System and method for an optoretinography eye measurement

Abstract

The invention relates to a system for an optoretinography eye measurement, comprising: a source of an input light beam (1), a light detector (2), preferably in form of a camera, an interferometer, comprising a reference arm (3) and an object arm (4), a first beam splitter (5), configured to receive the input light beam (1) from the source and to splitthe input light beam (1) into an object light beam (7) and a reference light beam (6) and further configured to direct the input light beam (1) to the object arm and the reference light beam (6) to the reference arm (3) respectively, wherein the object arm (4) is configured for guiding the object light beam (7) through the cornea of a subject's eye into the subject's eye and back to the light detector (2), wherein the reference arm (3) is configured for guiding the reference light beam (6) to a mirror (8) and back to the light detector (2), wherein said light detector (2) is configured and programmed for recording the object light beam (7) interfered with the reference light beam (6) for detecting diseases of the subject's eye. The system characterizes in that it further comprises a source of a stimulus light (9) and a second beam splitter (10) configured for projecting a stimulus light (9) onto the subject's eye through the second beam splitter (10), wherein the second beam splitter (10) is arranged within the path of the stimulus light (9) between the source of the stimulus light (9) and the patient's eye and is configured to receive the stimulus light (9) and to direct the stimulus light (9) onto the patient's eye and the stimulus light (9) is in a form of a pattern varying in space or varying in time. The invention also relates to a method for an optoretinography eye measurement.

Description

[0001] System and method for an optoretinography eye measurement

[0002] Technical Field

[0003] The present invention relates to optoretinography eye measurement, in particular to system for a flicker-optoretinography measurements, which raises safety concerns, specifically in the imaging techniques from the full-field family.

[0004] Background

[0005] Optoretinography is an in-vivo eye examination technique which objectively discriminates between responding and damaged photoreceptors in the retina. Typically, to acquire the data needed, a white-light or another visible light point source (usually a diode) is added as a stimulus to a standard device capable of imaging the retina which belongs to a group of OCT or scanning laser ophthalmoscope (SLO) systems. The added light source serves as an excitation pulse and the standard retina images are being taken before and after excitation so the photoreceptor size change in time can be extracted from the image sequence. The photoreceptor size change is interpreted as its healthy response to the stimulus.

[0006] Due to a sub-microscopic scale of image features needed to extract for proper optoretinography signal detection it is often desired to leave some areas of retina as a non-excited reference. Having an image with known reference areas which were not illuminated at all helps to differentiate the tiny dynamic signal from the noise in the illuminated areas. A general way of introducing such reference areas is based on scanning the illumination beam on a retina to form a pattern with mirrors attached to mechanical scanners. This requires a dedicated driving system and adds spacious, costly and complicated component to the existing eye imaging device.

[0007] Perimetry is a family of human eye measurement techniques aiming at mapping the retina and differentiating the areas which are responsive or non-responsive to light. This knowledge brings diagnostic potential against many degenerative diseases and ideally can be used periodically to monitor either the disease progression or treatment effects in time. Standard perimetry measurement methods used in medical and optometry practice suffer from a few difficulties - are either time-consuming themselves or require a lengthy preparation of the patient in a form of dark adaptation, or are even painful and causing huge discomfort. Any of these limitations brings either unacceptable measurement duration from the practice point of view (visits lasting around 30 minutes) or from the patient point of view, causing fatigue and strongly decreasing reliability of the measurement near the end of the procedure. As these techniques rely on the patient subjective response regarding their perception of the visibility of the light stimulus, they often lack repeatability and reliability. Other techniques, including electroretinography (ERG), can be painful and not applicable in some of the patient groups. All the currently used perimetry methods require a great dose of patient cooperation and thus exclude e.g. children or the elderly from the scope of this examination.

[0008] Document US9532708B2 discloses An electronically controlled fixation light system for ophthalmic systems. The ophthalmic system can include an ophthalmic imaging device that generates an image of a portion of an imaged eye, a fixation light controller that includes an input module, configured to receive an input in relation to the image generated by the ophthalmic imaging device, and a control signal generator that generates an electronic fixation light control signal in response to the received input, and a fixation light source, configured to receive the fixation light control signal, and to generate a fixation light according to the received fixation light control signal. A surgeon can image a portion of an eye with the imaging device, determine a misalignment of the imaged eye relative to the imaging device based on the image, and control the fixation light with an electronic control signal to reduce the determined misalignment.

[0009] Document US2015272438A1 discloses various embodiments for imaging retinal intrinsic optical signals (IOS) in vivo. According to various embodiments, imaging retinal intrinsic optical signals (IOS) may comprise illuminating a host retina with near infrared light (NIR) during a test period, wherein the host retina is continuously illuminated by the NIR light during the test period. Sequentially a host retina may be stimulated with a timed bursts of visible light during the test period. A series of images of the retina may be recorded with a line-scan CCD camera and the images may be processed to produce images of intrinsic optical signals (IOS) from retinal photoreceptor cells identified in the images. Document AU2021322335A1 discloses an OCT system for measuring a retina as part of an eye health monitoring and diagnosis system. The OCT system includes an OCT interferometer, where the interferometer comprises a light source or measurement beam and a scanner for moving the beam on the retina of a patient's eye, and a processor configured to execute instructions to cause the scanner to move the measurement beam on the retina in a scan pattern. The scan pattern is a continuous pattern that includes a plurality of lobes. The measurement beam may be caused to move on the retina by the motion of a mirror that intercepts and redirects the measurement beam. The mirror position may be altered by the application of a drive signal to one or more actuators that respond to the drive signal by rotating the mirror about an axis or axes.

[0010] None of the documents in the prior art discloses a solution in which the eye examination can be performed without any prior patient preparation or training, in a non-invasive setting and this way not limiting the technique use to highly collaborative patients only. What is more, thanks to the invention, there is a possibility to obtain the retina activity maps, effectively replacing the time- consuming or painful methods used currently in the medical practice.

[0011] Brief description of the invention

[0012] The essence of the invention is a system for an optoretinography eye measurement, comprising: a source of an input light beam, a light detector, preferably in form of a camera, an interferometer, comprising a reference arm and an object arm, a first beam splitter, configured to receive the input light beam from the source and to split the input light beam into an object light beam and a reference light beam and further configured to direct the input light beam to the object arm and the reference light beam to the reference arm respectively, wherein the object arm is configured for guiding the object light beam through the cornea of a subject's eye into the subject's eye and back to the light detector, wherein the reference arm is configured for guiding the reference light beam to a mirror and back to the light detector, wherein said light detector is configured and programmed for recording the object light beam interfered with the reference light beam for detecting diseases of the subject's eye.

[0013] The system characterizes in that it further comprises a source of a stimulus light and a second beam splitter configured for projecting a stimulus light onto the subject's eye through the second beam splitter, wherein:

[0014] - the second beam splitter is arranged within the path of the stimulus light between the source of the stimulus light and the patient's eye and is configured to receive the stimulus light and to direct the stimulus light onto the patient's eye and

[0015] - the stimulus light is in a form of a pattern varying in space and / or varying in time.

[0016] Preferably, the object arm is configured for guiding the object light beam through the cornea of a subject's eye into the subject's eye and back to the light detector through the first beam splitter.

[0017] Preferably, the reference arm is configured for guiding the reference light beam to a mirror and back to the light detector through the first beam splitter.

[0018] Preferably, the second beam splitter is located within the path of the input light beam, preferably between the first beam splitter and the subject's eye.

[0019] In an alternative preferred embodiment, the second beam splitter is located out of the path of the input light beam, preferably between the source of the stimulus light and the first beam splitter

[0020] Preferably, that the source of the stimulus light is a 2D display.

[0021] Preferably, the second beam splitter is a dichroic beam splitter.

[0022] Preferably, the stimulus light is in the form of a pattern differentiated in space.

[0023] Preferably, the pattern is in the form of a chessboard or circles or stripes or other arbitrary sets of pixels bright or dark.

[0024] Preferably, the stimulus light is in the form of a color stimulation. Preferably, the stimulus light is in the form of a visible light point source added as a temporal illumination pattern.

[0025] Preferably, the temporal illumination pattern are in the form of a periodic on-off temporal illumination patterns or an aperiodic on-off temporal illumination patterns.

[0026] Preferably, the temporal illumination pattern is rectangular or sinusoidal in time, potentially in aperiodic manner.

[0027] The invention relates also to the method for an optoretinography eye measurement using the system according to the invention. The method characterizes in that it comprises following steps: the input light beam is sent from the source of the input light beam, the input light beam reaches the first beam splitter, where it is split into the reference light beam and object light beam, wherein the input light beam is directed to the object arm and reaches the patient's eye, then after scanning the eye, it returns through the first beam splitter to the light detector, wherein the reference light beam is directed to the reference arm then it reflects from the interferometer, then it reflects from the first beam splitter so as to be directed straight at the light detector and reaches the light detector the stimulus light is sent from the display and reflects from the second beam splitter so as to deliver the stimulus into the patient's eye.

[0028] Brief Description of the Drawings

[0029] Preferred embodiment of the present invention are presented in a more detailed way with reference to the attached drawing, in which:

[0030] Figure 1 is a scheme of a system for an optoretinography eye measurement according to one preferred embodiment of the invention,

[0031] Figure 2 is a scheme of a system for an optoretinography eye measurement according to the other preferred embodiment of the invention,

[0032] Figure 3a-3d present the examples of patterns differentiated in space

[0033] Figure 4 presents the examples of patterns differentiated in time. Detailed Description

[0034] According to the preferred embodiment of the invention, a system for an optoretinography eye measurement is schematically shown in Fig. 1. The system comprises a source of an input light beam 1, a light detector 2, preferably in form of the camera, an interferometer, comprising a reference arm 3 and an object arm 4. The system comprises also a first beam splitter 5 that is configured to receive the input light beam 1 and to split the input light beam 1 into an object light beam 7 and a reference light beam 6 and further configured to direct the input light beam 1 to the object arm 4 and the reference light beam 6 to the reference arm 3 respectively.

[0035] The object arm 4 is configured for guiding the object light beam 7 through the cornea of a subject's eye into the subject's eye and back to the light detector 2.

[0036] The reference arm 3 is configured for guiding the reference light beam 6 to a mirror 8 and back to the light detector 2.

[0037] The light detector 2 is configured and programmed for recordingthe object light beam 7 interfered with the reference light beam 6 for detecting diseases of the subject's eye.

[0038] The system further comprises a source of a stimulus light 9 and a second beam splitter 10 configured for projecting a stimulus onto the subject's eye through the second beam splitter 10.

[0039] The source of the stimulus light 9 is preferably in form of a 2D display. Thanks to it, there is no need of adding any optical system to introduce the optoretinography stimulus. Such a display can be a fully functional video-grade color matrix capable of emitting strong white light from its entire area either at once or selectively with high resolution. In the optoretinography context this display may be a source of patterns in illumination but also an equivalent of a typically used LED light when a uniform illumination is required.

[0040] The second beam splitter 10 is arranged within the path of the stimulus light 9 between the source of the stimulus light 9 and the patient's eye and is configured to receive the stimulus light 9 and to direct the stimulus light 9 onto the patient's eye.

[0041] The stimulus light 9 is in a form of a pattern varying in space or varying in time. Preferably, the object arm 4 is configured for guiding the object light beam through the cornea of a subject's eye into subject's eye and back to the light detector 2 through the first beam splitter 5, which is shown in Fig. 1 and Fig. 2.

[0042] According to one preferred embodiment of the invention, the reference arm 3 is configured for guiding the reference light beam 6 to a mirror 8 and back to the light detector 2 through the first beam splitter 5.

[0043] According to one preferred embodiment of the invention, shown in details in Fig. 1, the second beam splitter 10 is located within the path of the input light beam 1, preferably between the first beam splitter 5 and the subject's eye.

[0044] The second beam splitter 10 can also be located out of the path of the input light beam 1, preferably between the source of the stimulus light 9 and the first beam splitter 5, which was shown in Fig. 2.

[0045] Preferably, the second beam splitter 10 is a dichroic beam splitter, i.e. one that reflects visible light (ORG) well and transmits infrared light (laser) well.

[0046] According to one preferred embodiment of the invention, the stimulus light 9 is in the form of a pattern differentiated in space. The stimulus light 9 serves as excitation pulse and the standard retina images are being taken before and after excitation so the photoreceptor size change in time can be extracted. The photoreceptor size change is interpreted as its healthy response to the stimulus. A display can be a fully functional video-grade color matrix capable of emitting strong white light from its entire area either at once or selectively with high resolution.

[0047] The pattern may be in the form of a chessboard (fig. 3a) or circles (Fig. 3b) or stripes (Fig. 3c) or sets of pixels bright or dark (Fig. 3d) or other arbitrary sets of pixels bright or dark. It is possible to mix these approaches in a single set.

[0048] This is to illustrate the principle only and other types of patterns are possible. Patterns can be also modified in time for various consecutive images taken to further enhance the signal-to-noise ratio using numerical approaches, e.g. with Hadamard patterns which form a complete base of pattern realizations. Signal to noise ratio is a measure that compares the level of a desired signal to the level of background noise. This optoretinography stimulus pattern generation system eliminates a need of arranging a mechanical scanning system and adding an extra optical system to steer the stimulus into the eye.

[0049] The stimulus light 9 may be in the form of a color stimulation as an extra possibility for more detailed examinations.

[0050] According to other preferred embodiment of the invention, the stimulus light 9 is in the form of a pattern differentiated in time. The stimulus light 9 is in the form of a visible light point source added as a temporal illumination pattern.

[0051] The invention also covers an option in which the stimulus light 9 is in the form of a pattern differentiated in space and differentiated in time.

[0052] Flicker optoretinography (f-ORG) is a dynamic version of ORG in which the stimulus is applied in an alternate manner, being switched on and off on a time-scale of human eye reaction speed, i.e. between 0 Hz and approximately a few tens of Hz (video rate). The actual temporal on-off pattern can be freely adjusted to enhance the response of specific eye properties and visualize them. A sequence of images is recorded as the stimulus is being modulated to track the behavior of the photoreceptors in a response to the illuminating light.

[0053] While in principle f-ORG can be applied to any existing retina imaging system capable of measuring the thickness of photoreceptor layers, due to a nanometer-scale feature replacement sought in the images and the temporal resolution needed to register the dynamic response of the retina, the most promising architecture is a STOC-T method.

[0054] It is possible to apply periodic on-off temporal illumination patterns or aperiodic ones. A special case of aperiodic flicker is a "chirped" pattern, called this way in an analogy to chirped laser pulses in which the optical field frequency varies in time. Here, in f-ORG, the stimulus on-off frequency would vary, for example linearly, from a few to a few tens of hertz in one measurement sequence. In particular, the temporal characteristic can be rectangular or sinusoidal in time, potentially in aperiodic manner (fig. 4). These are examples to illustrate the principle only and other types of temporal patterns are possible.

[0055] It is possible to use as the stimulus a light 9 source with engineered spectral properties, e.g. specifically targeting the response of selected group of photoreceptors only - red, green or blue. According to another preferred embodiment can be using an RGB LED which can have its color channels selectively powered to emit a specific combination of colors, corresponding to the diagnostic information needed.

[0056] Using a flicker optoretinography (f-ORG) method in a STOC-T eye imaging system makes it possible to obtain an objective and repeatable perimetry measurement in a time of the order of Is without any prior patient preparation or training, in a non-invasive setting and this way not limiting the technique use to highly collaborative patients only. The main advantage is a potential of performing repeated measurements for the same patient as frequently as it is needed which makes it practical to monitor the patient health in time and to arrange retinal function screening measurements across the society, not limiting the access to perimetry only to those patients needing it urgently and highly cooperative with the device operator.

[0057] The invention also relates to the method for an optoretinography eye measurement using the system according to the invention. In the first step, the input light beam 1 is sent from the source of the input light beam 1. Then, the input light beam 1 reaches the first beam splitter 5, where it is split into the reference light beam 6 and object light beam 7. The input light beam 1 is directed to the object arm 4 and reaches the second beam splitter 10, through which it runs and reaches the patient's eye, then after scanning the eye, it returns through the second beam splitter 10 and the first beam splitter 5 to the light detector 2. The reference light beam 6 is directed to the reference arm 3 then it reflects from the interferometer, then it reflects from the first beam splitter 5 so as to be directed straight at the light detector 2 and reaches the light detector 2. In the next step, the stimulus light 9 is sent from the display and reflects from the second beam splitter 10 so as to deliver the stimulus into the patient's eye.

[0058] According to yet another embodiment of the invention, the input light beam 1 and the stimulating light are delivered to the patient's eye at the same time.

Claims

Claims1. A system for an optoretinography eye measurement, comprising: a source of an input light beam (1), a light detector (2), preferably in form of a camera, an interferometer, comprising a reference arm (3) and an object arm (4), a first beam splitter (5), configured to receive the input light beam (1) from the source and to split the input light beam (1) into an object light beam (7) and a reference light beam (6) and further configured to direct the input light beam (1) to the object arm and the reference light beam (6) to the reference arm (3) respectively, wherein the object arm (4) is configured for guiding the object light beam (7) through the cornea of a subject's eye into the subject's eye and back to the light detector (2), wherein the reference arm (3) is configured for guiding the reference light beam (6) to a mirror (8) and back to the light detector (2), wherein said light detector (2) is configured and programmed for recordingthe object light beam (7) interfered with the reference light beam (6) for detecting diseases of the subject's eye, characterized in that the system further comprises a source of a stimulus light (9) and a second beam splitter (10) configured for projecting a stimulus light (9) onto the subject's eye through the second beam splitter (10), wherein:- the second beam splitter (10) is arranged within the path of the stimulus light (9) between the source of the stimulus light (9) and the patient's eye and is configured to receive the stimulus light (9) and to direct the stimulus light (9) onto the patient's eye and- the stimulus light (9) is in a form of a pattern varying in space and / or varying in time.

2. The system according to claim 1, characterized in that the object arm (4) is configured for guiding the object light beam (7) through the cornea of a subject's eye into the subject's eye and back to the light detector (2) through the first beam splitter (5).

3. The system according to claim 1 or 2, characterized in that the reference arm (3) is configured for guiding the reference light beam (6) to a mirror (8) and back to the light detector (2) through the first beam splitter (5).

4. The system according to claim 1 or 2 or 3, characterized in that the second beam splitter (10) is located within the path of the input light beam (1), preferably between the first beam splitter (5) and the subject's eye.

5. The system according to anyone of the claim 1-3, characterized in that the second beam splitter (10) is located out of the path of the input light beam (1), preferably between the source of the stimulus light (9) and the first beam splitter (5).

6. The system according to anyone of the claim 1-5, characterized in that the source of the stimulus light (9) is a 2D display.

7. The system according to anyone of the claim 1-6, characterized in that the second beam splitter (10) is a dichroic beam splitter.

8. The system according to anyone of the claim 1-7, characterized in that the stimulus light (9) is in the form of a pattern differentiated in space.

9. The system, according to claim 8, characterized in that the pattern is in the form of a chessboard or circles or stripes or other arbitrary sets of pixels bright or dark.

10. The system according to claim 8 or 9, characterized in that the stimulus light (9) is in the form of a color stimulation.

11. The system according to anyone of the claim 1-7, characterized in that the stimulus light (9) is in the form of a visible light point source added as a temporal illumination pattern.

12. The system according to claim 11, characterized in that the temporal illumination pattern are in the form of a periodic on-off temporal illumination patterns or an aperiodic on-off temporal illumination patterns.

13. The system according to claim 11 or 12, characterized in that the temporal illumination pattern is rectangular or sinusoidal in time, potentially in aperiodic manner.

14. A method for an optoretinography eye measurement using the system according to claims 1-13, characterized in that it comprises following steps: the input light beam (1) is sent from the source of the input light beam (1), the input light beam (1) reaches the first beam splitter (5), where it is split into the reference light beam (6) and object light beam (7),wherein the input light beam (1) is directed to the object arm (4) and reaches the patient's eye, then after scanning the eye, it returns through the first beam splitter (5) to the light detector (2), wherein the reference light beam (6) is directed to the reference arm (3) then it reflects from the interferometer, then it reflects from the first beam splitter (5) so as to be directed straight at the light detector (2) and reaches the light detector (2), the stimulus light (9) is sent from the display and reflects from the second beam splitter (10) so as to deliver the stimulus into the patient's eye.

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