Electrooculography

Abstract

An apparatus comprising means for determining that a user is reading text 52 on a display 14. The amount of light 16 entering at least one eye 17 of the user is controlled while the user is reading th

Description

TECHNOLOGICAL FIELD Examples of the disclosure relate to electrooculography (EOG). Some relate to EOG using a user head worn device. BACKGROUND EOG can be used to measure a standing potential between the front and back of an eye. Performing EOG measurements can require specialist equipment and be inconvenient and time consuming. It would be desirable to improve and / or enhance EOG. BRIEF SUMMARY According to various, but not necessarily all, examples there is provided an apparatus comprising means for: determining that a user is reading text on at least one display; controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor comprised in a user head worn device while the user is reading the text on the at least one display; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. In some examples, controlling an amount of light entering at least one eye of a user while the user is reading the text on the at least one display comprises at least one of the following: causing an amount of light output by at least one of the at least one display to change; or causing blocking of at least a portion of light from entering the at least one eye of the user. In some examples, the means are configured to determine at least one of the following: relative orientation information of the at least one display and the at least one user head worn device; or relative position information of the at least one display and the at least one user head worn device; and wherein the means are configured to determine the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information. In some examples, at least one of the following: determining relative orientation information comprises receiving at least one of the following: orientation information of the at least one display from at least one orientation sensor of the at least one display; or orientation information of at least one user head worn device from at least one orientation sensor of the at least one user head worn device; or determining relative position information comprises receiving distance information of a distance between the at least one display and the at least one user head worn device from at least one distance sensor. In some examples, the means are configured to cause display of text on the at least one display to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information. In some examples, performing at least one action comprises at least one of the following: causing change of at least one display characteristic of the at least one display; or causing output of at least one notification. In some examples, the at least one display characteristic of the at least one display comprises at least one of the following: brightness; contrast; color; magnification; font size; or font. In some examples, the at least one notification is configured to at least one of the following: notify the user that the at least one eye of the user is fatigued; notify the user of a deterioration in eye health of the at least one eye of the user. In some examples, the at least one user head worn device comprises an extended reality headset, and wherein the extended reality headset comprises the at least one display. In some examples, the at least one user head worn device comprises smart glasses, and wherein the at least one display is comprised in a device separate from the smart glasses. According to various, but not necessarily all, embodiments there is provided a method comprising: determining that a user is reading text on at least one display; controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor comprised in a user head worn device while the user is reading the text on the at least one display; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. In some examples, controlling an amount of light entering at least one eye of a user while the user is reading the text on the at least one display comprises at least one of the following: causing an amount of light output by at least one of the at least one display to change; or causing blocking of at least a portion of light from entering the at least one eye of the user. In some examples, the method comprises determining at least one of the following: relative orientation information of the at least one display and the at least one user head worn device; or relative position information of the at least one display and the at least one user head worn device; and the method comprises determining the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information. In some examples, at least one of the following: determining relative orientation information comprises receiving at least one of the following: orientation information of the at least one display from at least one orientation sensor of the at least one display; or orientation information of at least one user head worn device from at least one orientation sensor of the at least one user head worn device; or determining relative position information comprises receiving distance information of a distance between the at least one display and the at least one user head worn device from at least one distance sensor. In some examples, the method comprises causing display of text on the at least one display to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information. In some examples, performing at least one action comprises at least one of the following: causing change of at least one display characteristic of the at least one display; or causing output of at least one notification. In some examples, the at least one display characteristic of the at least one display comprises at least one of the following: brightness; contrast; color; magnification; font size; or font. In some examples, the at least one notification is configured to at least one of the following: notify the user that the at least one eye of the user is fatigued; notify the user of a deterioration in eye health of the at least one eye of the user. According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions for causing an apparatus to perform: determining that a user is reading text on at least one display); controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor comprised in a user head worn device while the user is reading the text on the at least one display; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. In some examples, controlling an amount of light entering at least one eye of a user while the user is reading the text on the at least one display comprises at least one of the following: causing an amount of light output by at least one of the at least one display to change; or causing blocking of at least a portion of light from entering the at least one eye of the user. In some examples, the computer program comprises instructions for causing an apparatus to perform determining at least one of the following: relative orientation information of the at least one display and the at least one user head worn device; or relative position information of the at least one display and the at least one user head worn device; and wherein the computer program comprises instructions for causing an apparatus to perform determining the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information. In some examples, at least one of the following: determining relative orientation information comprises receiving at least one of the following: orientation information of the at least one display from at least one orientation sensor of the at least one display; or orientation information of at least one user head worn device from at least one orientation sensor of the at least one user head worn device; or determining relative position information comprises receiving distance information of a distance between the at least one display and the at least one user head worn device from at least one distance sensor. In some examples, the computer program comprises instructions for causing an apparatus to perform causing display of text on the at least one display to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information. In some examples, performing at least one action comprises at least one of the following: causing change of at least one display characteristic of the at least one display; or causing output of at least one notification. In some examples, the at least one display characteristic of the at least one display comprises at least one of the following: brightness; contrast; color; magnification; font size; or font. According to various, but not necessarily all, embodiments there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform at least a part of one or more methods described herein. According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for performing at least part of one or more methods described herein. The description of a function and / or action should additionally be considered to also disclose any means suitable for performing that function and / or action. Functions and / or actions described herein can be performed in any suitable way using any suitable method. According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims. While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function BRIEF DESCRIPTION Some examples will now be described with reference to the accompanying drawings in which: FIG. 1 shows an example of the subject matter described herein; FIG. 2 shows another example of the subject matter described herein; FIG. 3 shows another example of the subject matter described herein; FIG. 4 shows another example of the subject matter described herein; FIG. 5 shows another example of the subject matter described herein; FIG. 6 shows another example of the subject matter described herein; FIG. 7A shows another example of the subject matter described herein; and FIG. 7B shows another example of the subject matter described herein. The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures. DETAILED DESCRIPTION Examples of the disclosure relate to at least one of the following: apparatuses, methods, or computer programs for and / or involved in EOG. Additionally, or alternatively, examples of the disclosure relate to at least one of the following: apparatuses, methods, or computer programs for and / or involved in performing EOG measurements while a user is reading. Additionally, or alternatively, examples of the disclosure relate to at least one of the following: apparatuses, methods, or computer programs for and / or involved in modifying at least one display characteristic of a display based, at least in part, on EOG measurements made while a user is reading. Additionally, or alternatively, examples of the disclosure relate to at least one of the following: apparatuses, methods, or computer programs for and / or involved in notifying a user of a deterioration in eye health based, at least in part, on EOG measurements made while a user is reading. In examples, EOG measurements can be obtained while a user is reading text on a display and at least one display characteristic changed based, at least in part, on the EOG measurements, and / or eye health of a user monitored based, at least in part, on the EOG measurements. The following description and drawings describe various examples of an apparatus comprising means for: determining that a user is reading text on at least one display; controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor comprised in a user head worn device while the user is reading the text on the at least one display; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. The means can comprise at least one processor; and at least one memory including computer program code; the at least one memory storing instructions that, when executed by the at least one processor, cause performance of at least part of at least one method described herein. As used herein, an apparatus and / or device and / or component for / comprising means for performing one or more actions should also be considered to disclose an apparatus and / or device and / or component configured to perform the one or more actions. Similarly, as used herein, an apparatus and / or device and / or component configured to perform one or more actions should also be considered to disclose an apparatus and / or device and / or component for / comprising means for performing the one or more actions. Description of performing an action should also be considered to disclose causing and / or controlling the action. For example, transmitting information should also be considered to disclose causing and / or controlling transmission of information. Similarly, description of causing and / or controlling an action should be considered to also disclose performing the action. FIG. 1 schematically illustrates an example of an apparatus 10. Various features referred to in relation to FIG. 1 can be found in the other FIGs. The apparatus 10 can be comprised / integrated in a device (see, for example, FIG. 2), for example in an electronic device. The apparatus 10 can be comprised in any suitable device. For example, the apparatus 10 can be comprised in a user device such as a smartphone, laptop, desktop, tablet, user head worn device and so on. For example, the apparatus 10 can be comprised in an extended reality headset, or smart glasses and so on. In examples, the apparatus 10 is configured to receive signals 12_R comprising information, for example data, such as signals 12_R from at least one sensor. The received signals 12_R / information in the received signals 12_R can originate from an entity outside of a device in which the apparatus 10 is comprised. Signals 12_R that originate from an entity outside of a device in which the apparatus 10 is comprised can be referred to as external signals. For example, the received signals 12_R / information in the received signals 12_R can originate from at least one sensor, such as at least one EOG sensor, and / or at least one orientation sensor, located in a device that is separate from a device in which the apparatus 10 is comprised. Additionally, or alternatively, the received signals 12_R / information in the received signals 12_R can originate from an entity that is also comprised in a device in which the apparatus 10 is comprised. Signals 12_R that originate from an entity comprised in a device in which the apparatus 10 is also comprised can be referred to as internal signals. For example, the received signals 12_R / information in the received signals 12_R can originate from at least one sensor, such as at least one EOG sensor, at least one orientation sensor, and / or at least one distance sensor located in a device in which the apparatus 10 is comprised. In examples, the received signals 12_R comprise at least one of orientation information or distance information. For example, the received signals 12_R can comprise orientation information of a display device, and / or orientation information of a user head worn device, and / or distance information of a distance between a user head worn device and a display device, and so on. In some examples, the apparatus 10 is configured to transmit signals 12_T comprising information, such as signals 12_T to control a component or device which can be referred to as control signals. The transmitted signals 12_T can be transmitted towards an entity outside of a device in which the apparatus 10 is located. Signals 12_T that are transmitted towards an entity outside of a device in which the apparatus 10 is located can be referred to as external signals. For example, the transmitted signals 12_T can be transmitted towards a device that is separate from a device in which the apparatus 10 is comprised. For example, the transmitted signals 12_T can be transmitted towards at least one sensor, such as at least one EOG sensor, and / or at least one display, located in a device that is separate from a device in which the apparatus 10 is comprised. Additionally, or alternatively, the transmitted signals 12_T can be transmitted towards an entity that is comprised in a device in which the apparatus 10 is comprised. Signals 12_T that are transmitted towards an entity comprised in a device in which the apparatus 10 is comprised can be referred to as internal signals. In examples, the transmitted signals 12_T comprise at least one control signal configured to control at least one of the following: at least one component or at least one device and so on. For example, the transmitted signals 12_T can comprise at least one control signal configured to control at least one display. The apparatus 10 can be a controller. See, for example, FIGs 7A and 7B. The apparatus 10 can be a device. In some examples, the apparatus 10 is configured to cause / control performance of at least part of at least one method described herein. In some examples, the apparatus 10 is configured to perform at least part of at least one method described herein. FIG. 2 schematically illustrates an example of a device 44. The device 44 can be an electronic device. The device 44 comprises at least one transceiver 46, at least one component 48, and an apparatus 10 as described in relation to FIG. 1. The device 44 can be any suitable device 44. In some but not necessarily all examples, the device 44 is a user head worn device, such as an extended reality headset and / or smart glasses. In some examples, the device 44 is a user device such as a smartphone or computer. The at least one transceiver 46 can be any suitable transceiver or transceivers 46. For example, the at least one transceiver 46 can comprise any suitable transceiver(s) for transmitting and / or receiving at least one signal 12. In examples, the at least one transceiver 46 is configured to transmit and / or receive one or more signals using wired and / or wireless communication. Any suitable wired and / or wireless communication protocol(s) can be used. In some examples, the at least one transceiver 46 can comprise one or more separate transmitters and receivers. In examples, the at least one transceiver 46 can be configured to receive at least one received signal 12_R as discussed in relation to FIG. 1. In examples, the apparatus 10 is configured to transmit one or more signals 12_T to the at least one transceiver 46 for transmission by the at least one transceiver 46. For example, the apparatus 10 can transmit at least one control signal to a device to control at least one display of the device. The at least one component 48 can comprise any suitable component or components of device 44. In examples, the at least one component 48 comprises at least one sensor 50, such as at least one user head worn EOG sensor, at least one orientation sensor, such as at least one inertial measurement unit (IMU), at least one distance sensor, such as at least one time of flight sensor, and so on. In some examples, the at least one component 48 comprises at least one display 14. In examples, the at least one transceiver 46 can be considered a component of the device 44. In examples, the apparatus 10 is configured to receive at least one signal 12_R from the at least one component 48. For example, the apparatus 10 can receive sensor information from at least one sensor 50. In examples, the apparatus 10 is configured to transmit at least one signal 12_T to the at least one component 48. For example, the apparatus 10 can transmit at least one control signal to at least one sensor 50, at least one display and so on. In some examples, the various components of the device 44 can be provided as at least part of a system distributed across multiple discrete devices. As illustrated in the example of FIG. 2, the at least one transceiver 46 and the at least one component 48 are operationally coupled to the apparatus 10 and any number of intervening elements can exist between them (including no intervening elements). Additionally, or alternatively, two or more elements of the device 44 illustrated in the example of FIG. 2A can be integrated or combined. Additionally, or alternatively, one or more elements of the device 44 illustrated in the example of FIG. 2 can be omitted. For example, the at least one transceiver 46 can be omitted. In examples, the device 44 is configured to perform at least part of at least one method described herein. FIG. 2 illustrates an example of an extended reality headset comprising an apparatus 10 as described herein, and at least one display 14. FIG. 2 illustrates an example of smart glasses configured to transmit signals to a display separate from the smart glasses. By way of example, reference is made to FIG. 4. FIG. 4 illustrates an example of a device 44. In the example of FIG. 4, the device 44 is a user head worn device 22 in the form of smart glasses. The smart glasses comprise a plurality of EOG sensors 20, which can be referred to as user head worn EOG sensors 20. The EOG sensors 20 are positioned to enable EOG information to be determined when a user is wearing the smart glasses. That is, the EOG sensors 20 are positioned in the smart glasses to be in contact with the user’s head in appropriate positions to enable EOG information to be determined when a user is wearing the smart glasses. In the example of FIG. 4, the smart glasses comprise 3 EOG sensors 20, one in each arm and one in the bridge, however any suitable number of EOG sensors 20 in any suitable locations can be used. In examples, the smart glasses can be configured as varifocals and can comprise a viewing area for long distances (top area, A), a viewing area for intermediate distances (middle area, B), and a viewing area for short distances (bottom area, C). In some examples, the smart glasses comprise an apparatus 10 as described in relation to FIG. 1. In some examples, the smart glasses are configured to transmit information to an apparatus 10 as described in relation to FIG. 1 located in a separate device. FIG. 3 illustrates and example of a method 300. One or more of the features discussed in relation to FIG. 3 can be found in one or more of the other drawings. Method 300 can be performed, for example, by at least one of an apparatus 10 of FIG. 1 or a device 44 of FIG. 2. In examples, method 300, and / or at least a part of method 300, can be a method of performing EOG. In examples, method 300, and / or at least a part of method 300, can be a method 300 of performing EOG measurements while a user is reading. In examples, method 300, and / or at least a part of method 300, can be a method 300 of modifying at least one display characteristic of a display based, at least in part, on EOG measurements made while a user is reading. In examples, method 300, and / or at least a part of method 300, can be a method 300 of notifying a user of a deterioration in eye health based, at least in part, on EOG measurements made while a user is reading. At block 302, method 300 comprises determining that a user is reading text on at least one display 14. In examples, block 302 comprises tracking eye movement of a user and determining that the user is reading text on a display based, at least in part, on the eye movement of a user. For example, the movement of at least one eye of a user can be tracked and it can be determined that the user is repeatedly moving the eye(s) generally between left and right looking positions indicating that the user is reading. Eye movement of the user can be tracked using any suitable method. In examples, the EOG sensors can be used to track eye movement of a user. Additionally, or alternatively, block 302 can comprise determining context information of a user and determining that a user is reading text on at least one display 14 based, at least in part, on the context information. Any suitable context information can be used. For example, information of at least one of location, movement, focus or display status can be used. In some examples, eye movement information of the user can be context information. For example, it can be determined that a user is sitting at home looking at a display that is displaying text, and based, at least in part, on this information it can be determined that the user is reading text on a display. At block 304, method 300 comprises controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display 14 to enable at least one EOG measurement to be determined. In examples, the amount of light entering at least one eye of the user is changed in coordination with the eye movement of the user while reading to enable at least one EOG measurement to be determined. The amount of light entering at least one eye of the user can be controlled in any suitable way. In examples, the amount of light entering at least one eye of the user can be controlled by at least one of the following: controlling an amount of light produced by at least one light source, or preventing at least some light from entering the at least one eye of the user. For example, the amount of light output by at least one of the at least one displays 14 can be changed to control the amount of light entering at least one eye of the user. For example, the luminance of the at least one display 14 on which the user is reading text can be changed to control the amount of light entering at least one eye of the user. Additionally, or alternatively, the amount of light produced by at least one ambient light source in the vicinity of the user can be controlled at block 304. For example, at least one control signal 12_R can be transmitted to control an amount of light produced by at least one smart bulb. In some examples, light reducing means, such as at least one shutter, light blocking mechanism, or controllable filter, is controlled to control the amount of light entering at least one eye of the user at block 304. In examples, a user head worn device 22 comprises light reducing means. Accordingly, in examples, controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display 14 comprises at least one of the following: causing an amount of light output by at least one of the at least one display 14 to change; or causing blocking of at least a portion of light from entering the at least one eye of the user. By way of example, reference is made to the example of FIG. 5. In the example of FIG. 5, a user is wearing a user head worn device 22 in the form of smart glasses. For the purposes of clarity, only the eyes 17 of the user are shown. The user is reading text 52 on a display 14 of a laptop that is separate from the smart glasses. In examples, the amount of light 16 produced by the display 14 of the laptop can be controlled in coordination with the movement of the eyes 17 of the user while the user is reading the text 52 to enable at least one EOG measurement to be determined. Additionally, or alternatively, light reducing means in the user head worn device 22 can be controlled to block at least a portion of light 16 from entering at least one eye 17 of the user in coordination with the movement of the eyes 17 of the user while the user is reading the text 52 to enable at least one EOG measurement to be determined. In examples, a controllable filter in each lens of the smart glasses is controlled to block at least a portion of the light 16 in coordination with the eye movement of the user while reading the text 16 to enable at least one EOG measurement to be made. Returning to the example of FIG. 3, at block 306, method 300 comprises receiving EOG information from at least one user head worn EOG sensor 20 comprised in a user head worn device 22 while the user is reading text on the at least one display. EOG information can comprise any suitable information to enable at least one EOG measurement to be determined. In examples, EOG information comprises voltages induced across the EOG sensors 20 in the user head worn device 22. See, for example, FIG. 4. Accordingly, in examples, light entering at least one eye 17 is controlled in coordination with the user eye movement while the user is reading text to determine EOG information while the at least one eye 17 of the user is in appropriate left and right positions caused by the user reading text. In this way, EOG information can be determined for a user while the user is reading and without having the user undergo a separate testing procedure to enable the EOG information to be obtained. In examples, the EOG information can be obtained passively and the user may not even be aware that the EOG information is being determined / received. At block 308, method 300 comprises determining, based, at least in part on the received EOG information, at least one EOG measurement. At least one EOG measurement can comprise any suitable EOG measurement or measurements. For example, at least one EOG measurement can comprise any suitable EOG measurement(s) to enable light adaptivity information of the at least one eye 17 of the user to be determined. For example, the at least one EOG measurement can comprise at least one of, light peak, dark trough, Arden ratio and so on. In examples, the at least one EOG measurement can be determined for at least one of fast oscillation and slow oscillation. In some examples, additional information can be determined and used at block 308 to determine at least one EOG measurement. Any suitable additional information can be used. For example, any suitable information can be used to improve accuracy of the at least one EOG measurement. In examples, method 300 comprises determining at least one of the following: relative orientation information of the at least one display 14 and the at least one user head worn device 22, or relative position information of the at least one display 14 and the at least one user head worn device 22, and the method 300 comprises determining the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information. Accordingly, in examples, at least one of the orientations or positions of the at least one display 14 and the user head worn device 22 relative to one another can be used in determining the at least one EOG measurement. For example, knowledge of the relative orientations and / or relative positions can be used to improve accuracy of the at least one EOG measurement. In some examples, determining relative orientation information comprises receiving at least one of the following: orientation information of the at least one display 14 from at least one orientation sensor of the at least one display 14, or orientation information of at least one user head worn device 22 from at least one orientation sensor of the at least one user head worn device 22. Any suitable orientation sensor or sensors can be used. For example, inertial measurement unit(s) (IMll(s)) can be used. In examples where, for example, an extended reality headset is used, a virtual orientation of a virtual display can be determined. In some examples, determining relative position information comprises receiving distance information of a distance between the at least one display 14 and the at least one user head worn device 22 from at least one distance sensor 32. Any suitable distance sensor or sensors 32 can be used. For example, at least one time of flight sensor / proximity sensor can be used. By way of example, reference is made to the example of FIG. 5. In the example of FIG. 5, orientation information of the user head worn device 22 and the display 14 can be determined based, at least in part, on information from orientation sensor(s) 28 in the device 22 and display 14. Similarly, in the example of FIG. 5, distance 30 between the user head worn device 22 can be determined based, at least in part, on information from distance sensor(s) in the user head worn device 22, for example. Returning to the example of FIG. 3, in examples where, for example, an extended reality headset is used, a virtual display distance can be determined. For example, a focus distance of the eye(s) 17 of the user can be determined. In examples, at least one of the relative orientation information or relative position information is used to determine the set distance or distance the eyes move horizontally while the user is reading text 52 on the at least one display 14. If at least one of the relative orientation information or relative position information changes, the updated information can be used to recalculate the distance the eyes move horizontally. For example, a user may change the relative orientation and / or position of the user head worn device 22 and at least one display 14 when using varifocal lenses. By way of example, reference is made to the examples of FIGs 4 and 5. As shown in the example of FIG. 4, varifocal lenses have different areas for viewing different distances (areas A, B, C). When using different areas, a user may change the orientation of the user’s head, and therefore user head worn device, and / or at least one display 14. Similarly, when using different areas, a user may change the distance 30 between the device 22, and the at least one display 14. For example, a user may be using the middle area, B, for a certain font size and set distance for EOG measurement(s) determined. However, the font size may become smaller and the user may, for example, move the display device away or tilt their head. The updated relative orientation and / or position can be determined and the set distance or distance the eyes 17 of the user move horizontally while reading the text 52 re-calculated. Returning to the example of FIG. 3, in some examples, method 300 comprises causing display of text 52 on the at least one display 14 to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information. Accordingly, in examples, the length of lines of text 52, or the average length of lines of text 52, on the at least one display 14, and therefore the horizontal distance that the user moves their eye(s) 17 while reading the text 52 for EOG measurement(s), can be controlled based, at least in part, on at least one of the relative orientation information or relative position information. At block 310, method 300 comprises determining based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye 17 of the user. Any suitable light adaptivity information can be determined. For example, any suitable light adaptivity information to enable a determination of at least one of eye health of the user or eye fatigue of the user can be determined. In examples, light adaptivity information comprises a light adaptivity profile of the at least one eye 17 of the user. The light adaptivity profile may comprise information relating to the eye’s ability to adapt to changes in brightness of light, and / or the speed which which the eye is able to perform this adaptation. At block 312, method 300 comprises performing at least one action based, at least in part, on the determined light adaptivity information. Consequently, FIG. 3 illustrates a method 300 comprising: determining that a user is reading text 52 on at least one display 14; controlling an amount of light 16 entering at least one eye 17 of the user while the user is reading the text 52 on the at least one display 14 to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor 20 comprised in a user head worn device 22 while the user is reading the text 52 on the at least one display 14; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye 17 of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. The at least one action can comprise any suitable action or actions. For example, the at least one action can comprise any suitable action or actions related to at least one of eye health, eye tiredness, eye fatigue and so on of the user. In examples, performing at least one action comprises at least one of the following: causing change of at least one display characteristic, or causing output of at least one notification. A display characteristic can be any suitable characteristic of a display. For example, a display characteristic can be any characteristic of a display that can be altered based, at least in part, on the determined light adaptivity information. In examples, a display characteristic can comprise at least one display setting. In examples a display characteristic can comprise at least one setting related to how at least one entity is displayed on the at least one display 14. In some examples, at least one display characteristic of the at least one display 14 comprises at least one of the following: brightness, contrast, color, magnification, font size, or font. For example, the brightness of the at least one display 14 can be changed based, at least in part, on the determined light adaptivity information to relieve eye tiredness and / or eye fatigue of a user and / or reduce or prevent eye further eye tiredness and / or eye fatigue of a user. The at least one notification can comprise any suitable information, and can have any suitable form or forms. For example, the at least one notification can comprise a visual component, an aural component, a haptic component and so on. The at least one notification can be output by any suitable device or devices. In examples, the at least one notification is configured to notify the user of any suitable information based, at least in part, on the determined light adaptivity information. In some examples, the at least one notification is configured to at least one of the following: notify the user that the at least one eye 17 of the user is fatigued, or notify the user of a deterioration in eye health of the at least one eye of the user. For example, a visual notification may be presented on the at least one display 14 notifying the user that the at least one eye 17 is fatigued, which can allow the user to take appropriate actions, such as rest, to avoid or mitigate eye health deterioration. For example, an aural notification may be presented to the user notifying the user that there has been a deterioration in eye health of the at least one eye 17, which can allow the user to seek appropriate medical help. Examples of the disclosure are advantageous and provide technical benefits. For example, examples of the disclosure enable EOG information to be acquired passively while a user is reading text on a display. This can allow, for example, for EOG information to be acquired in a way that is less intrusive to the user. Furthermore, this allows, for example, for results to be taken whenever a user is reading, which potentially can provide for results to be obtained multiple times a day rather than only when a user is willing to set aside time to perform a test to enable EOG information to be acquired. For example, examples of the disclosure enable a display to be tuned to specific response of a user’s eye(s). For example, examples of the disclosure enable at least one characteristic of a display to be changed based on light adaptivity information of a user determined while a user is reading text on a display. This can, for example, mitigate / reduce eye tiredness / fatigue of a user using the display. For example, examples of the disclosure enable passive monitoring of eye tiredness / fatigue and eye health of a user. Examples of the disclosure relate to a smart-glass system that uses electrooculography (EOG) and I MU sensors for performing passive testing to determine a profile for a user’s light adaptivity. This user profile can be used to tune display brightness settings and notify users about fatigue, tiredness, and ageing of the eyes. Examples of the disclosure comprises the following examples: Example 1: Electro-oculography (EOG) signals are used to measure the change in the standing potential of the eyeballs. Standing potential is recorded over time together with the display luminance and ambient illumination conditions. Example 2: IMU Sensors are used to measure the relative position of glass and devices. Such orientation information would be used during assessment of the user’s eyesight to improve the accuracy of the results when multifocal lenses (or correction for astigmatism) are used. Examples of the disclosure: • Notifies the user about fatigue, tiredness, ageing eyes • Passively adjust the luminance of the mobile device I laptop display. This would improve the reading experience of the user as the luminance adjustment would be personalized according to the response of the eye, in addition to adjustment known in the art and based on the measurement of the ambient illumination. Examples of the disclosure provide a smart sensing system for the glasses form factor. In examples, it comprises the following sensors. • 4 integrated electrodes for electro-oculography (EOG) placed at areas of naturally occurring contact with the user’s face • Outwards pointing proximity I time-of-flight (ToF) sensor in the bridge. • I MU sensors • It will have a supporting application running on laptop / phone recording the size of the text rendered on the display, brightness of the display and ambient illumination Examples of the disclosure provide a method where the standing potential is recorded over time together with the display luminance and ambient illumination conditions information. Measurements can be performed specifically when the user is reading a text rendered on a display. In this method, the length of the text line represents the set horizontal distance required for the EOG measurements and the mobile device I laptop screen luminance can be subtly altered to create required change in the luminance. Slow oscillation measurement would require the user to read text on the screen for about 12 minutes. In this case the measurement would be performed for example when the user activates a mobile device with a dark screen and starts reading longer texts. Fast oscillation measurement has more potential for mobile use cases, as in this method fast oscillation can be generated by alternating 60-75-s periods of dim and bright light content on the screen. Alternatively, the glasses the user is wearing may alter the illumination levels by dimming the electrically controlled shutter of the glasses. Based on the standing potential measurements, the trend in the time to achieve the EOG light peak (LP) in slow oscillation or light through (LT) in fast oscillation is determined. This can be used for tracking the changes in the ageing eyes and adjusting the user specific profile controlling the display brightness. This would improve the reading experience of the user as the luminance adjustment would be personalized according to the response of the eye, in addition to adjustment known in the art and based on the measurement of the ambient illumination. Another use cases would include notifying the user of fatigue, tiredness and ageing eyes. The length of the text line (that is, set distance) can be determined based on the position and orientation of the devices (for example, mobile device and glasses) with respect to each other, by using time-of-flight (ToF) and IMU Sensors. Such orientation information could be used during the assessment, for accurate definition of the set distance for the EOG measurement. Specifically, measurement results of the ToF and IMU sensors can be used to improve the accuracy of the results when multifocal lenses (or correction for astigmatism) are used. FIG. 4 explains the typical viewing areas of varifocal glasses. In the baseline case the user is viewing the content rendered on the mobile device screen through the area which is in between the viewing area for long distances (A) and the viewing area for intermediate distances (B). For a certain font size, viewing distance and optical power of the lenses this works well and the user is able to read the text comfortably. This sets the baseline for the set distance used in the EOG measurements. In examples, the font size changes smaller, and the user may use several strategies to improve the readability of the smaller text. For example, the user may move the device further away to be able to read the text better. Now the IMU in the mobile device and the ToF sensor in the glasses or in the device notice the movement, and based on the change in the system geometry, that is the change in the distance between the devices, the text line length (set distance, distance the eyes move horizontally) is re-calculated. Additionally, or alternatively the user may change the head orientation with respect to the device, for example lift their chin. Now the IM Us in the mobile device and the glasses, and the ToF sensor in the glasses or in the device can track the movement. The text line length (set distance, distance the eyes move horizontally) can be re-calculated based on the change in the system geometry and change in the optical power. FIG. 6 illustrates an example of a method 600. Fig 7A illustrates an example of a controller 730 suitable for use in an apparatus 10, such as apparatus 10 of FIG. 1 and / or FIG. 2. In examples, controller 730 can be an apparatus 10. Implementation of a controller 730 may be as controller circuitry. The controller 730 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). As illustrated in Fig 7A the controller 730 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 736 in a general-purpose or special-purpose processor 732 that may be stored on a computer readable storage medium (disk, memory etc.) to be executed by such a processor 732. The processor 732 is configured to read from and write to the memory 734. The processor 732 may also comprise an output interface via which data and / or commands are output by the processor 732 and an input interface via which data and / or commands are input to the processor 732. The memory 734 stores a computer program 736 comprising computer program instructions (computer program code) that controls the operation of the apparatus when loaded into the processor 732. The computer program instructions, of the computer program 736, provide the logic and routines that enables the apparatus to perform the methods illustrated in one or more of the accompanying Figs. The processor 732 by reading the memory 734 is able to load and execute the computer program 736. The apparatus comprises: at least one processor 732; and at least one memory 734 storing instructions that, when executed by the at least one processor 732, cause the apparatus at least to: determining that a user is reading text 52 on at least one display 14; controlling an amount of light 16 entering at least one eye 17 of the user while the user is reading the text 52 on the at least one display 14 to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor 20 comprised in a user head worn device 22 while the user is reading the text 52 on the at least one display 14; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye 17 of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. As illustrated in Fig 7A, the instructions, program, or code 736 may arrive at the apparatus 730 via any suitable delivery mechanism 762. The delivery mechanism 762 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD- ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 736. The delivery mechanism may be a signal configured to reliably transfer the computer program 736. The apparatus 730 may propagate or transmit the computer program 736 as a computer data signal. The term “non-transitory” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM). Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: determining that a user is reading text 52 on at least one display 14; controlling an amount of light 16 entering at least one eye 17 of the user while the user is reading the text 52 on the at least one display 14 to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor 20 comprised in a user head worn device 22 while the user is reading the text 52 on the at least one display 14; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye 17 of the user; and performing at least one action based, at least in part, on the determined light adaptivity information. The computer program instructions may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program. Although the memory 734 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage. In examples the memory 734 comprises a random-access memory 758 and a read only memory 760. In examples the computer program 736 can be stored in the read only memory 758. See, for example, Fig. 6B. Although the processor 732 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 732 may be a single core or multi-core processor. References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. As used in this application, the term ‘circuitry’ may refer to one or more or all the following: (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): i. a combination of analog and / or digital hardware circuit(s) with software / firmware and ii. any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory or memories that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device. The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the computer program 736. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted. Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described. In examples, an apparatus can comprise means for performing one or more methods, or at least part of one or more methods, as disclosed herein. In examples, an apparatus can be configured to perform one or more methods, or at least a part of one or more methods, as disclosed herein. The above-described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems 34 including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services. The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility. The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’ In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components. As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, 35 investigating, identifying, looking up (for example, looking up in a table, a database, or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also," determine / determining" can include resolving, selecting, choosing, establishing, and the like. In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements. Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims. Features described in the preceding description may be used in combinations other than the combinations explicitly described above. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus. Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result. In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure. Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim:

Claims

1. An apparatus (10) comprising means for:determining that a user is reading text (52) on at least one display (14);controlling an amount of light (16) entering at least one eye (17) of the user while the user is reading the text (52) on the at least one display (14) to enable at least one electrooculography, EOG, measurement to be determined;receiving EOG information from at least one user head worn EOG sensor (20) comprised in a user head worn device (22) while the user is reading the text (52) on the at least one display (14);determining, based, at least in part on the received EOG information, at least one EOG measurement;determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye (17) of the user; and performing at least one action based, at least in part, on the determined light adaptivity information.

2. An apparatus (10) as claimed in claim 1, wherein controlling an amount of light (16) entering at least one eye (17) of a user while the user is reading the text (52) on the at least one display (14) comprises at least one of the following:causing an amount of light (16) output by at least one of the at least one display (14) to change; orcausing blocking of at least a portion of light (16) from entering the at least one eye (17) of the user.

3. An apparatus (10) as claimed in claim 1 or claim 2, wherein the means are configured to determine at least one of the following:relative orientation information of the at least one display (14) and the at least one user head worn device (22); orrelative position information of the at least one display (14) and the at least one user head worn device (22); andwherein the means are configured to determine the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information.

4. An apparatus (10) as claimed in claim 3, wherein determining relative orientation information comprises receiving at least one of the following:orientation information of the at least one display (14) from at least one orientation sensor of the at least one display (14), ororientation information of at least one user head worn device (22) from at least one orientation sensor (28) of the at least one user head worn device (22); or determining relative position information comprises receiving distance information of a distance (30) between the at least one display (14) and the at least one user head worn device (22) from at least one distance sensor (32).

5. An apparatus (10) as claimed in claim 3 or 4, wherein the means are configured to cause display of text (52) on the at least one display (14) to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information.

6. An apparatus (10) as claimed in any preceding claim, wherein performing at least one action comprises at least one of the following:causing change of at least one display characteristic of the at least one display (14); orcausing output of at least one notification.

7. An apparatus (10) as claimed in claim 6, wherein the at least one display characteristic of the at least one display (14) comprises at least one of the following: brightness;contrast;color;magnification;font size; or font.

8. An apparatus (10) as claimed in claim 6 or 7, wherein the at least one notification is configured to at least one of the following:notify the user that the at least one eye (17) of the user is fatigued;notify the user of a deterioration in eye health of the at least one eye (17) of the user.

9. An apparatus (10) as claimed in any preceding claim, wherein the at least one user head worn device (22) comprises an extended reality headset, and wherein the extended reality headset comprises the at least one display (14).

10. An apparatus (10) as claimed in any of claims 1 to 8, wherein the at least one user head worn device (22) comprises smart glasses, and wherein the at least one display (14) is comprised in a device separate from the smart glasses.

11. A method (300) comprising:determining that a user is reading text (52) on at least one display (14);controlling an amount of light (16) entering at least one eye (17) of the user while the user is reading the text (52) on the at least one display (14) to enable at least one electrooculography, EOG, measurement to be determined;receiving EOG information from at least one user head worn EOG sensor (20) comprised in a user head worn device (22) while the user is reading the text (52) on the at least one display (14);determining, based, at least in part on the received EOG information, at least one EOG measurement;determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye (17) of the user; and performing at least one action based, at least in part, on the determined light adaptivity information.

12. A method (300) as claimed in claim 11, wherein controlling an amount of light (16) entering at least one eye (17) of a user while the user is reading the text (52) on the at least one display (14) comprises at least one of the following:causing an amount of light (16) output by at least one of the at least one display (14) to change; orcausing blocking of at least a portion of light (16) from entering the at least one eye (17) of the user.

13. A method (300) as claimed in claim 11 or claim 12, comprising determining at least one of the following:relative orientation information of the at least one display (14) and the at least one user head worn device (22); orrelative position information of the at least one display (14) and the at least one user head worn device (22); andthe method (300) comprising determining the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information.

14. A method (300) as claimed in claim 13, wherein at least one of the following: determining relative orientation information comprises receiving at least one of the following:orientation information of the at least one display (14) from at least one orientation sensor (28) of the at least one display (14); ororientation information of at least one user head worn device (22) from at least one orientation sensor (28) of the at least one user head worn device (22); or determining relative position information comprises receiving distance information of a distance (30) between the at least one display (14) and the at least one user head worn device (22) from at least one distance sensor (32).

15. A method (300) as claimed in claim 13 or 14, comprising causing display of text (52) on the at least one display (14) to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information.

16. A method (300) as claimed in any of claims 11 to 15, wherein performing at least one action comprises at least one of the following:causing change of at least one display characteristic of the at least one display; orcausing output of at least one notification.

17. A method (300) as claimed in claim 16, wherein the at least one display characteristic of the at least one display comprises at least one of the following:brightness;contrast;color;magnification;font size; or font.

18. A method (300) as claimed in claim 16 or 17, wherein the at least one notification is configured to at least one of the following:notify the user that the at least one eye of the user is fatigued;notify the user of a deterioration in eye health of the at least one eye of the user.

19. A computer program (736) comprising instructions for causing an apparatus (10) to perform:determining that a user is reading text (52) on at least one display (14);controlling an amount of light (16) entering at least one eye (17) of the user while the user is reading the text (52) on the at least one display (14) to enable at least one electrooculography, EOG, measurement to be determined;receiving EOG information from at least one user head worn EOG sensor (20) comprised in a user head worn device (22) while the user is reading the text (52) on the at least one display (14);determining, based, at least in part on the received EOG information, at least one EOG measurement;determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye (17) of the user; and performing at least one action based, at least in part, on the determined light adaptivity information.

20. A computer program (736) as claimed in claim 19, wherein controlling an amount of light (16) entering at least one eye (17) of a user while the user is reading the text (52) on the at least one display comprises at least one of the following: causing an amount of light (16) output by at least one of the at least one display (14) to change; orcausing blocking of at least a portion of light (16) from entering the at least one eye (17) of the user.

21. A computer program (736) as claimed in claim 19 or claim 20, wherein the computer program (736) comprises instructions for causing an apparatus (10) to perform determining at least one of the following:relative orientation information of the at least one display (14) and the at least one user head worn device (22); orrelative position information of the at least one display (14) and the at least one user head worn device (22); andwherein the computer program (736) comprises instructions for causing an apparatus (10) to perform determining the at least one EOG measurement based, at least in part, on at least one of the relative orientation information or the relative position information.

22. A computer program (736) as claimed in claim 21, wherein at least one of the following:determining relative orientation information comprises receiving at least one of the following:orientation information of the at least one display (14) from at least one orientation sensor (28) of the at least one display (14); ororientation information of at least one user head worn device (22) from at least one orientation sensor (28) of the at least one user head worn device (22); or determining relative position information comprises receiving distance information of a distance (30) between the at least one display (14) and the at least one user head worn device (22) from at least one distance sensor (32).

23. A computer program (736) as claimed in claim 21 or 22, wherein the computer program (736) comprises instructions for causing an apparatus (10) to perform causing display of text (52) on the at least one display (14) to be changed based, at least in part, on at least one of the determined relative orientation information or the determined relative position information.

24. A computer program (736) as claimed in any of claims 19 to 23, wherein performing at least one action comprises at least one of the following:causing change of at least one display characteristic of the at least one display (14); orcausing output of at least one notification.

25. A computer program (736) as claimed in claim 24, wherein the at least one display characteristic of the at least one display (14) comprises at least one of the following:brightness;contrast;color;magnification;font size; orfont.

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