Portable pupillometer

Abstract

A portable pupillometer comprising a light stimulus configured to illuminate at least the pupil of an eye to induce a pupillary reflex is provided. A camera is configured to capture a first pupillary baseline image and one or more second images when the pupillometer is directed at a subject's pupil, wherein the first pupillary baseline image is captured prior to pupillary reflex and the second images are captured following activation of the light stimulus. A processor is configured to process the first pupillary baseline image and the second images and determine: a pupillary reflex characteristic based on a difference between one of the second images and the first pupillary baseline image; and a pupil size based on the first pupillary baseline image. The processor activates a first indicator to provide a signal that correlates with pupil size, and a second indicator to provide a signal that correlates with the pupillary reflex characteristic.

Description

PORTABLE PUPILLOMETERFIELD OF INVENTION

[0001] The present disclosure relates to a portable pupillometer for measuring pupil size and reactivity.BACKGROUND OF THE INVENTION

[0002] The assessment of pupil characteristics is used by physicians, first responders and other caregivers to evaluate health characteristics in a subject. Pupil characteristics may provide an indication of conditions such as concussion, brain injury and stroke.

[0003] Traditionally, a manual penlight examination was used in which a clinician directed a beam of light toward the subject's eye and visually observed the pupil's response. This approach is inherently subjective, relying on the individual clinician's perception and judgement to estimate pupil characteristics. As a result, manual assessments suffer from significant variability, yielding results that are unreliable, inconsistent and difficult to reproduce. This presents a serious issue as changes in a subject’s pupil indicative of an acute condition may go undetected, risking the subject's health and possibly life.

[0004] Automated pupillometry devices have been developed in an effort to address the shortcomings of the manual penlight examination. However, existing automated pupillometers are designed for use in fixed clinical settings, such as hospital intensive care units and neurology departments. They are large, expensive devices which are not mobile, and therefore, cannot be used by caregivers operating in field environments, for example, at the scene of a road traffic accident or on a sports field.

[0005] Aspects of the disclosure seek to remedy these issues in the prior art.SUMMARY OF THE INVENTION

[0006] It is an object of the disclosure to provide an improved pupillometer for measuring pupil size and a pupillary reactivity or responsiveness characteristic.

[0007] According to an aspect of the present disclosure there is provided a portable pupillometer comprising a light stimulus configured to illuminate at least the pupil of an eye to induce a pupillary reflex. A camera is configured to capture at least a first pupillary baseline image and one or more second images when the pupillometer is directed at a subject’s pupil, wherein the first pupillary baseline image is captured prior to pupillary reflex and the second images are captured following activation of the light stimulus. A processor is configured to process the first pupillary baseline image and the second images and determine: a pupillary reflex characteristic based on a difference between one of the second images and the first pupillary baseline image; and a pupil size based on the first pupillary baseline image. The processor activates a first indicator to provide a signal that correlates with pupil size, and a second indicator to provide a signal that correlates with the pupillary reflex characteristic.

[0008] According to a further aspect of the disclosure, there is provided a portable pupillometer comprising; a camera configured to capture at least a first pupillary baseline image when the pupillometer is directed at a subject’s pupil; a processor configured to; process the first image and determine a pixel count of the iris in the first image and a pixel count of the pupil in the first image, calculate a scaling factor by comparing the pixel count of the iris in the first image and the pixel count of the pupil in the first image, and determine a pupil size by applying the scaling factor to an iris diameter constant to yield a diameter of the pupil. The processor activates a first indicator to provide a signal that correlates with the pupil size determined by the processor.

[0009] In some embodiments, the pupillometer further comprises a light stimulus configured to illuminate at least a portion of the pupil and the iris of an eye; wherein the camera is further configured to capture at least one second image following activation of the light stimulus; wherein the processor is configured to process the first pupillary baseline image and the at least one second image and provide a pupillary reflex characteristic based on a difference between the second image and the first pupillary baseline image; and the processor is configured to activate a second indicator to provide a signal that correlates with the pupillary reflex characteristic.

[0010] In some embodiments, the pupillary reflex characteristic comprises one or more of: the rate of change of pupil size; the absolute change in pupil size; and the percentage change in pupil size.

[0011] In some embodiments, the processor is configured to classify the pupillary reflex characteristic into one of three classification categories, and wherein the second indicator comprises three discrete indicators corresponding to the three classification categories. In some embodiments, the processor is configured apply a rule to the classification in a response to a determination that the pupillary reflex characteristic does not meet a predetermined criterion. In some embodiments, the rule comprises selecting whether the pupillary reflex characteristic is pupil size; the absolute change in pupil size; or the percentage change in pupil size.

[0012] In some embodiments, the camera is configured to spontaneously capture the first pupillary baseline image when the pupillometer is directed at a subject’s pupil. In other embodiments, the camera is configured to capture the first pupillary baseline image at a predetermined period or in response to a user input.

[0013] In some embodiments, the processor is configured to activate the light stimulus for a predetermined period forming a light exposure event, and the camera is configured to capture a plurality of second images during the light exposure event. In some embodiments, the predetermined period forming the light exposure event is between 500 and 2000 ms. In some embodiments, the first pupillary baseline image is captured within 150 ms of the beginning of the light exposure event. In some embodiments, the second image is captured at least 500 ms after the beginning of the light exposure event.

[0014] In some embodiments, the pupillometer further comprises an activation button in communication with the processor, wherein the processor is configured to activate the camera in response to a first press of the activation button. In some embodiments, the processor is configured to activate the light stimulus in response to a second press of the activation button.

[0015] In some embodiments, the pupillometer further comprises a mode switch configured to switch the working mode of the light stimulus between a flashlight mode and a pupillometer mode.

[0016] In some embodiments, the light stimulus comprises a plurality of lights arranged in a ring around the lens of the camera. In some embodiments, the first indicator comprises one or more lights to indicate pupil size. In some embodiments, the first indicator comprises a plurality of lights, each of which correspond with a pupil size, wherein the processor is configured to signal the light that corresponds to the determined pupil size. In some embodiments, the second indicator comprises one or more lights to indicate that the pupillary reflex characteristic is normal, abnormal or non-responsive.

[0017] In some embodiments, the second indicator comprises a green light, an amber light and a red light, and the processor is configured to activate the green light when the pupillary reflex characteristic is normal, the amber light when the pupillary reflex characteristic is abnormal and the red light when the pupillary reflex characteristic is non-responsive.

[0018] In some embodiments, the pupillometer is hand-held.

[0019] According to a further aspect of the disclosure, there is provided a method of measuring pupil size in a subject using the pupillometer of any one of the previous aspects of the disclosure.

[0020] According to a further aspect of the disclosure, there is provided a method of determining the pupil size of a subject comprising:- capturing a pupil size image comprising the subject’s pupil and iris;- processing the image to determine an iris pixel count and a pupil pixel count;- calculating a scaling factor by comparing the iris pixel count to the pupil pixel count; and- applying the scaling factor to an iris diameter constant to yield a diameter of the pupil.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] These and other features of the disclosure will become more apparent from the following description in which reference is made to the appended drawings wherein:FIGURE 1 shows a perspective view of a pupillometer in accordance with an embodiment of the present disclosure;FIGURE 2 shows a side view of the pupillometer of Figure 1;FIGURE 3 shows a front view of the pupillometer of Figure 1;FIGURE 4 shows a rear view of the pupillometer of Figure 1;FIGURE 5 shows a rear exploded view of the pupillometer of Figure 1;FIGURE 6 shows a front exploded view of the pupillometer of Figure 1;FIGURE 7 shows a schematic diagram of the connections of components of the pupillometer of Figure 1;FIGURE 8 shows an example diagram of a subject’s eye;FIGURE 9A shows an example sampling technique, using sixteen samples;FIGURE 9B shows an example sampling technique, using thirty -two samples;FIGURE 10 shows a method of determining pupil size using the pupillometer of Figure 1;FIGURE 11 A shows the pupillometer of Figure 1 at a first working distance from a subject’s eye;FIGURE 1 IB shows the pupillometer of Figure 1 at a second working distance from a subject’s eye;FIGURE 12 shows an example pupil size image comprising pixels (exaggerated for clarity) corresponding to the pupil, iris and sclera of the eye of Figure 8;FIGURE 13 shows a graph of pupillary response over time in response to a light stimulus of the pupillometer of Figure 1;FIGURE 14 shows method of determining a pupillary response using the pupillometer of Figure 1;FIGURE 15 shows a perspective view of a pupillometer in accordance with a further embodiment of the present disclosure;FIGURE 16 shows a front view of the pupillometer of Figure 15;FIGURE 17 shows a side view of the pupillometer of Figure 15; andFIGURE 18 shows an internal view of the pupillometer of Figure 15.DETAILED DESCRIPTION

[0022] The present disclosure relates to a portable pupillometer suitable for measuring the pupil size of a subject in both field environments, e.g. at the scene of an automobile accident, sports event or a remote mountain rescue scene, and clinical settings, such as hospitals or residential care facilities. The pupillometer is portable to allow first responders, physicians and other caregivers to take pupillary measurements and provide care in a wide range of settings and locations. The pupillometer may provide more certainty in the measurement of pupil size and pupillary response to a light stimulus, by reducing ambiguity associated with subjective manual penlight examinations.

[0023] Figures 1 to 6 illustrate a first embodiment of a pupillometer 100 in accordance with the present disclosure and Figures 15 to 18 illustrate a second embodiment of a pupillometer 400 in accordance with the present disclosure.

[0024] Figures 1 to 6 illustrate a pupillometer 100 in accordance with an embodiment of the present disclosure. The pupillometer 100 comprises a housing 120 carrying: a light stimulus 102 comprising a plurality of LEDs 104; an infrared camera 106; a processor 110; a first indicator 124 comprising nine LEDs (or pupil size indicating array), a second indicator 130comprising three “traffic light” LEDs (or “reactivity array” or “reactivity LEDs”), an activation button 140 and a mode switch 142.

[0025] The light stimulus 102 is configured to illuminate at least the pupil of a subject’s eye. In this embodiment, the light stimulus 102 comprises a plurality of light emitting diodes (LEDs) 104 (or “LED burst array”). In other embodiments, the light stimulus may comprise any suitable number or type of light source, projecting visible light in any suitable color to elicit a pupillary light reflex, also referred to herein as pupillary reflex or pupillary response. In this embodiment, the plurality of LEDs 104 comprises ten LEDs arranged in a ring or circle shape. It is envisaged that any suitable number or configuration of LEDs may be suitable to elicit a pupillary response (constriction of the pupil).

[0026] The camera 106 is configured to take images of at least a portion of the eye. The camera 106 in this embodiment is an infrared camera and may be any suitable infrared camera for use in a portable device. The infrared camera may be a camera configured for nearinfrared (NIR) imaging or for far infrared (FIR) imaging. For example, the camera sensor may include an OV2640 sensor for NIR imaging, or similar. The infrared camera 106 is configured to capture images of the subject’s eye, specifically images of the iris and pupil of the eye. The camera may be configured to spontaneously capture images, capture images at predetermined periods and / or capture images in response to a user input e.g. button press.

[0027] As illustrated in Figure 3, the lens 105 of camera 106 is located at the center of the ring of LEDs 104. The eye of the subject may reflect light from the light stimulus 102 into the lens 105 of the infrared camera 106, causing glare and other artifacts in the images taken by the camera 106. A ring of LEDs or other symmetrical configuration of light stimulus 102 may reduce the presence of unwanted glare and artifacts. In other embodiments, the light stimulus is located adjacent to the camera in a non-symmetrical manner.

[0028] The pupillometer 100 further comprises a focus target 108. In this embodiment, the focus target 108 comprises a red focus ring comprising a circular ring of high visibility plastic located within the ring of LEDs 104. The focus target 108 provides a focus point for conscious subjects to look at when their pupil size and, optionally, a pupillary reflexcharacteristic is being measured. By keeping the subject’s gaze on the focus target 108, the eye of the subject may be better aligned with the camera 106 of the pupillometer 100. The lens 105 of camera 106 is located at the center of the red focus ring of the focus target 108 such that the focus target 108 directs the subject to look directly into the lens 105 of the camera 106. It is understood that the color of the focus target 108 may be any suitable color and may also be in any suitable shape for alignment. In this regard, it is noted that the focus target 108 may be other than a ring, i.e. it may be adjacent to the lens 105, provided that is positioned such that the subject is generally looking into the camera lens 105.

[0029] The housing 120 is shaped substantially like a flashlight, with a first light-illuminating end 122 that is wider in circumference than the opposing second end which is distal thereto. Other shapes and designs are envisaged. In this way, the pupillometer 100 is configured to be hand-held and operated by one or both hands of the user, including a gloved hand of the user. In the embodiment of Figures 1 to 5, the total length of the device is around 170 mm, although this embodiment is non-limiting and other sizes are envisaged. The first illuminating end of the housing 122 includes the plurality of LEDs 104 of the light stimulus 102, camera 106 and focus target 108 are mounted. The first end 122 of the housing 120 is open to facilitate illumination and image capture of the subject’s eye while the housing provides protection to the LEDs 104, camera 106 and focus target 108 from external knocks and bumps, as illustrated in Figures 1 and 3. Thus, the first end 122 will generally comprise a shield that protects the light stimulus 102 and camera 106 but which does not impede their function. The first end may comprise a transparent (e.g. glass or plastic) cover.

[0030] The pupillometer 100 further comprises molded alignment sights 109 configured to assist in user alignment of the pupillometer 100 relative to the subject’s eye, as illustrated in Figure 3. In this embodiment, the camera 106 is an infrared camera configured to project wavelengths which are not visible to the human eye and so the molded alignment sights 109 may assist the user in aligning the camera 106 relative to the eye of the subject. In this embodiment, the alignment sights 109 are formed on the exterior of the housing 120 at the first end 122 of the housing 122 and comprise a pair of raised protrusions or bumps. The first end 122 of the housing 120 is circular and the pair of raised protrusions are diametricallyopposed on the circumferential surface of the first end 122, the protrusions extending radially outward. In this embodiment, the protrusions are located at the “top” and “bottom” of the first end 122 of the pupillometer 100 when held in a preferred alignment relative to the subject’s eye. In this way, the user may align the alignment sights 109 to the eyebrow and lower lash line of the subject, with the pupillometer held a working distance away from the subject’s face.

[0031] In use, the user, such as a physician, may hold the pupillometer 100 adjacent to the subject’s open eye, with the first end 122 of the housing 120 directed toward the eye. In some embodiments, the optimal working distance between the camera 106 and the subject’s eye is from 1 to 25 cm. In some embodiments, the optimal working distance between the camera 106 and the subject’s eye is from 5 to 25 cm. In other embodiments, the optimal working distance is between 5 and 18 cm. In other embodiments, the optimal working distance is between 8 and 15 cm.

[0032] In other embodiments, the alignment sights may comprise any other suitable marking or other indication to assist with alignment of the camera relative to the subject’s eye. In some embodiments, the alignment sights may additionally or alternatively comprise a spacer configured to span the distance between the first end of the housing and a portion of the subject’s body. For example, the spacer may comprise a plastic or metal elongate member with a first end configured to attach to the housing of the pupillometer and a second end configured to rest on the user’s cheek, for example. The spacer may be a single length or may be extendable and / or retractable to vary the length. The spacer may be fixed to the housing or may be removable. The spacer may help with alignment of the pupillometer and may also ensure the pupillometer is held within a constant, acceptable working distance from the subject’s eye.

[0033] The processor 110 (i.e. microcontroller or MCU) is configured to perform a plurality of tasks, including to process images captured by the camera 106, as will be described in further detail herein. In this embodiment, the processor 110 comprises a high-performance embedded controller built on the 32-bit ARM Cortex-M4 or N6 architecture (e.g.STM32F405 microcontroller). The microcontroller may be any micro compact, single-board computer integrating a processor core, memory and programmable input / output peripherals on one chip. The microcontroller may be configured for embedded systems, power electronics, control systems, and loT devices by executing specific, low-power tasks, and may comprise, for example, one of a: Arduino Mega 2560, Raspberry Pi Pico and STM32. The microcontroller may comprise a serial wire debug (SWD) interface, a grounding plate and any other suitable hardware for ease of electrical configuration and safety.

[0034] The first indicator 124 is configured to provide a signal that correlates with pupil size. In this embodiment, the first indicator 124 comprises a plurality of pupil size indicating LEDs 126 (also known as “pupil size indicators” or a “pupil size indicator array”). The pupil size indicating LEDs 126 comprise a white LED array. In this embodiment, the first indicator 124 comprises nine pupil size indicating LEDs 126 each corresponding to a size of pupil, namely “1 mm” to “9 mm” in 1 mm intervals. In the embodiment of Figures 1 to 6, the pupil size indicating LEDs 126 are located within the housing 120 and a plurality of windows formed in the housing 120 allow light from the corresponding pupil size indicating LED 126 to be visible to the user, thereby providing a visual signal.

[0035] The processor 110 is further configured to issue a signal to activate and / or deactivate one or more pupil size indicating LEDs 126 in response to a determination of pupil size performed by the processor 110. For example, if the processor 110 determines that the pupil size is “6 mm”, the processor may send a signal to the pupil size indicating LEDs 126 to activate the LED corresponding to “6 mm” and deactivate any other pupil size indicating LED 126 which was previously activated.

[0036] . Each pupil size indicating LED 126 is adjacent to a corresponding pupil size indicating marker 128 located on the externally facing surface of the housing to permit the user to read off the indicated pupil size based on the corresponding marker 128. In this example, the pupil size indicating markers 128 comprise the numbers “1” to “9”, increasing in intervals of one. For example, the “1” marker 128 is located next to the LED 126 for indicating the pupil size is “1 mm”, the “2” marker 128 is located next to the LED 126 forindicating the pupil size is “2 mm”, and so on. The pupil size indicating markers 128 may be printed, adhered, etched or manufactured on the exterior of the housing 120 in any suitable manner.

[0037] As an example, the processor 110 may determine the pupil size is 4 mm by processing an image taken by the camera 106. The processor 110 issues a signal to the first indicator 124 indicating the pupil size is 4 mm instructing the first indicator 124 to illuminate the pupil size indicating LED 126 corresponding to ”4mm”. The user may read from the marker 128 (i.e. the number “4”), next to the pupil size indicating LED 126 to confirm that the first indicator 124 is indicating a pupil size of “4 mm”.

[0038] In some embodiments, the processor 110 may be configured to issue a signal to illuminate all pupil size indicating LEDs 126 up to and including the corresponding size. In the above example, this would result in the four pupil size indicating LEDs 126 corresponding to “1 mm”, “2 mm”, “3 mm” and “4 mm” being illuminated. In other embodiments, only the pupil size indicating LED 126 corresponding to the pupil size measured is illuminated. It is also envisaged that colored light or flashing light may be used to indicate the measured pupil size in one or more pupil size indicating LEDs, e.g. four flashes corresponds to a pupil size of “4 mm”.

[0039] In other embodiments, the first indicator may comprise a strip of pupil size indicating LEDs and a marker comprising a linear scale from, for example, 1 to 9. In other embodiments, the first indicator may comprise a screen or display configured to display the pupil size. For example, the number “4” or the phrase “4 mm” may be displayed on the screen to indicate a pupil size of “4 mm”. In other embodiments, the first indicator may comprise a speaker configured to issue an audible indication. For example, the prerecorded word “four” may be issued from the speaker to indicate a pupil size of “4 mm”. It is appreciated that this list is non-exhaustive and other types of first indicator are envisaged.

[0040] The pupillometer 100 of Figures 1 to 6 may also comprise pupil size comparison markings 144 (or “pupil size discs”) comprising a plurality of disc-shaped markings located on an exterior of the housing 120, adjacent the plurality of pupil size indicating LEDs 126 (or“pupil size indicators” or a “pupil size indicator array”). In this embodiment, the pupil size comparison markings 144 comprise nine circles each having a corresponding diameter to the appropriate pupil size indicating LED 126 from 1 mm to 9 mm, increasing in 1 mm intervals. The user may compare the subject’s pupil size to the circles of the pupil size comparison markings 144 without requiring operation of the light stimulus 102 or the camera 106. In other words, pupil size may be approximated in an “offline” or “analogue” manner without requiring use of the light stimulus 102 or the camera 106, although user determination of pupil size may introduce subjectivity to the measurement. Such a feature may also aid the user in confirming the pupil size determination by comparing the indicated size with the corresponding comparison marking 144. This feature may additionally be useful to determine if there was an error in pupil size determination, either user error or pupillometer error that may indicate the pupillometer requires maintenance or repair. For example, an error would be evident if the pupillometer indicates that the pupil size is 2 mm but the user can see from a manual comparison with the pupil size comparison markings 144 that the true pupil size is at least 5 mm.

[0041] In this embodiment, the pupil size comparison markings 144 are textured and raised relative to the exterior surface of the housing 120, which may aid user grip e.g. using a gloved hand. The pupil size comparison markings 144 are also in a contrasting color to the color of the housing 120 which may aid visibility. In this embodiment, the markings are black to match the color of the pupil which may increase ease of comparison, however, the color of the markings is not limited to black.

[0042] In this embodiment, the pupil size indicating LEDs 126 are located directly between the pupil size comparison markings 144 and the pupil size indicating marker 128. In this way, the user may consult each pupil size indicating marker 128 when considering the illuminated pupil size indicating LED / s 126 and the associated pupil size comparison marking / s 144. In other embodiments, the associated pupil size comparison markings 144 may be located distal to the pupil size indicating LEDs 126 and may, optionally, comprise their own pupil size indicating markers 128.

[0043] The second indicator 130 is configured to provide a signal that correlates with a pupillary reflex characteristic. The second indicator 130 comprises three “traffic light” LEDs (also known as a “reactivity array” or “reactivity LEDs”) comprising a red light 134, amber light 136 and green light 138. It is appreciated that any suitable color / s of LED may be used, including ‘white’. The “traffic light” system is widely recognized, and in this context the colors are afforded the following meaning to each LED: red = unacceptable or “clinically absent”; amber = warning or “abnormal”; and green = acceptable or “normal”. For example, if the amber light 136 is activated, this may prompt the user to test the pupillary reaction again, or to err on the side of caution and assess the subject assuming a “worst case” scenario, i.e. as if the red light 134 was activated. In some embodiments, markings may be provided beside the three “traffic light” LEDs to indicate their color and / or meaning. An instruction manual may also be provided in this regard.

[0044] In other embodiments, the second indicator 130 may comprise a screen or display configured to display the indication of pupillary reflex characteristic. For example, the word “red” or “unacceptable” or a symbol of a “sad face” may be displayed on the screen to indicate the subject’s pupillary reflex falls outside a predetermined range of acceptable responses. Similarly, the word “green” or “normal” or a symbol of a “happy face” may be displayed on the screen to indicate the subject’s pupillary reflex falls inside a predetermined range of acceptable responses. The word “amber” or “abnormal” or “test again” may be displayed on the screen to indicate the subject’s pupillary reflex falls close to the lower end limit of the predetermined range of acceptable responses. In other embodiments, the second indicator may comprise a speaker configured to issue an audible indication or signal. It is appreciated that this list is non-exhaustive.

[0045] The processor 110 is configured to determine a pupillary reflex characteristic, as will be described in more detail herein. The processor 110 is configured to issue a signal to the second indicator 130 to activate one of the three “traffic light” LEDs (or “reactivity array”). For example, if the pupillary reflex characteristic is classified (or categorized) as “normal”, the processor 110 is configured to activate the green light 138, while the processor 110 isconfigured to activate the red light 134 when the pupillary reflex characteristic is classified as “clinically absent”, as will be described in more detail herein.

[0046] In some embodiments, the processor is configured to determine when the pupillometer 100 is within a predetermined working distance from the subject’s eye by measuring when an predetermined acceptable amount of the pupil is present in the image taken by the camera. In some embodiments, the predetermined acceptable amount is 25%, 50% or 100% of the pupil. The result of the determining may be indicated using a “red light blink / yellow light blink / green light blink” mechanism. This determination may occur prior to the light stimulus or light exposure event (i.e. before the plurality of LEDs 104 are illuminated).

[0047] Namely, the processor 110 may be configured to illuminate (flashing) the green light 138 of the second indicator 130 when the pupillometer 100 is aligned with the subject’s eye such that a predetermined acceptable amount of the pupil is visible. Subsequently, the processor 110 may determine the pupil size from the image and issue a command to the first indicator 124 to indicate the pupil size. The user will understand from the green light 138 blinking behavior activation and subsequent pupil size indication that the pupillometer 100 has successfully measured the baseline pupil size.

[0048] Similarly, the processor 110 may be configured to illuminate (flashing) the red light 134 of the second indicator 130 when the amount of the pupil visible falls outside the predetermined acceptable amount. The user will understand from the red light 134 blinking behavior activation that the device is misaligned and can take steps to better align the device, such as asking a conscious subject to look at the focus target 108 or by manually adjusting the distance and / or angle of the pupillometer 100 relative to the subject.

[0049] As shown in Figure 5, the pupillometer 100 comprises the activation button 140 which is configured to be pressed by the user. The pupillometer 100 further comprises a mode switch 142 (or “toggle switch”) configured to switch the working mode of the pupillometer 100 between a “pupillometer” mode and a “flashlight” mode. In this embodiment, the activation button 140 and toggle switch 142 are located at the second end 123 of the pupillometer 100 opposite, or distal to, the first end 122. However, as will be appreciated, theactivation button 140 and mode switch 142 may be located elsewhere on the pupillometer. The housing 120 is adapted to accommodate and permit access to the activation button and mode switch for use. The activation button 140 is coupled to the processor such that when a user presses the activation button 140, the processor 110 registers the input. In this way, the user can provide input to the pupillometer 100.

[0050] The pupillometer 100 further comprises a power source. In preferred embodiments, the power source comprises a rechargeable battery 114 and, optionally, a charging cable inlet 116 (e.g. a USB-C port). In some embodiments, the rechargeable battery may be removable for charging. It is envisaged that the power source may comprise a non-rechargeable battery and, in some embodiments, a lead connection to mains power. In the embodiment of Figures 1 to 6, the power source comprises a rechargeable lithium battery 114, charging cable inlet 116 (USB-C port) and charging indicator light 118 (also known as a “battery status LED” or “charging indicator”) to indicate characteristics of the battery, for example when the battery 114 is charging and / or the power level of the battery, e.g. whether it is sufficiently charged or requires charging.

[0051] Figure 6 illustrates internal components of the pupillometer 100 and Figure 7 illustrates a schematic diagram of the electrical connections between the components of the pupillometer 100. The power source is configured to power the camera 106, processor 110, first indicator 124, second indicator 130 and light stimulus 102. The activation button 140 and mode switch 142 independently allow the user to instruct or otherwise influence the mode and operation of the processor 106. Namely, the mode switch 142 is configured to place the pupillometer 100 in one of two modes, although in other embodiments the pupillometer 100 may have more modes. The activation button 140 allows the user to provide user-input as to when the light stimulus 102 is activated. Data may be transferred from the camera 106 to the processor 110, and the processor 110 is configured to issue command signals to the camera 106, first indicator 124, second indicator 130 and light stimulus 102. As illustrated in Figure 6, the components may be connected via wired connection. In some embodiments, one or more of the components may be wirelessly connected.

[0052] In both the “pupillometer” mode and “flashlight” mode, the pupillometer 100 may have an initial status of ‘asleep’, ‘power off or ‘standby’, e.g. due to a period of inactivity. A first press of the activation button 140 may switch on the device or send a signal to the processor 110 to initiate a status of ‘awake’ or ‘ready’. In the embodiment of Figures 1 to 6, the processor 110 is also configured to activate the camera 106 such that the camera begins capturing one image every 100 ms. The image data is sent from the camera 106 to the processor 110 and the processor 110 is configured to analyze whether an acceptable amount of the pupil is present in the image in real time. As described above, only when the image taken includes an acceptable amount of the pupil will the green light 138 blink. The user can use the “red light blink / green light blink” mechanism to correctly align the pupillometer 100 before proceeding.

[0053] A pupil size image (or “baseline image”) may be taken when an acceptable amount of the pupil and optionally, the iris, is present in the image. The processor 106 may be configured to determine pupil size of the subject from the pupil size image.

[0054] In the “flashlight” mode, a second press of the activation button 140 activates (i.e. turns on) the plurality of LEDs 104. A further press of the activation button 140 deactivates (i.e. turns off) the plurality of LEDs 104 and. In this way, the pupillometer functions as a flashlight and allows for a manual penlight examination to be performed.

[0055] In the “pupillometer” mode, a second press of the activation button 140 is configured to activate (i.e. turn on) the plurality of LEDs 104 for a predetermined period. In preferred embodiments, the predetermined period in which the plurality of LEDs 104 are activated is about 1500 ms (i.e. 1.5 s). In other embodiments, the predetermined period is between 500 and 2000 ms, although this range is non-limiting. There may be a latency period after initial light exposure before the pupil begins to constrict and remains constricted until the light stimulus is removed. The latency period may be from 50-200 ms. As such, to allow sufficient time for the latency period in addition for a sufficient pupillary response (constriction) to occur, the predetermined period is preferably greater than 500 ms to allow time for the pupil to constrict after the latency period has passed.

[0056] The second press of the activation button 140 may also cause the processor 110 to instruct the camera 106 to capture an image at each of a predetermined period that may be the same as or different from the image-capturing period before activation of the light stimulus 102. For example, the predetermined period may be every 50, 100 or 200 ms. For example, an image may be captured every 100 ms in a light stimulus event lasting 1500 ms to obtain 15 images. These examples are non-limiting and any suitable periods may be employed.

[0057] To determine a pupillary reflex characteristic, the camera 106 is configured to capture a first pupillary baseline image and a second maximally constricted image, and in some embodiments a series of second maximally constricted images. The first pupillary baseline image may be taken prior to illumination of the light stimulus 102 and may be the pupil size image (“baseline image”) used to determine pupil size. Such an image would be taken automatically by the camera 106 without the user being required to press the activation button 140 (outside of any initial button press to turn on or put the pupillometer 100 in a ready mode). The pupil size in the pupil size image provides a “baseline” or “ambient” pupil size reflective of the true size of the subject’s pupil. Certain illnesses, injuries and the consumption of narcotics and other substances may alter the pupil size, such that the baseline pupil size of the subject may indicate one or more health characteristics.

[0058] Alternatively, the first pupillary baseline image may be different to the pupil size image and may be taken by the camera 106 during the light stimulus event i.e. during the period that the light stimulus 102 is activated, as will be described in more detail herein.

[0059] Using data from the pupil size image, the processor 110 is configured to determine a pupil size of the subject’s pupil and activate at least one of the pupil size indicating LEDs 126 to indicate to the user the pupil size of the subject. Using data from the first pupillary baseline image and second maximally constricted images, and optionally one or more further images, the processor 110 is configured to determine a pupillary reflex characteristic and activate one of the three “traffic light” LEDs (or “reactivity array”) of the second indicator 130 to indicate pupil reactivity of the subject.

[0060] The user may then perform the above steps for the subject’s second eye such that a pupil size and pupillary reflex characteristic for each eye may be measured, in turn. In some embodiments, in the “pupillometer” mode, a third press of the activation button 140 places the pupillometer 100 in a standby mode, causing the processor 110 to deactivate the light stimulus 102. The camera 106 may remain activated such that the “red light / amber light / green light blink” mechanism for alignment is in operation. Any subsequent press of the activation button 140 may then activate (i.e. turn on) the plurality of LEDs 104 and cause the processor 110 to instruct the camera 106 to take a plurality of images over the course of the light stimulus event.

[0061] In some embodiments, the pupillometer will go into a “sleep” or “standby” mode after a predetermined period e.g. 30 seconds, when there has been no press of the activation button.. One or more of the first indicator 124 and second indicator 130 (e.g. red light, amber light and / or green light) may flash or provide a blinking warning that the pupillometer is about to enter the “sleep” or “standby” mode (e.g. at five seconds before the “sleep” or “standby” mode is due to begin). In this way, the pupillometer automatically resets and the first and second indicators are reset.Determining pupil size

[0062] Figures 8 to 12 illustrate an embodiment showing how the pupillometer 100 may determine the pupil size of the subject. In particular, Figure 10 illustrates a non-limiting example of the method steps that may be performed by the pupillometer to determine pupil size.

[0063] Figure 8 illustrates an example eye 146 of a subject. The eye 146 comprises a pupil 148 located within an iris 150, the iris surrounded by the sclera, wherein the pupil 148 has a pupil diameter dpand the iris has an iris diameter di. The pupil diameter dpis always smaller than the iris diameter di due to the anatomy of the eye 146. In persons over the age of 2 the diameter di varies very little between the population, namely the iris diameter di is typically around 12 mm (more specifically, around 11.8 mm with about 0.5 to 0.6 mm standard deviation). Further, during pupillary constriction and dilation, the size and shape of the irisremain unchanged. In this way, the iris diameter di provides a fixed reference to determine pupil size before and after pupillary reflex to the light stimulus 102. In this embodiment, images of the pupil and the iris may be taken using the camera 106.

[0064] The processor 110 is configured to determine a length characteristic of the iris 150 shown in the pupil size image taken by the camera 106. Preferably, the length characteristic is the image iris diameter, but in limited embodiments it may be the image iris radius, image iris area or the image iris circumference. The determining may be performed by any suitable image processing method, a non-limiting example of which is detailed herein.

[0065] Figure 10 illustrates a method 200 of determining a pupil size of a subject. The method 200 comprises capturing 202 an image of the iris 150 and pupil 148 (e.g. a pupil size image) of the subject’s eye 146 using the camera 106. The infrared camera may comprise a filter configured to convert the image to greyscale (i.e. non-color). Greyscale images may improve ease of pupil size determination by the processor 110 as categorization of pixel type (iris, pupil, sclera) may be simplified.

[0066] An example pupil size image is illustrated in Figure 12. The image is divided into a plurality of equal sized pixels 158. It’s envisaged that greater or fewer pixels may be used than is shown in Figure 12, and that the dimensions of the image may vary depending on the camera. The pixel size in Figure 12 is exaggerated for ease of comprehension. The image may also be cropped by the camera or processor to reduce computing power required during analysis. The processor 110 is configured to analyze, using color image processing, which pixels 158 contain the pupil 148 and / or which contain the iris 150. Alternatively or additionally, the processor 110 may be configured to determine which pixels 158 contain the sclera 152. Namely, the processor 110 may determine a color characteristic of each pixel 158. In a greyscale image, black pixels represent the pupil 148, white pixels represent the sclera 152 (or light glare / other unwanted artifacts) and various tones of grey pixel represent the iris 150.

[0067] Next, the processor calculates 204 the number of pixels 158 containing the iris 150. This may be performed by subtracting the number of pixels containing the pupil 148 andsclera 152 from the total number of pixels, or by counting the number of iris containing pixels. Any other suitable method may also be employed. The iris boundary 154 may then be determined by the processor 110, using data from the determination of the color characteristic of each pixel 158.

[0068] As illustrated in Figures 9A and 9B, the processor may sample the iris boundary 154 using radial lines. Figure 9A illustrates a “first pass” wherein 16 line samples are taken. It is appreciated that any suitable number of samples may be taken. The processor 110 may, optionally, assign a confidence value to each boundary. If confidence is low, a “second pass” may be performed wherein more line samples (e.g. 32 samples) are taken, as illustrated in Figure 9B.

[0069] The method 200 further comprises determining 206 the image iris diameter IDi. This measurement may be taken from the pupil size image as the diameter (in pixels) can be calculated from the iris boundary 154, as the size of each pixel is known. It is appreciated that various other techniques may be used to calculate the image iris diameter.

[0070] Next, the method 200 comprises determining 208 the scaling factor using true iris diameter approximation. Namely, approximating the true iris diameter IDT as 12 mm, a scaling factor can be calculated by the processor. The scaling factor may also be referred to as the “iris:pupil ratio” or a “correction factor”. For example, if the image iris diameter IDi is 8 mm and the true iris diameter IDT is 12 mm, the scaling factor is 1.5. Similarly, if the pixelated image iris diameter IDi is 15 mm and the true iris diameter IDT di is 12 mm, the scaling factor is 0.8. In other words, the dimensions taken from the pupil size image must be multiplied by the scaling factor to obtain the true measurements of the subject’s eye 146.

[0071] The method 200 further includes calculating 210 the number of pixels containing the pupil 148. The processor 110 may use the same image processing method as used for determining the image iris diameter IDi, or any other suitable image processing method, to obtain a length characteristic of the pupil 148 shown in the image. Preferably, the length characteristic is the image pupil diameter PDi, but in limited embodiments it may be the image pupil radius, image pupil area or the image pupil circumference. The pupil boundary156 may then be determined by the processor 110, using data from the determination of the color characteristic of each pixel 158.

[0072] The method 200 further comprises multiplying 214 the image pupil diameter PDi by the scaling factor to obtain the true pupil diameter PDT. The method 200 further comprises indicating 216 the true pupil diameter PDT to the user. As discussed above, the first indicator 124 is configured to indicate the true pupil diameter PDT.

[0073] The same scaling factor may be employed for measuring the true pupil diameter PDT on any one or more of the images captured by the infrared camera 106 during the same light exposure event (i.e. the period of exposure to the light stimulus 102). This is because the distance between the camera 106 and the eye 146 is substantially the same throughout the light exposure event. As such, the iris provides a fixed reference from which measurements of the pupil size can be taken across a plurality of images captured by the camera 106 using the same scaling factor. In some embodiments, the true iris diameter IDT is approximated at 11.8 mm. In other embodiments, the user may select a true iris diameter IDT from a predetermined list based on one or more of population data, age data, iris thickness, iris color and corrective factors. For example, if the subject is under 10 years of age, a smaller true iris diameter IDT may be used as an approximation.

[0074] The iris:pupil ratio scaling may mitigate error in measurements in relation to the distance the pupillometer 100 is held from the eye 146. For example, and as illustrated in Figures 11 A and 1 IB, the pupillometer 100 may be held at a first distance Li (e.g. 15 cm) from the subject’s eye during a “left eye test” and at a second distance L2 (e.g. 8 cm) from the subject’s eye during a “right eye test”.As L2, the scaling factor will be different for calculation of the pupil size in the “left eye test” compared to the “right eye test”. Both tests will result in a “true” or “absolute” pupil size, despite the difference in distance from the camera 106 to the eye.

[0075] In this way, an accurate pupil size measurement may be provided, so long as the pupillometer 100 is held within the broader working range. The iris:pupil ratio scaling mayalso mitigate error introduced by parallax when the device is held off-center from the central axis of the eye.

[0076] The above technique relies on the camera 106 being aligned with the eye 146 such that a predetermined acceptable amount of the iris 150 is present in the image taken by the camera. The processor 110 may be configured to reject or bypass images in which the iris boundary 154 is partially obstructed, out of focus, or distorted. The processor 110 may be configured to reject or bypass images in which image contrast is low, reflection is present, or the device angle is outside a predetermined tolerance. Alternatively or additionally, the processor 110 may be configured to reconstruct the obstructed or otherwise distorted portion of the image, such as by using known image reconstruction techniques. The processor 110 may correct for mild angular offset using ellipticity geometry of the iris 150. The iris boundary calculation may be averaged across several frames, which may improve accuracy of measurement.

[0077] The following is an example of pupil size determination in accordance with the method 200 of Figure 10. Taking an true iris diameter IDT (“iris constant”) of 11.8 mm, the image pupil diameter PDi (in pixels) can be divided by the image iris diameter IDi (in pixels), for example, 45 150 = 0.30. The pupil diameter is 30% the size of the iris diameter, this is the scaling factor (or “correction factor”). Multiply the scaling factor by the true (real) iris diameter IDT: 0.30 * 11.8 mm = 3.54 mm. The determination is that the true pupil diameter is 3.54 mm. In other words, the camera sees the pupil as 45 pixels wide and the iris as 150 pixels wide. Since the true iris diameter is assumed to be 11.8 mm, the true pupil diameter is 30% of that size.

[0078] In other embodiments, the pupil size may be determined using alternative methods. For example, as described above, a spacer spanning the distance between the first end of the housing and a portion of the subject’s body (e.g. cheek, forehead) may ensure the pupillometer is held a predetermined working distance from the eye. For example, the spacer may be 15 cm long. Due to the constant working distance, the image iris size and the iris: pupil scaling factor is fixed for every subject and every test. In this way, the processor 110 can determine the image pupil diameter PDi without calculating the image iris diameterIDi. The image pupil diameter PDi can be multiplied by the scaling factor to determine the true pupil diameter PDT.Determining pupillary reflex

[0079] The processor 110 may be further configured to determine a pupillary reflex characteristic of the subject using data from the first pupillary baseline image and the second maximally constricted image, or series of second maximally constricted images captured by the camera 106. It is understood that pupillary reflex is the response (constriction) of the pupil to a light stimulus.

[0080] With reference to the graph of Figure 13, a graph illustrating pupil diameter over time during the exposure period to the light stimulus 102 is shown. How the pupil size changes over time can be used to determine pupillary reflex characteristics. Figure 14 illustrates a non-limiting embodiment of a method 300 to determine pupillary reflex.

[0081] The method 300 comprises capturing 302 a first pupillary baseline image using the camera 106.

[0082] The method 300 further comprises receiving 304, at the processor 110, data from the camera 106 and determining the true pupil size PDT from the first pupillary baseline image, such as by using the abovementioned techniques.

[0083] The method 300 further comprises illuminating 305 the light stimulus. The processor 106 is configured to send a signal which activates the light stimulus 102 to initiate the light exposure event. In some embodiments, illuminating 305 the light stimulus occurs prior to capturing 302 the first pupillary baseline image, such that the first pupillary baseline image is taken during the light exposure event. For example, the first pupillary baseline image may be taken at timestamp 0 ms (i.e. immediately as the light stimulus is illuminated).

[0084] The method further comprises capturing 306 at least one second maximally constricted image using the camera 106.

[0085] As illustrated in Figure 13, the period of exposure to the light stimulus 102 begins at 0 seconds and lasts for a predetermined time such as 1500 ms. In this time, the camera 106 takes an image every 100 ms to yield fifteen images (shown by the vertical lines) over the period of exposure. As such, the method 200 may further include capturing a plurality of images during the illumination event (period of exposure to the light stimulus). Due to the anatomy of the eye, a latency period Piatency may exist, wherein there is a delay between the light stimulus 102 being activated and the eye registering the presence of light from the light stimulus 102. The pupil begins to constrict (the pupil diameter gets smaller) until a minimum pupil diameter is achieved. In the example of Figure 11, there is no change in pupil size in images 1 and 2 (during the latency period Piatency) and the pupil begins to constrict in the third image. At around the ninth image, a minimum pupil diameter is achieved and the pupil diameter remains at a minimum during images ten to fifteen.

[0086] The processor 110 may be configured to determine, from the fifteen images, when the pupil diameter reaches a minimum (i.e. is maximally constricted). This image (e.g. image nine) may be classified as the second maximally constricted image. The other images may be discarded. Alternatively, any other of the images showing a minimum pupil diameter (e.g. images ten to fifteen) may be selected, and the other images may be discarded. The first reflex image may be identical to the pupil size image, taken prior to the light exposure event.Alternatively, the first reflex image may be the first image taken by the camera during the light exposure event. In the example of Figure 11, the first image and second image taken by the camera illustrate a maximum pupil diameter so it may be equally suitable for the processor 110 to classify the first or second image as the first pupillary baseline image.

[0087] The method 300 further comprises receiving 308, at the processor 110, data from the camera 106 and determining the true pupil size PDT from the second maximally constricted image, such as by using the abovementioned techniques.

[0088] The method 300 further comprises comparing 310 the true pupil size PDT of the first pupillary baseline image and second maximally constricted image. The processor 110 is configured to receive data from the camera 106, as illustrated in Figure 7. The determinedfirst baseline pupil size and maximally constricted pupil size may be compared to obtain one or more pupillary reflex characteristics.

[0089] In some embodiments, the pupillary reflex characteristic is the absolute change in pupil size (as the pupil constricts under the light stimulus). This can be calculated by subtracting the baseline pupil size from the maximally constricted pupil size. For example, the baseline pupil size may be 5.0 mm and the maximally constricted pupil size may be 4.4 mm such that the absolute change in pupil size is -0.6 mm (or a 0.6 mm constriction).

[0090] In some embodiments, the pupillary reflex characteristic is a percentage change in pupil size. This can be calculated by taking the absolute change in pupil size (see above), dividing this value by the baseline pupil size, and multiplying by 100. For example, the baseline pupil size may be 5.0 mm and the maximally constricted pupil size may be 4.4 mm such that the absolute change in pupil size is -12% (or a 12% constriction).

[0091] In some embodiments, the pupillary reflex characteristic is the rate of change of pupil size (constriction velocity), namely how fast the pupil size changes over time. This can be calculated by dividing the absolute change in pupil size (see above) by the period of time between when the first pupillary baseline image and the second maximally constricted image were taken. For example, the baseline pupil size may be 5.0 mm and the maximally constricted pupil size may be 4.4 mm and the period between the first pupillary baseline image and a second pupillary reflex is 0.7 seconds such that the rate of change of pupil size (constriction velocity) is 0.86 mm / s.

[0092] Considering Figure 13, the average constriction velocity may be calculated as the change in pupil diameter divided by the time interval between the baseline pupil diameter and the minimum pupil diameter (aka maximally constricted pupil). For example, pupil constriction may begin after the second image, and the minimum pupil diameter may be reached around the ninth image. If the time interval between these two images is 800 ms and the change in pupil diameter is approximately 1.9 mm, the average constriction velocity is approximately 2.4 mm / s. As shown in Figure 13, constriction velocity is not constant over time. The highest constriction velocity occurs between images five and six, where the slope ofthe graph is steepest. The processor 106 may also be configured to calculate peak constriction velocity and other characteristics related to pupil constriction dynamics.

[0093] The method 300 further comprises categorizing or classifying 314 the pupillary reflex characteristic. For example, the pupillary reflex characteristic may be characterized by the processor 110 as “acceptable” or “normal”, wherein the green light 138 of the second indicator 130 is illuminated; “warning” or “abnormal / sluggish” wherein the amber light 136 of the second indicator 130 is illuminated; “clinically absent” or “non-reactive” wherein the red light 134 of the second indicator 130 is illuminated. The classification may be performed using predetermined “normal”, “abnormal” and “non-reactive” bounds for each pupillary reflex characteristic, as described below.

[0094] The method 300 further comprises indicating 316 the result of the classification using the second indicator 130, such as by the processor 110 issuing a signal to illuminate one of the red light 134, amber light 146 or green light 138.Classification for “standard” cases

[0095] If the determined pupil size in the first pupillary baseline image is less than 2.0 mm, the processor 110 may be configured to use both the absolute change in pupil size and the rate of change of pupil size (constriction velocity) as the pupillary reflex characteristics used to classify (or categorize) the pupillary reflex. In this case, the following “normal”, “abnormal” and “non-reactive” bounds for classification may be as follows:• “normal” - if i) absolute change in pupil size is 0.20 mm or more; AND ii) if the constriction velocity is 0.60 mm / s or more• “abnormal” - if absolute change in pupil size is 0.10-0.19 mm; OR if the constriction velocity is 0.30 to 0.59 mm / s; AND neither absolute change in pupil size nor constriction velocity are within the bounds of “non-reactive”• “clinically absent” or “non-reactive” - if absolute change in pupil size is 0.09 mm or less; OR constriction velocity is 0.29 mm / s or less

[0096] It is appreciated that these bounds are non-limiting examples only.

[0097] If the determined pupil size in the first pupillary baseline image is between 2.0 and 7.0 mm, the processor 110 may be configured to use both the percentage change in pupil size and the rate of change of pupil size (constriction velocity) as the pupillary reflex characteristics used to classify (or categorize) the pupillary reflex. In this case, the following “normal”, “abnormal” and “non-reactive” bounds for classification may be as follows:• “normal” - if percentage change in pupil size is 15% (constriction) or more; AND if the constriction velocity is 1.2 mm / s or more• “abnormal” - if i) percentage change in pupil size is between 7 and 14.9% (constriction); OR if the constriction velocity is between 0.6 and 1.19 mm / s; AND ii) neither percentage change in pupil size nor constriction velocity are within the bounds of “non-reactive”• “clinically absent” or “non-reactive” - if percentage change in pupil size is less than 7%; OR constriction velocity is less than 0.6 mm / s

[0098] It is appreciated that these bounds are non-limiting examples only.

[0099] If the determined pupil size in the first pupillary baseline image is 7.0 mm or more, the processor 110 may be configured to use the absolute change in pupil size as the pupillary reflex characteristic used to classify (or categorize) the pupillary reflex. In this case, the following “normal”, “abnormal” and “non-reactive” bounds for classification may be as follows:• “normal” - if absolute change in pupil size is 1.0 mm or more• “abnormal” - if absolute change in pupil size is 0.50-1.0 mm• “non-reactive” - if absolute change in pupil size is 0.49 mm or less

[0100] It is appreciated that these bounds are non-limiting examples only.Classification for “override”

[0101] Certain illnesses, injuries and the consumption of narcotics and other substances may alter the pupil size such that one pupillary reflex characteristic provides more accurate measurement or indication than another. To account for these edge-cases, the processor 110 may be configured to “override” the above “standard” classifications. In this way, the override may aid in determining the best pupillary reflex characteristic / s to use in classification of these edge-cases.

[0102] If the determined pupil size in the first pupillary baseline image is 1.0 mm or less (i.e. very small) and the percentage change in pupil size is under 10% constriction, the processor 110 may be configured to classify this result as “non-reactive” and consequently the red light 134 of the second indicator 130 is illuminated.

[0103] If the determined pupil size in the first pupillary baseline image is 2.0 mm or more AND the absolute change in pupil size is 2.0 mm or more, the processor 110 may be configured to classify this result as “normal” and consequently the green light 138 of the second indicator 130 is illuminated.Examples of “standard” and “override” classification

[0104] The following are non-limiting examples of “standard” and “override” (edgecase) classifications, using the example bounds outlined above:

[0105] Example 1:• Determined pupil size in the first pupillary baseline image: 4.8 mm• Determined pupil size in the second maximally constricted image: 3.8 mm• Absolute constriction: 1.0 mm• Percentage constriction: 20.8%• Constriction velocity: 1.35 mm / s• Classification: green or “normal” (percentage constriction at least 15% and constriction velocity at least 1.2)

[0106] Example 2:• Determined pupil size in the first pupillary baseline image: 5.0 mm• Determined pupil size in the second maximally constricted image: 4.4 mm• Absolute constriction: 0.6 mm• Percent constriction: 12.0%• Constriction velocity: 0.85 mm / s• Classification: yellow or “abnormal” (percentage constriction 7 to 14.9%, constriction velocity not red)

[0107] Example 3:• Determined pupil size in the first pupillary baseline image: 4.6 mm• Determined pupil size in the second maximally constricted image: 4.4 mm• Absolute constriction: 0.2 mm• Percent constriction: 4.3%• Constriction velocity: 0.22 mm / s• Classification: red or “non-responsive” (percentage constriction under 7% and constriction velocity under 0.60 mm / s)

[0108] Example 4:• Determined pupil size in the first pupillary baseline image: 1.8 mm• Determined pupil size in the second maximally constricted image: 1.5 mm• Absolute constriction: 0.30 mm• Percent constriction: 16.7%• Constriction velocity: 0.70 mm / s• Classification: green or “normal” (absolute constriction at least 0.20 and constriction velocity at least 0.6 mm / s)

[0109] Example 5:• Determined pupil size in the first pupillary baseline image: 1.7 mm• Determined pupil size in the second maximally constricted image: 1.55 mm• Absolute constriction: 0.15 mm• Percent constriction: 8.8%• Constriction velocity: 0.42 mm / s• Classification: yellow or “abnormal” (absolute constriction 0.10 to 0.19, constriction velocity not red)

[0110] Example 6:• Determined pupil size in the first pupillary baseline image: 1.6 mm• Determined pupil size in the second maximally constricted image: 1.54 mm• Absolute constriction: 0.06 mm• Percent constriction: 3.8%• Constriction velocity: 0.18 mm / s• Classification: red or “non-responsive” (absolute constriction under 0.10 and constriction velocity under 0.30)

[0111] Example 7:• Determined pupil size in the first pupillary baseline image: 7.8 mm• Determined pupil size in the second maximally constricted image: 6.6 mm• Absolute constriction: 1.2 mm• Percent constriction: 15.4%• Constriction velocity: 1.05 mm / s• Classification: green or “normal” (absolute constriction at least 1.0)

[0112] Example 8:• Determined pupil size in the first pupillary baseline image: 7.2 mm• Determined pupil size in the second maximally constricted image: 6.5 mm• Absolute constriction: 0.7 mm• Percent constriction: 9.7%• Constriction velocity: 0.55 mm / s• Classification: yellow or “abnormal” (absolute constriction 0.5 to 0.9, constriction velocity not red)

[0113] Example 9:• Determined pupil size in the first pupillary baseline image: 8.4 mm• Determined pupil size in the second pupillary reflex image: 8.1 mm• Absolute constriction: 0.3 mm• Percent constriction: 3.6%• Constriction velocity: 0.20 mm / s• Classification: red or “non-responsive” (absolute constriction under 0.5)

[0114] Example 10:• Determined pupil size in the first pupillary baseline image: 0.9 mm• Determined pupil size in the second maximally constricted image: 0.84 mm• Absolute constriction: 0.06 mm• Percent constriction: 6.7%• Constriction velocity: 0.12 mm / s• Classification: red or “non-responsive” (edge case: determined pupil size in the first pupillary baseline image is less than 1.0 mm and percentage constriction is less than 10%)

[0115] Example 11:• Determined pupil size in the first pupillary baseline image: 6.5 mm• Determined pupil size in the second maximally constricted image: 4.4 mm• Absolute constriction: 2.1 mm• Percent constriction: 32.3%• Constriction velocity: 1.10 mm / s• Classification: green or “normal” (edge case: absolute constriction at least 2.0 mm)

[0116] Example 12:• Determined pupil size in the first pupillary baseline image: 1.8 mm• Determined pupil size in the second maximally constricted image: 0.9 mm• Absolute constriction: 0.9 mm• Percent constriction: 50.0%• Constriction velocity: 0.95 mm / s• Classification: “normal” (Use “standard” classification and not “edge case” classification as absolute change in pupil size is 0.20 mm or more AND the constriction velocity is 0.60 mm / s or more)

[0117] In some embodiments, the processor comprises a memory configured to store one or more of: image / s captured by the infrared camera; data associated with an image / s captured by the infrared camera; raw measurement data; and the result of the determination of pupil size, iris size, classification and / or pupillary reflex or response. In some embodiments, the pupillometer comprises a data transmitter to transmit data stored on the memory. For example, the data transmitter may be configured to transmit data to a user’s smartphone, tablet or computer.

[0118] In some embodiments, the housing is further configured to carry a power button. In some embodiments, the brightness of the light stimulus, first indicator and / or second indicator may be adjustable. In this way, the pupillometer may be adjusted to match environmental light conditions e.g. inside a dark room, outdoors in sunlight.

[0119] In some embodiments, the housing of the pupillometer is configured to carry a clip, hook or means to attach a strap to the housing. In this way, the pupillometer may be attached to the user’s belt, pocket, harness or other item of clothing. The pupillometer may also be configured to be attached to a medical bag or the inside of an ambulance or other emergency vehicle, for example.

[0120] In some embodiments, the housing comprises plastic or aluminum. In this way, a lightweight housing and durable surface resistant to regular cleaning and disinfection may be provided. Preferably, the exterior surface of the housing 120 is substantially smooth to improve ease of disinfection. In some embodiments, the pupillometer is configured to be water resistant, in other embodiments the pupillometer is waterproof. In some embodiments, the pupillometer is configured to be resistant to extreme low and high temperatures.

[0121] Turning to Figures 15 to 18, a second embodiment of a portable pupillometer 400 is illustrated. In the following description, similar reference numerals will be used to indicate similar components in relation to the embodiment of Figures 1 to 6.

[0122] Figure 15 and 17 illustrate a pupillometer 400 comprising a housing 420 carrying: a light stimulus 402 comprising a plurality of LEDs 404; an infrared camera 406 with lens 405; a processor 410; a first indicator 424 comprising 10 LEDs (or pupil size indicating array), a second indicator 430 comprising three “traffic light” LEDs (or “reactivity array” or “reactivity LEDs”), and an activation button 440. No focus target (“red focus ring”), mode switch (“toggle switch”) or pupil size comparison markings (or “pupil size discs”) are present in this embodiment, although in other embodiments one or more of these features may be present.

[0123] As illustrated in Figure 15, the second indicator 430 differs from the first embodiment in that a red light 434, amber light 436 and green light 438 of the three “traffic light” LEDs are flush to the exterior of the housing 420, which is generally cylindrical is shape. The housing 420 is flashlight-shaped and the total length of the pupillometer 400 is around 170 mm, although other shapes and dimensions are envisaged. A first end 422 of the housing 420 permits light and infrared waves from the light stimulus 402 and infrared camera 406 to be directed toward the eye of a subject. The housing 420 carries the activation button 440, located on a second end 423 distal to the first end 422, as illustrated in Figure 17. The activation button 440 projects from the exterior of the housing 420. The housing 420 has a diameter of about 32 mm from the first end 422 for about 40 mm of length, tapers to about 27 mm over the next about 30 mm of length and is maintained at about 27 mm for the remaining 100 mm of length to the second end 423. These dimensions may be varied as will be appreciated.

[0124] The activation button 440 is coupled to the processor such that when a user presses the activation button 440, the processor 410 registers the input. In this way, the user can provide input to the pupillometer 400. A rechargeable battery 414, electrically coupled to a charging cable inlet, provides power to the pupillometer 400.

[0125] As illustrated in Figures 17 and 18, the housing 420 carries pupil size indicating LEDs 426 of the first indicator 424. In this embodiment, the pupil size indicating LEDs 426 comprise ten white LEDs each corresponding to a size of pupil, namely “1 mm” to “10 mm” in 1 mm intervals. The pupil size indicating LEDs 426 are positioned internally along the length of the housing 420 and a plurality of windows formed in the housing 420 allow light from the corresponding pupil size indicating LED 426 to be visible to the user, thereby providing a visual signal. The processor 410 is configured to illuminate a single one of these pupil size indicating LEDs 426 in response to a determination of pupil size.

[0126] Each pupil size indicating LED 426 is adjacent a corresponding pupil size indicating marker 428 to permit the user to read off the indicated pupil size based on the corresponding marker 428. In this example, the pupil size indicating markers 428 comprise the phrase “1 mm” sequentially up to “10 mm”, increasing in intervals of one. Each pupil size indicating marker 128 is located on the externally-facing surface of the housing, directly below a corresponding pupil size indicating LED 426, as illustrated in Figure 18. The pupil size indicating markers 428 may be printed, adhered, etched or manufactured on the exterior of the housing 420 in any suitable manner.

[0127] The function and features of the processor 410 are substantially identical to the function and features of the processor 110 in the pupillometer 100 of Figures 1 to 6. In this way, the pupillometer 200 is configured to determine pupil size and, optionally, a pupillary reflex characteristic using any of the aforementioned methods. The internal configuration of processor 100 illustrated in Figure 7 is substantially the same as the internal configuration of processor 400. It is understood that any suitable single feature or combination of features mentioned in relation to the pupillometer 100 of Figures 1 to 6 may be present in the pupillometer 400 of Figures 15 to 18.

[0128] One or more currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.

Claims

WHAT IS CLAIMED IS:

1. A portable pupillometer comprising;a light stimulus configured to illuminate at least the pupil of an eye to induce a pupillary reflex;a camera configured to capture at least a first pupillary baseline image and one or more second images when the pupillometer is directed at a subject’s pupil, wherein the first pupillary baseline image is captured prior to pupillary reflex and the second images are captured following activation of the light stimulus;a processor configured to process the first pupillary baseline image and the second images and determine:a pupillary reflex characteristic based on a difference between one of the second images and the first pupillary baseline image; anda pupil size based on the first pupillary baseline image;wherein the processor activates a first indicator to provide a signal that correlates with pupil size, andthe processor activates a second indicator to provide a signal that correlates with the pupillary reflex characteristic.

2. A portable pupillometer comprising;a camera configured to capture at least a first pupillary baseline image when the pupillometer is directed at a subject’s pupil;a processor configured to;process the first image and determine a pixel count of the iris in the first image and a pixel count of the pupil in the first image,calculate a scaling factor by comparing the pixel count of the iris in the first image and the pixel count of the pupil in the first image, anddetermine a pupil size by applying the scaling factor to an iris diameter constant to yield a diameter of the pupil;wherein the processor activates a first indicator to provide a signal that correlates with the pupil size determined by the processor.

3. The pupillometer of claim 2, comprising:a light stimulus configured to illuminate at least a portion of the pupil and the iris of an eye;wherein the camera is further configured to capture at least one second image following activation of the light stimulus;wherein the processor is configured to process the first pupillary baseline image and the at least one second image and provide a pupillary reflex characteristic based on a difference between the second image and the first pupillary baseline image; andthe processor is configured to activate a second indicator to provide a signal that correlates with the pupillary reflex characteristic.

4. The portable pupillometer of claim 1 or claim 3, wherein the pupillary reflex characteristic comprises one or more of the rate of change of pupil size; the absolute change in pupil size; and the percentage change in pupil size.

5. The pupillometer of claim 4, wherein the processor is configured to classify the pupillary reflex characteristic into one of three classification categories, and wherein the second indicator comprises three discrete indicators corresponding to the three classification categories.

6. The pupillometer of claim 5, the processor is configured apply a rule to the classification in a response to a determination that the pupillary reflex characteristic does not meet a predetermined criterion.

7. The pupillometer of claim 6, wherein the rule comprises selecting whether the pupillary reflex characteristic is pupil size; the absolute change in pupil size; or the percentage change in pupil size.

8. The pupillometer of any one of claims 1 to 7, wherein the camera is configured to spontaneously capture the first pupillary baseline image when the pupillometer is directed at a subject’s pupil.

8. The pupillometer of any one of claims 1 to 7, wherein the processor is configured to activate the light stimulus for a predetermined period forming a light exposure event, and the camera is configured to capture a plurality of second images during the light exposure event.

9. The pupillometer of claim 8, wherein the predetermined period forming the light exposure event is between 500 and 2000 ms.

10. The pupillometer of any one of claims 8 to 9, wherein the first pupillary baseline image is captured within 150 ms of the beginning of the light exposure event.

11. The pupillometer of any one of claims 8 to 10, wherein the second image is captured at least 500 ms after the beginning of the light exposure event.

12. The pupillometer of any one of claims 1 to 11, further comprising an activation button in communication with the processor, wherein the processor is configured to activate the camera in response to a first press of the activation button.

13. The pupillometer of claim 12, wherein the processor is configured to activate the light stimulus in response to a second press of the activation button.

14. The pupillometer of any one of claims 1 to 13, further comprising a mode switch configured to switch the working mode of the light stimulus between a flashlight mode and a pupillometer mode.

15. The pupillometer of any one of claims 1 to 14, wherein the light stimulus comprises a plurality of lights arranged in a ring around the lens of the camera.

16. The pupillometer of any one of claims 1 to 15, wherein the first indicator comprises one or more lights to indicate pupil size.

17. The pupillometer of claim 16, wherein the first indicator comprises a plurality of lights, each of which correspond with a pupil size, wherein the processor is configured to signal the light that corresponds to the determined pupil size.

18. The pupillometer of any one of claims 1 to 17, wherein the second indicator comprises one or more lights to indicate that the pupillary reflex characteristic is normal, abnormal or non-responsive.

19. The pupillometer of claim 18, wherein the second indicator comprises a green light, an amber light and a red light, and the processor is configured to activate the green light when the pupillary reflex characteristic is normal, the amber light when the pupillary reflex characteristic is abnormal and the red light when the pupillary reflex characteristic is non-responsive.

20. The pupillometer of any one of claims 1 to 19, wherein the pupillometer is hand-held.

21. A method of measuring pupil size in a subject using the pupillometer of any one of claims 1 to 20.

22. A method of determining the pupil size of a subject comprising:- capturing a pupil size image comprising the subject’s pupil and iris;- processing the image to determine an iris pixel count and a pupil pixel count;- calculating a scaling factor by comparing the iris pixel count to the pupil pixel count; and- applying the scaling factor to an iris diameter constant to yield a diameter of the pupil.

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