patient in order to avoid the results of different patients being confused and to obtain valid information regarding the state of the eye 6 that is examined in relation to the previous examinations, as will be described hereinafter.

In order to improve the operation of the optical system, an example of embodiment (not shown) includes a 3D adaptable stage, on which are arranged an eye-piece 1, a tube with a illumination unit 2, an adaptive optical system 3 and a sensing unit 4 and that enables the accurate positioning of these parts of the device in the optical axis of the eye 6 with the purpose of optimization of sensing. That means that this is an autonomous system for eye diagnostics 6, which improves the user ^' s comfort, the whole process of sensing and subsequent evaluation, including comparison of the results of the current examination with the previous results, being fully autonomous and automatic. The ophthalmic diagnostic apparatus according to the present invention can be complemented by other measurements used in ophthalmology, such as the measurement of intraocular pressure, etc.

The ophthalmic diagnostic apparatus according to the invention works in such a manner that the whole process of sensing is performed in the automatic mode, which does not require much of a cooperation on the part of the patient and at the same time the operator ^' s (doctor ^' s) role has been made significantly easier, since a number of individual steps which are otherwise carried out by the operator/doctor are automated, including making a diagnosis, making comparisons with the previous state, selecting a region of interest of the acquired image of the eye 6 for more specific diagnostics and automation of more detailed diagnostics, including automatic implementation of more specific diagnostics in the selected region of the image during the next medical examination and its comparison with the previous state, etc.

In the actual process of sensing the iris and retina by the apparatus according to Fig. 3 a person puts the eye on the area of the eye-piece 1 and fixes the eye on the accommodative point. The illumination 2 is turned off, the illumination 20 is on. The adjustable lens 8 and polarizing filter 30 are removed from the optic pathway. The sensing unit 4 captures the image of the eye 6 and the 3D adaptable stage automatically positions the optical axis of the device to the optical axis of the eye 6. IR LED illumination is used to provide light. Arranged in the optic pathway before the sensing unit 4 is IR filter 40, whose transparency band overlaps the spectral band of IR LED illumination 20. The intensity of IR LED and white LED illuminating elements in the illumination 20 is modified, which leads to the contraction of the pupil of the eye 6. The iris image is acquired. Subsequently the illumination 21_ with the active IR LED elements turns on and an adjustable lens 8 of the objective of the adaptive optical system 3 enters the optic pathway and automatic focusing on the retina of the eye 6 follows. After that the white LED elements of the illumination 21 are activated and the IR filter 40 is displaced from the optical path. The image of the retina is acquired.

The apparatus works in such a manner that after acquiring the images of the iris, the retina, or also intraocular pressure and, possibly, other parameters, automatic preprocessing of data is carried out so as to obtain the images. Afterwards the images thus acquired serve as entry data for the linked expert system, or, as the case may be, for a learning expert system, which automatically analyses the acquired images and either makes a diagnosis of a possible disease of the eye 6 directly, or provides the operator/doctor with a narrow range of possible diseases of the eye 6 so that the operator/doctor can make a decision. Medical records of each procedure of sensing can be safely stored for every patient in digital form and can be automatically as well as manually monitored. Also, comparisons can be made during a long period of time from the point of view of the detected disease and its treatment, which provides a very detailed comparison of the development of the disease both to the doctor and the patient, including the possibility to process automatically plausible differences between the images of one eye 6 of one patient in different periods of time by the connected expert system, and so it is possible to monitor very accurately a long-term development of the disease or, possibly, determine whether the treatment was successful. This parameter not only helps doctors, making their work easier, but can be also utilized for scientific research in ophthalmology.

The electronic unit 7 further comprises means of automatic or manual selection of a region of interest of the examined eye 6, e.g. means of a circular or oval or a different shaped selection of a limited area of the image. The term region of interest denotes for example the spot where a problem or a potential problem was detected during current examination or during any of the previous examinations, and so the apparatus focuses automatically on the spot and therefore can sense it for example with a higher degree of sensitivity, by which means it is possible to observe only the selected region of the eye with, for example, a pathological or potentially pathological finding, whereby the finding on a limited area of the acquired image is stored in the connected database of findings, which is, for instance, advantageous not only from the medical, but also from the technical point of view, since in contrast with storing the whole image, which takes up a lot of space, by storing only a selected part of the image it is possible to save the storage space of the device.

The electronic unit 7 comprises means of connection to the database of patients and means of connection to the expert system, which may be formed either by means of the electronic unit, or it may be formed by a separate electronic device, or by a combination of both. The expert system comprises a database of eye diseases and disorders and their distinctive features or it is connected to this database, wherein it is provided with means of comparing the acquired images of the eye 6 of the patient and may be also provided by means of comparing different images of the same eye 6 and their evaluation in cooperation with the expert system. The expert system is also equipped with means of extending autodiagnostic capabilities and ensuring more accurate results of autodiagnostics, such as the database update, working algorithm update, the learning system according to the decisions made by the operator/doctor about the correction of the results of the examination on the basis of recommendations or decisions of the expert system, etc.