WO2015152818A1

WO2015152818A1 - Device to prevent a condition or disease associated with a lack of outdoor time

Info

Publication number: WO2015152818A1
Application number: PCT/SG2015/000089
Authority: WO
Inventors: Seang Mei Saw; Xinquan ZHANG; Suan Hui PU
Original assignee: National University Of Singapore; University Of Southampton
Priority date: 2014-03-31
Filing date: 2015-03-24
Publication date: 2015-10-08
Also published as: TWI695351B; TW201543424A; GB201405738D0

Abstract

The invention concerns a wearable device, including component parts thereof, that encourages individuals, especially children, to change their behavior by logging the amount of time a wearer spends outdoors with a view to encouraging the achievement of a daily target that has the effect of preventing myopia which is a condition or disease associated with a lack of time spent outdoors.

Description

Device to prevent a condition or disease associated with a lack of outdoor time Field of the Invention

The invention concerns a wearable device, including component parts thereof, that encourages individuals, especially children, to change their behavior by logging the amount of time a wearer spends outdoors with a view to encouraging the achievement of a daily target that has the effect of preventing myopia which is a condition or disease associated with a lack of time spent outdoors. Background of the Invention

Myopia is a significant globaf public health concern and there has been an increase in prevalence worldwide in recent decades. The number of people with this refractive error condition has been estimated as ranging between about 800 million to 2.3 billion worldwide. In Asia, there is an epidemic of myopia with much higher prevalence rates than in the rest of the world. For example, the prevalence of myopia in the United States in adults is reported to be 22.7%. However, the prevalence of myopia in Japan is reported to be (an overall prevalence of) 50%, in Taiwan it is reported to be 84% in people by 16 years of age, and in Hong Kong it is reported to be 36.7% in people from 5 to 16 years of age. Singapore has the highest myopia rates with 27.8% in 7 year old children and 83% in 18 years olds.

Myopia poses a great socio-economic burden (US$250 million per year in the United States), due to the loss of productivity from vision impairment as well as the cost of its correction. In Singapore, the mean annual direct cost of myopia for each Singaporean school child aged 7~9 years was estimated to be US$148.

Adults with significant myopia may have blinding ocular complications such as retinal tears and macular degeneration. Myopia is also associated with other vision- threatening ocular complications such as cataract and glaucoma.

Daytime outdoor activity is an essential risk factor for myopia Myopia is a complex multi-factorial trait driven by both genetic and environmental factors. Myopia generally develops during the early to middle childhood years, but it can also develop in the late teenage years or early adulthood. Notably, there are no known methods to prevent myopia in young children. Spectacles, contact lenses and atropine eye drops have not been proven, in randomized clinical trials, to prevent myopia.

Recent epidemiologic studies have found that more time spent outdoors could reduce the onset of myopia. In a study amongst 6-year old Chinese children, the myopia rate was 28% among Singaporean Chinese youth, while the prevalence in 6- year old Chinese children in Sydney, Australia was only 3.3%. The main difference hypothesized to be driving the disparity was the difference in time spent outdoors in the daytime between the two groups: estimated to be 3.0h per week in Singapore compared to 13.8h per week in Sydney. In a study amongst 1,765 six-year old children and 2,367 twelve-year old children from 2003 to 2005 in Sydney, it was found that more time spent outdoors, rather than sport per se, were associated with less myopia and a more hyperopic mean refraction [27]. The Orinda Longitudinal Study of Myopia, a cohort study of school-aged children seen annually during school grades 1 through 8, indicated that larger amounts of sports and outdoor activities decreased the odds of becoming myopic [28]. The Singapore Cohort Study on the Risk Factors for Myopia (SCORM) also found higher levels of outdoor activity were associated with lower prevalence of myopia [1]. Moreover, it has also been found that the progression of myopia is greater in winter than summer [29, 30]. In a school-based Guangzhou Outdoor Activity Longitudinal (GOAL) study on 1 ,789 children aged 6.6 years, the results indicated that children who had one hour of scheduled time outdoors, added to the school day, had a statistically significant reduction in refraction (0.86±0.77 D) compared to the intervention arm (0.75±0.69D, p<0.01) and axial elongation (0.61±0.35mm vs 0.59±0.33mm, p<0.05) after 2 years [14].

The main underlying factor for the association of time outdoors with myopia is outdoor light levels. Outdoor activities in the daytime provide very high ambient light which triggers the release of dopamine, a light-sensitive neuro-transmitter and ocular growth inhibitor that prevents myopia [31]. In a laboratory test, chick eyes exposed to laboratory light of 15,000 lux (Ix) for 5 hours per day or sunlight of 30,000 Ix for 15 minutes per day had significantly shorter eyes (8.81 +/- 0.05 mm; P < 0.01) and less myopic refractions (-1.1 +/- 0.45 D; P < 0.01), compared to chick eyes reared under normal laboratory illumination of 500 Ix [32]. Ambient light levels as high as 18,000 to 28,000 Ix could retard form-deprivation myopia in infant monkeys and there was an 87% reduction in the average degree of myopic anisometropia in the high-light reared monkeys [33]. Tree shrews exposed to elevated light levels (around 16,000 Ix for almost 8 hours) had reduced, by 44%, form-deprivation myopia (-3.6 ± 0.1 D vs. -6.4 ± 0.7 D) and reduced, by 39%, lens-induced myopia (-2.9 ± 0.4 D vs. -4.8 ± 0.3D) [34]. It has also been found that injection of the dopamine antagonist, Spiperone, is able to abolish the protective effect of high light intensity in chick eyes [35].

However, there is also another hypothesis that could explain the protective effect of outdoor activity. This hypothesis concerns the elimination of retinal image blur and peripheral hyperopic defocus [36]. During near work, the peripheral retina will experience a blur which would otherwise be absent during far viewing outdoors [37, 38]. The peripheral retina has a much larger surface than the fovea, believed to be responsible for controlling growth. Animal experiments have shown that peripheral vision can influence eye growth and refractive development, and distance viewing outdoors could slow ocular growth [39, 40]. A yet further hypothesis concerns the difference in spatial configuration outdoors and thus the way light impacts the eye, this difference in spatial configuration may have a protective effect on lens development.

Yet one further hypothesis concerns the amount of excessive blue-green wavelength in outdoor scenes which may also be protective against myopia [41]. In the average sunlit outdoor scene, there is a preponderance of blue light with some green light and a markedly decreased amount of red light [41]. Young chick eyes that were reared under excessive red light developed myopia when compared to chick eyes reared under excessive blue or white light [42]. Additions of blue light of more than 2 hours per day to 10 hours of red light induced hyperopia. Moreover, a study on red- green color vision deficiency in a group of school students found that the prevalence of myopia was significantly lower than a control group [43].

It follows that if myopia is to be prevented a higher exposure to the beneficial effects of outdoor conditions is to be encouraged. To this end, we have devised a novel portable device that tracks the amount of time spent outdoors, typically daily and provides a daily target that is to be achieved by the wearer, thus changing the behavior of the wearer. More specifically, the device is adapted to measure a wearer's exposure to ambient light illuminance over the course of each day and to determine the amount of time a user is exposed to lux levels greater than a threshold value set to distinguish typical outdoor illuminance over typical indoor illuminance [16]. Thus we have developed a motivational device that aims to change health behavior and enable parents to effectively and conveniently, encourage children to engage in more outdoor activities to prevent myopia. It is expected that the device will also be helpful in clinical trials of outdoor programs.

Statements of the Invention

According to a first aspect of the invention there is provided a wearable device to prevent myopia by motivating and increasing the amount of time a wearer spends outdoors during the day, comprising: .

a) at least one light sensor adapted to measure light;

b) at least one display device;

c) at least one Real Time-Clock (RTC);

d) at least one power source;

e) a non-volatile memory;

f) a microcontroller or microprocessor; and

g) embedded software residing in the microcontroller and/or the non-volatile memory;

wherein said embedded software is set, or can be set, to define a light threshold value whereby light measured by said light sensor exceeding said threshold is recorded in said memory for the amount of time said light persists and further wherein said embedded software is set, or can be set, so that within any specified time interval the cumulative amount of time that light exceeds said threshold is recorded in said memory and displayed on said display device. In a first preferred embodiment of the invention said time interval is a day or 24 hours, although larger periods may be also used to work the invention such as two or more days, including three, four, five or six days, or even a week or 7 days.

In yet a further preferred embodiment of the invention said embedded software is set, or can be set, such that a target value is defined for said cumulative amount of time that light having a unit of measurement, such as illuminance, greater than said threshold is experienced. Moreover this target value is ideally displayed on said display device and the amount of time remaining in said time interval to achieve this target value is also displayed on said display device. Typically, the target value is between 2 and 4 hours, including all 1 minute intervals there between, per day. Most typically, though not exclusively, said target value is 3 hours or approximately 3 hours.

In a further preferred embodiment of the invention said sensor is adapted to measure illuminance and so said threshold value is a light illuminance threshold. In this embodiment light having an illuminance greater than said light illuminance threshold is recorded in said memory. Moreover, for said specified time interval, the cumulative amount of time that light having an illuminance greater than said threshold is recorded in said memory and displayed on said display device. Ideally said threshold value is set at a transition point i.e. above the highest indoor recording for said light or at least one selected part of the visible spectrum and below the lowest outdoor recording for said light or the said selected part of the visible spectrum.

In a preferred embodiment of the invention the threshold value, representative of indoor versus outdoor light, is defined as 500 - 5000 Ix, ideally 950 - 1 ,500 Ix, most typically about 1 ,000 Ix and most preferably 1 ,000 Ix. Typically, said interval is a day and the said target value is a daily target between 2 and 4 hours, including all 1 minute intervals there between, per day with a range of 500 to 5000 Ix, including all 1 unit intervals there between. Most typically, though not exclusively, said target value is 3 hours and, ideally also, the light threshold is set at or about 1 ,000 Ix.

Additionally, or alternatively, said sensor is adapted to measure any one or more selected parts of the light spectrum, including any combination thereof. In this alternative instance the level of, for example, blue light indoors and outdoors is determined and a threshold value set representing a value representative of the difference between the two. Additionally, or alternatively, said sensor is adapted to measure UV light and so said threshold value is a UV light threshold. In this embodiment of the invention said UV sensor is ideally adapted to have its strongest response in the wavelength range 280-400nm. In all of the above embodiments of the invention the light sensor is calibrated such that said threshold value represents the dividing line between a selected type of light levels indoors and outdoors, thus serving as a cut-off for distinguishing between these two environments. Preferably light measured by said light sensor lower than said threshold is either recorded in said memory for the amount of time said light persists below said threshold or it is discarded, where it is recorded, ideally, within any specified time interval the cumulative amount of time that light lower than said threshold is recorded in said memory is displayed on said display device.

In a preferred embodiment of the invention the device of the invention is used to prevent myopia.

In yet a further preferred embodiment of the invention said time interval is a day or 24 hours, although larger periods may be also used to work the invention such as two or more days, including three, four, five or six days, or even a week or 7 days. In yet a further preferred embodiment of the invention said embedded software is set, or can be set, such that a daily target value is defined for said cumulative amount of time that light having a unit of measurement, such as illuminance, greater than said threshold is experienced. Moreover this target value is ideally displayed on said display device and the amount of time remaining in said time interval to achieve this target value is also displayed on said display device.

Reference herein to embedded software is to software held on the microcontroller in the device. In an alternative embodiment of the invention said device comprises a microprocessor with non-volatile memory wherein the device software resides on the non-volatile memory instead of being embedded in the microprocessor chip.

In a further preferred embodiment of the invention there is also provided with the device end-user software that enables a user to download data recorded on the device and/or connect said device to another computing platform whereby use of the device can be manipulated.

In a further preferred embodiment of the invention the instantaneous light level, such as illuminance, is displayed on said display device and ideally, also, said threshold value whereby a user can be aware of whether the instantaneous light value is above or below said threshold and also by what, if any, amount. Ideally, the display device is a small screen.

Preferably, the RTC can be used with the implementation of associated motivational features provided in the device. For example, where the daily target of outdoor time (preferably 3 hours) has not been met, the device provides feedback to the user either through the display or other features such as associated, LED indicators, audible devices (beeps), oscillatory devices (vibrations), tactile devices or otherwise. Further, preferably the RTC can also be configured to allow the device to track daylight hours based on the current date. Indeed, typical RTC chips allow time and date to be counted, including leap years. Hence, the daylight hours can be adjusted e.g. for winter versus summer. Thus, the RTC is further adapted to anticipate predictable changes in daylight such as those that vary with the seasons and geographical location. This preferred feature allows sophisticated motivational strategies to be implemented, where timely prompting can be provided by the device, with or without a user's intervention, to encourage outdoor activities. In a preferred embodiment of the invention said device comprises a wrist-worn device, or a badge-worn device.

More preferably still, the light sensor comprises a photosensor element, associated circuitry and serial communication interface. Preferably, the photosensor is chosen such that its spectral response is well-matched to the average response of a human eye (see for example, the CIE 2° Standard Observer [47] or the CIE 10° Standard Observer [49, 50]). In addition, the photosensor must be capable of distinguishing light illuminance values that are either below said threshold (typically less than or equal to 1 ,000 Ix), or above said threshold and hence representative of outdoors/protective against e.g. myopia (typically greater than 1 ,000 Ix). For this device, suitable light sensors are selected from the list comprising or consisting of: calibrated photodiodes, phototransistors, photoresistors, or any other photosensors that meet the above requirements. In a preferred embodiment of the invention monochromatic light detection can be achieved by either i) using a light sensor with a narrow spectral response centred at a particular colour or ii) using a colour filter in combination with a light sensor with a broadband response (e.g. a white light sensor).

In a preferred embodiment of the invention an analog signal from said light sensor is amplified prior to feeding the signal to the microcontroller. Ideally, for data logging, the photosensor signal is converted into a digital signal using an analog-to-digital converter (ADC) and the signal is then fed into an input pin on the microcontroller.

In yet a further preferred embodiment of the invention said embedded software is configured as per figure 3. Ideally, key parameters such as the light illuminance threshold value (THRESHOLD), the sampling interval for the light illuminance (SAMPLE_INT) and the number of samples used for averaging (SAMPLES) are specified within the microcontroller code. Ideally, the microcontroller samples the signals from the light sensor and calculates an "instantaneous" average light illuminance value (AVG_LIGHT). If the light illuminance reading changes from less than threshold to greater than threshold value, the microcontroller triggers an internal timer function (TIMER) and creates a timing object (T) that keeps track of how long the light illuminance has been continuously above the threshold. The cumulative light exposure time for the day, at above threshold levels, is also updated and stored in the memory (CUMEXP). To log the detailed data, a logging event is called by the microcontroller and the data (DATE, TIME, AVG LIGHT, CUMEXP) is written to the non-volatile memory. The display information is then updated with the instantaneous light illuminance and the cumulative exposure time.

For the case where the instantaneous light illuminance is lower than threshold, the complete data logging can be activated by turning on the "all data mode" (ALL DATA = TRUE). Alternatively, if data logging for low light levels is not required, then the display device is updated with the instantaneous light illuminance without data logging. The data logging features can be adjusted depending on a user's requirements. Reduced logging improves battery life while complete data logging is advantageous for clinical studies. The TIME and DATE values are obtained from the real-time clock for logging and display. If the TIME return value indicates that it is midnight, CUMEXP is reset to zero and then used for tracking cumulative light exposure for a new day. In a preferred embodiment of the invention said power supply is a battery either replaceable or rechargeable. Where a rechargeable battery is used the device comprises battery charging and protection circuitry for connection to an external power. In a further preferred embodiment of the invention said microcontroller embedded software further includes a method of calculating the remaining battery capacity with the battery life information relayed to a user via the display device. Ideally, for battery life extension, the embedded code can also be used to turn on or off specific device peripherals in order to minimize power consumption.

More preferably still, the device includes button switches in order to obtain user input. Specifically, the buttons can be used to set the time and date on the RTC, select information displayed on the display device and switch between different user modes. Additionally or alternatively, said device is adapted for touch-screen control using conventional software and associated circuitry. Ideally, the device includes customer or end-user software to allow device settings to be changed using a personal computer or any other computing platform.

Ideally also, to connect the device to a computing platform (e.g. a personal computer), the microcontroller is linked to a serial-to-USB converter. Additionally, or alternatively, the device also comprises a wireless transceiver to transfer data from the device.

According to a further aspect of the invention there is provided a method to treat or prevent myopia by motivating and increasing the amount of time an individual spends outdoors during the day comprising:

a) providing a wearable device to prevent myopia comprising:

at least one light sensor adapted to measure light;

at least one display device;

at least one Real Time Clock (RTC);

at least one power source;

a non-volatile memory;

a microcontroller or microprocessor; and

embedded software residing in the microcontroller and/or the non-volatile memory

b) setting said embedded software to define a light threshold;

c) recording light measured by said light sensor exceeding said threshold in said memory for the amount of time said light persists;

d) setting said embedded software to define a specified time interval; e) recording the cumulative amount of time that light exceeds said threshold, equivalent to time spent outdoors, during said time interval in said memory; and

f) displaying on said display device said cumulative amount of time that light exceeds said threshold.

Whilst the method has been described having regard to steps a) - f), it will be apparent that steps b) and d) can be set prior to a user wearing said device and, indeed, this will typically be the case.

In yet a first preferred method of the invention said time interval is a day or 24 hours, although larger periods may be also used to work the invention such as two or more days, including three, four, five or six days, or even a week or 7 days. In yet a further preferred embodiment of the invention said embedded software is set, or can be set, such that a target value is defined for said cumulative amount of time that light having a unit of measurement, such as illuminance, greater than said threshold is experienced. Moreover this target value is ideally displayed on said display device and, ideally, the amount of time remaining in said time interval to achieve this target value is also displayed on said display device. Typically, the target value is between 2 and 4 hours per day, including all 1 minute intervals there between, per day. Most typically, though not exclusively, said target value is 3 hours per day or approximately 3 hours per day. In a further preferred embodiment of the invention said sensor is adapted to measure illuminance and so said threshold value is a light illuminance threshold. In this ^' embodiment light having an illuminance greater than said light illuminance threshold is recorded in said memory. Moreover, for said specified time interval, the cumulative amount of time that light having an illuminance greater than said threshold is recorded in said memory and displayed on said display device. Ideally said threshold value is set at a transition point i.e. above the highest indoor recording for said light or at least one selected part of the visible spectrum and below the lowest outdoor recording for said light or the said selected part of the visible spectrum. In a preferred embodiment of the invention the threshold value, representative of indoor versus outdoor light, is defined as 500 - 5000 Ix, ideally 950 - 1 ,500 Ix, most typically about 1 ,000 Ix and most preferably 1 ,000 Ix.

Typically, said interval is a day and the sajd target value is a daily target between 2 and 4 hours, including all 1 minute intervals there between, per day with a range of 500 to 5000 Ix, including all 1 unit intervals there between. Most typically, though not exclusively, said target value is 3 hours and, ideally also, the light threshold is set at or about 1 ,000 Ix.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprises", or variations such as "comprises" or "comprising" is used in an inclusive sense i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

All references, including any patent or patent application, cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. Further, no admission is made that any of the prior art constitutes part of the common general knowledge in the art.

Preferred features of each aspect of the invention may be as described in connection with any of the other aspects.

Other features of the present invention will become apparent from the following examples. Generally speaking, the invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including the accompanying claims and drawings). Thus, features, integers, characteristics, components or devices described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein, unless incompatible therewith.

Moreover, unless stated otherwise, any feature disclosed herein may be replaced by an alternative feature serving the same or a similar purpose.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

An embodiment of the present invention will now be described by way of example only with reference to the following wherein: Figure 1 shows the average light levels for different indoor and outdoor activities;

Figure 2. shows a system block diagram for the novel device;

Figure 3. shows an embedded software flow chart for a method of implementing device key features;

Figure 4. shows a device in accordance with the invention in the form of a wrist wearable version;

Figure 5. shows the device when released from said wrist strap;

Figure 6. shows the device of Figure 5 when the front face has been removed and so shows the internal configuration;

Figure 7. shows the wrist strap to which the device of Figures 5 and 6 is attached;

Methodology

Light level as an effective means to distinguish daytime outdoor activity In our recent one-year Family Incentive Trial (FIT) study, 285 children aged 6-12 years were randomized to either the intervention (n=147) or control (n=138) arm [16]. We measured the time for outdoor and indoor activities of Singapore children by both a one-week diary and a portable light meter to measure light levels throughout the day. The 1-week outdoor activity diary was structured to track all activities during weekdays and weekends. The portable light meter contained a light sensor that recorded the amount and duration of exposure to white light illumination in lux (1 lumen per square meter) every 5 min from the beginning to the end of the day. In our pilot study, we have found that light level acts as an effective means to measure daytime outdoor activity. A threshold of light level, 1000 Ix, is proven to be effective to distinguish the time spent indoors or outdoors [16]. During the school term and school holidays, the mean time outdoors in the daytime from the diary was 5.44h per week and 7.91 h per week (P= 0.004), respectively. The mean time spent with light levels of greater than 1000 Ix from the light meter, were 7.08 h per week and 9.81 h per week (P<0.001), respectively [16]. Figure 1 depicts the average light levels for different indoor and outdoor activities during the day for a child [41]. The indoor light intensity levels were very low and most of the time less than 1 ,000 Ix, whereas there was a variation outdoors from tens of thousands of lux on a sunny day to a few thousand lux on cloudy days with an overcast sky.

Wearable activity-tracking devices motivate behavioral change

Wearable activity-tracking devices, such as pedometers, have achieved tremendous market success recently. Individuals may check the pedometer's display periodically and track the number of steps they have taken. With a daily recommended goal of 10,000 steps, pedometers encourage individuals to track their daily activity levels and it motivates them to maintain healthy fitness levels.

In the same way, parents who are anxious about the onset of myopia in their children are likely to want a wearable device that could prevent myopia by simply changing a child's behavior and so encourage more time outdoors.

Description of the present invention We have therefore developed a novel wearable device to record, indicate and motivate a wearers' daytime outdoor activity. The daytime outdoor activity is determined by setting a threshold value for the measured light illuminance level. The cumulative time in the day exposed to ambient light that is higher than the threshold level is recorded and displayed. In particular, the threshold value for indoor versus outdoor light is defined as 1 ,000 Ix in our recent pilot study in Singapore [16],.

A target value per day of the cumulative time spent outdoors in the daytime is set to encourage the overall amount of daytime outdoor activity. In particular, from the above FIT trial, children in Singapore currently spend about 1.5 h outdoors on a weekday and 2.5 h on a weekend [42]. In one embodiment we set our device to indicate a target of 3 hours outdoors per day.

The device can be also used in clinical trials to study the effect of outdoor activity on the development of myopia in children and also the effects of therapeutics or food supplements for treating or preventing myopia in children.

An example of the wearable device

One embodiment of the invention will now be described by way of example only. Those skilled in the art will appreciate that variations in the technical details may be undertaken to work the invention, in particular, features may be substituted for features having an equivalent effect and/or functionality. Notably, the invention comprises a wearable device [1] that logs outdoor time to prevent the development of myopia.

The device includes a system that is based on a microcontroller [2], which reads the light illuminance signal from a light sensor [3] through a serial communication bus. Figure 2 shows a system block diagram of the novel device. Using a light sensor [3], when the detected light illuminance is greater than an established threshold value (preferably 1 ,000 Ix), an illumination signal produced by said light sensor is generated, sampled, averaged (to reduce random noise) and then written into a built- in memory [4], together with the time, date and the amount of cumulative time spent exposed to said light illuminance greater than the established threshold value (preferably 1 ,000 Ix), in other words the cumulative amount of time spent outdoors for a given time interval e.g. that day.

Simultaneously, the instantaneous light level [5a] and the cumulative amount of time spent outdoors [5b] for that day are displayed on a small display device [5] for a user's convenience and feedback. To keep track of the date and time [5c], a realtime clock [6] (RTC) is integrated with the device. The RTC [6] enables the logging of cumulative light exposure [5b] and can also be used with the implementation of associated motivational features in the device. For example, where the daily target of outdoor time (preferably 3 hours) has not been met, the device provides feedback to the user either through the display, LED indicators, audible beeps, vibration (tactile feedback), or otherwise [5d]. Further, the RTC [6] also allows the device to track the daylight hours which varies with the seasons and geographical location. This allows sophisticated motivational strategies to be implemented, where timely user-feedback can be provided to encourage outdoor activities. The entire device is packaged in a wearable form [7], ideally suitable for children. As an example, a version of the device could be packaged in the form of a wrist-worn [7], as exemplified in Figures 4- 7, wearable sensor device [1]. More details on specific portions of the wearable device are given below.

Light Sensor Module

The light sensing module consists of a photosensor element [3], associated signal conditioning circuitry and serial communication interface (including but not limited to I2C, SMBus, SPI). The photosensor [3] is chosen such that its spectral response is well-matched to the average response for a human eye (see for example, the CIE 2° Standard Observer [43] or the CIE 10 ° Standard Observer [44, 45]. In addition, the photosensor [3] must be capable of distinguishing light illuminance values that are either below threshold (e.g. less than or equal to 1 ,000 Ix), or above threshold and hence protective against myopia (e.g. greater than 1 ,000 Ix). For this device, suitable light sensors include calibrated photodiodes, phototransistors, photoresistors, or any other photosensors that meet the above requirements. Depending on the photosensor chosen, signal amplification may be employed prior to feeding the signal to the microcontroller [2]. For data logging, the photosensor [3] signal is converted into a digital signal using an analog-to-digital converter (ADC) and the signal is then fed into an input pin on the microcontroller [2].

Embedded Software

The embedded software within the microcontroller is used to integrate all the components of the device into a coherent system. Figure 3 shows a flow chart of one method of implementing the key device features within the embedded software. Key parameters such as the light illuminance threshold value (THRESHOLD), the sampling interval for the light illuminance (SAMPLEJ T) and the number of samples used for averaging (SAMPLES) are specified within the microcontroller code. The microcontroller samples the signals from the light sensor and calculates an "instantaneous" average light illuminance value (AVGJJGHT). If the light illuminance reading changes from less than threshold to greater than threshold value, the microcontroller triggers an internal timer function (TIMER) and creates a timing object (T) that keeps track of how long the light illuminance has been continuously above threshold. The cumulative light exposure time for the day [5b], at above threshold levels, is also updated and stored in the memory [4] (CUMEXP). To log the detailed data, a logging event is called by the microcontroller [2] and the data (DATE, TIME, AVGJJGHT, CUMEXP) is written to the non-volatile memory [4]. The display information [5a-c] is then updated with the instantaneous light illuminance and the cumulative exposure time.

For the case where the instantaneous light illuminance is lower than threshold, the complete data logging can be activated by turning on the "all data mode" (ALL DATA = TRUE). Alternatively, if data logging for low light levels is not required, then the display device is updated with the instantaneous light illuminance without data logging. The data logging features can be adjusted depending on the user requirements. Reduced logging improves battery life while complete data logging is advantageous for clinical studies. The TIME and DATE values [5c] are obtained from the real-time clock [6] for logging and display [5]. If the TIME return value indicates that it is midnight, CUMEXP is reset to zero and then used for tracking cumulative light exposure for a new day. Power Source and Management

For the device to be wearable and portable [7], a battery power source [8] is included. The battery [8] used could be either single-use or rechargeable. If a rechargeable battery is used, the power module will also include battery charging and protection circuitry for connection to external power. An external DC power supply, either an AC-to-DC adapter connected to the mains, a standard 5V supply from a USB port, or otherwise can be used for device charging. The battery management system also includes a method of calculating the remaining battery capacity with the battery life information relayed to the user via the display device. In order to provide stable voltage levels to the device peripherals, voltage regulators will be implemented as required. If necessary, logic level shifters will be employed according to the specific peripheral requirements. For battery life extension, the embedded software code can also be used to turn on or off specific device peripherals in order to minimize power consumption. For user convenience, a backup battery (e.g. a coin cell) can also be included to keep the RTC [6] running even if the device power is cut off completely. Typical clock backup batteries last for several years and this means that the user need not re-set the time every time power is cut off. Memory and Data Storage

Non-volatile memory [4] (e.g. Flash or other non-volatile memories) is integrated within the device for the purpose of data logging. This allows data retention in the event that power is cut-off completely (e.g. due to a flat battery). The memory is connected to the microcontroller [2] via a serial interface to allow read and write operations to be triggered.

User Input and Feedback

The device includes button switches in order to obtain user input. Specifically, the buttons can be used to set the time and date [5c] on the RTC [6], select information displayed on the display device [5] and switch between different user modes. In addition, the device includes customer or end-user software to allow device settings to be changed using a personal computer or any other computing platform. The primary method of user feedback is visual, using a display device [5] (LCD, LED, OLED or otherwise) on the device. Critical information conveyed includes the cumulative hours of light exposure [5b] (at levels above threshold value), current time [5c], and number of daylight hours remaining. Another form of visual feedback could take the form of LED backlight on the display device corresponding to whether the daily light exposure target has been met [5d] (e g, green backlight for the case where the target has been met and red backlight for the case where the target has not been met). If desired, other methods of user feedback can be incorporated such as audible beeps (e.g. using a piezoelectric buzzer) or haptic feedback with vibration from a miniature motor (motor drive circuitry required).

Computing Platform Interface and User Software

To connect the device to a computing platform (e.g. a personal computer), the microcontroller is linked to a serial-to-USB converter. The user is then able to access the data that has been logged in the device using the customer or end-user software. The software facilitates automatic synchronization of data as well as data presentation in the form of charts. This allows children and their parents to review the child's daytime outdoor activity levels and set goals for further improvement, if necessary. If the device is used as a part of a clinical study, the software can also be used to forward data to clinicians via electronic mail. This reduces the amount of error in data logging compared to studies where manual diaries are used for data logging. If necessary, the custom software can be designed to enable storage of logged data on an online server (e.g. cloud storage), enabling seamless synchronization of data across multiple computing platforms (e.g. personal computers, laptops, smartphones, tablets etc.).

Apart from using a USB connection to transfer data from the device, a wireless transceiver can also be used [9]. A number of wireless technologies are available, including but not limited to Bluetooth, Infrared (IrDA), Wireless LAN and Zigbee. With a wireless-enabled device, a greater number of computing platforms can be used to access the logged data. For example, a smartphone running a device end-user software may use wireless data transfer to communicate with the device. Summary

We have developed a method and associated wearable portable outdoor-targeting device to prevent myopia. Our device is novel and, to our knowledge, has not been conceived before. Considering the high prevalence rate of myopia in Asia alone, there is an unmet need that is addressed by the provision of our device.

References

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Claims

1. A method to treat or prevent myopia by motivating and increasing the amount of time an individual spends outdoors during the day comprising:

a) providing a wearable device to prevent myopia comprising:

at least one light sensor adapted to measure light;

at least one display device;

at least one Real Time Clock (RTC);

at least one power source;

a non-volatile memory;

a microcontroller or microprocessor; and

b) setting said embedded software to define a light threshold;

d) setting said embedded software to define a specified time interval;

e) recording the cumulative amount of time that light exceeds said threshold during said time interval in said memory; and " f) displaying on said display device said cumulative amount of time that light exceeds said threshold.

2. The method according to claim 1 wherein said time interval is a day or a multiple thereof.

3. The method according to claim 1 or claim 2 wherein said embedded software is set, or can be set, such that a target value is defined for said cumulative amount of time that light having a value greater than said threshold is experienced during said time interval.

4. The method according to claim 3 wherein said target value is displayed on said display device.

5. The method according to any one of claims 1 - 4 wherein the cumulative amount of time under part e) is displayed on said display device.

6. The method according to any one of claims 1 - 5 wherein the cumulative amount of time under part e) is subtracted from said target value and displayed on said display device.

7. The method according to claim 6 wherein the amount of time remaining in said time interval to achieve said target value is also displayed on said display device.

8. The method according to any one of claims 1 - 7 wherein light measured by said light sensor below said threshold is either recorded in said memory for the amount of time said light persists below said threshold or it is discarded, and where it is recorded, within any specified time interval, the cumulative amount of time that light below said threshold is recorded in said memory is displayed on said display device.

9. The method according to any one of claims 1 - 8 wherein said light sensor is adapted to measure light selected from the group comprising: white light, UV Hght, blue light, infrared light and any one or more parts of the light spectrum, including any combination thereof.

10. The method according to any one of claims 1 - 8 wherein the threshold value, representative of indoor versus outdoor light, is a transition point represented by a point between the highest indoor recording for at least one selected part of the visible spectrum and below the lowest outdoor recording for said selected part of the visible spectrum.

11. The method according to any one of claims 1 - 10 wherein the threshold value, representative of indoor versus outdoor light, is selected from the group comprising: 500 - 5000 Ix; 950 - 1 ,500 Ix; about 1 ,000 Ix and ί,ΟΟΟΙχ.

12. The method according to any one of claims 1 -1 1 wherein said target value is between 2 and 4 hours, including all 1 minute intervals there between.

13. The method according to any one of claims 1 - 12 wherein said target value is 3 hours.

14. The method according to any one of claims 1 - 13 wherein an instantaneous light level, the level recorded in the instant of measuring, is displayed on said display device.

15. The method according to any one of claims 1 - 14 wherein said threshold value is displayed on said display device.

16. The method according to any one of claims 1 - 15 wherein the RTC is adapted to allow the device to track daylight hours, regardless of season or geographical location.

17. The method according to any one of the preceding claims wherein said embedded software is configured as shown in figure 3.

18. The method according to any one of claims 1 - 17 wherein the device is adapted to communicate with other computing equipment.

19. A wearable device to prevent myopia by motivating and increasing the amount of time a wearer spends outdoors during the day, comprising:

a) at least one light sensor adapted to measure light ;

b) at least one display device;

c) at least one Real Time Clock (RTC);

d) at least one power source;

e) a non-volatile memory ;

f) a microcontroller or microprocessor; and

wherein said embedded software is set, or can be set, to define a light threshold value whereby light measured by said light sensor exceeding said threshold is recorded in said memory for the amount of time said light persists and further wherein said embedded software is set, or can be set, so that within any specified time interval the cumulative amount of time that light exceeds said threshold is recorded in said memory and displayed on said display device.

20. The wearable device according to claim 19 wherein said light sensor is adapted to measure light selected from the group comprising or consisting of: white light, UV light, blue light, infrared light and any one or more parts of the light spectrum, including any combination thereof.

21. The wearable device according to claim 19 or 20 wherein said light sensor comprises a photosensor whose spectral response is well-matched to the average response of a human eye.

22. The wearable device according to claim 20 or claim 21 wherein the light sensor is capable of distinguishing light illuminance values that are above and/or below said threshold.

23. The wearable device according to any one of claims 20 - 22 wherein said light sensor is selected from the group comprising or consisting of: calibrated photodiodes, phototransistors and photoresistors.

24. The wearable device according to any one of claim 19 - 23 wherein the display device is a small screen.

25. The wearable device according to any one of claims 19 - 24 wherein the device comprises LED indicators, audible devices (beeps), oscillatory devices (vibrations) or tactile devices.

26. The wearable device according to any one of claims 19 - 25 wherein said power supply is a battery either replaceable or rechargeable.

27. The wearable device according to any one of claims 19 - 26 wherein the device includes buttons, switches or touch-screen control adapted to receive user input.

28. The wearable device according to any one of claims 19 - 27 wherein the device is adapted to communicate with other computing equipment.

29. Use of a device according to any one of claims 19 - 28 to prevent or treat myopia.

30. A microcontroller or microprocessor with non-volatile memory comprising embedded software for performing the method according to any one of claims 1 - 18.