Visual Environment Evaluation Tool (VEET) Technical Overview
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The Visual Environment Evaluation Tool (VEET) is a pair of temple arms that gather quantitative data on characteristics of light near the eye without disrupting the wearer’s normal activities. Each temple arm is an independent instrument that uses state-of-the-art sensors to measure illumination intensity, spectrum, optical distance to near objects, and motion.
The VEET is intended for researchers studying human ocular development in controlled experiments and studies under supervision of their Institutional Review Boards (IRBs) or equivalent. The VEET is not intended for sale, general distribution, or use in clinical settings.
Why the VEET?
Current myopia research1 has demonstrated the role of extended visual experience in healthy ocular development. Optical cues and the spectrum, intensity, and temporal characteristics of light landing on the retina are all known factors affecting the development of the eye. However, there is still limited understanding as to which of these extrinsic factors are most important or how they interplay with intrinsic physical and neural differences between individuals.
Identifying the most consequential contributing factors has been challenging. Since ocular development continues until an individual is around 20-21 years of age, studies must be longitudinal and purely observational to respect participants’ privacy. Furthermore, existing research methodologies have severe limitations: subjective reporting correlates poorly with objective measurements, and current-generation devices for measuring visual experience are rudimentary, unreliable, and introduce privacy concerns.
The VEET addresses all of these challenges by integrating the highest quality spectral, luminance, movement, and distance sensors into a robust, lightweight, all-day-wearable form factor. To preserve the wearer’s privacy, there are no cameras or microphones: all the VEET measures is the light being reflected back from the environment.
Improved research tools such as the VEET ican enable researchersto better understand the impact of environmental inputs on myopia development and inform scientific models of eye growth.
VEET Benefits
Stable Form Factor
The VEET sensors are integrated directly into temple arms that connect to the wearer’s glasses frames. This provides stability and consistency of placement—as close to the eye as possible.
Frame Compatibility
The VEET is compatible with commercially available glasses frames.
Easy Setup
The VEET does not require post-delivery calibration—simply keep the optical glasses clean.
Locally Stored Data
The data stays on the device and is directly accessible to the researcher only through a standard USB connection. No accounts are required to access it.
Unfiltered Data Access
Each sensor’s data output is fully exposed, allowing calculations to be confirmed or post processed for specific purposes.
Privacy-Centered Design
The VEET has no camera, no microphone, no bluetooth or wifi connectivity, and does not record any personally identifying information. The device gathers data without compromising the wearer’s privacy or comfort.
Robust Sensors
The VEET is equipped with expanded sensing compared to existing devices including:
- Range sensing up to 2 meters over a 64 point grid
- 8 channel narrow color sensing for SPD reconstruction
- Reliable Lux values from 0.1 to 100,000+
Continuous Data Logging
Each VEET temple arm comes with a battery that supports all-day use. If charged daily, the VEET has a data storage capacity of more than one year. Data is continuously logged at pre-configured rates whenever battery reserves are available or the device is charging on wall power.
Sensing Technical Details
Each VEET temple arm incorporates robust, industrially proven solid-state sensors: the Time of Flight Sensor, Ambient Light Sensor, Spectral Light Sensor, and Inertial Measurement Unit.
In aggregate, the VEET sensors record information about the visual environment of the wearer, such as the environmental illumination, saturation and spectrum of colors. Additionally, they include range-finding for measuring the distance of objects in the wearer’s field of view).
Time of Flight Sensor
The Time of Flight Sensor (ams OSRAM, TMF8828) measures distance to near objects in millimeters (mm). It illuminates the nearfield environment with an infrared light and measures the time it takes for the light to return from reflected objects, reading 64 points on an 8 x 8 angular grid with a 41 degree x 52 degree FOV, converting this directly to distance in mm. Under typical indoor conditions, the maximum sensing distance is approximately 2 meters.
Ambient Light Sensor
The Ambient Light Sensor (ams OSRAM, TSL2585) provides photometric data directly in lux. It includes UVA and light flicker detection. The normalized response of the spectral sensor can be found in the manufacturer’s datasheet.
Spectral Sensor
The Spectral Sensor (ams OSRAM, AS7341) measures relative light intensity in 8 narrow band optical channels over the visible spectrum in addition to full spectrum clear and NIR sensing. This enables post-processing estimates of spectral power distribution and correlated color temperature. It has a 11-channel multi-spectral sensor for color detection and spectral analysis from approximately 350nm to 1000nm. The wavelength response of the spectral sensor can be found in the manufacturer’s datasheet.
Inertial Measurement Unit
The Inertial Measurement Unit (Bosch, BMI270) measures movement and orientation with a three-axis accelerometer and three-axis gyroscope. The Inertial Measurement Unit (IMU) is housed in the temple arm body and is not affected by the pointing angle of the other sensors.
Sensor Orientation
To cover a range of potential gaze behaviors, the right temple arm’s sensors are aimed 20 degrees downward and 4 degrees towards the sagittal plane while the left temple arm’s sensors are perpendicular to the glasses frame.
Researcher Experience
Easy to Configure
VEETManager software is compatible with Windows and MacOS operating systems, and provides a graphical user interface for configuring the data logging intervals and previewing sensor data.
Easy to Access Data
When it’s time for a researcher to unload data from the device, they connect it to a PC or Mac via USB-C and it shows up as a simple disk drive. The data is recorded as time series data in a non-proprietary Comma Separated Value (.csv) file.
Reusable
The VEET is designed to handle the rigors of typical daily wear. Each device can be reused by other research participants for different studies. It is safe to clean with typical optical cleaning solutions and isopropyl alcohol wipes.
Technical Specifications
The VEET is simple to wear and charge, and has a privacy-first design, to allow for all-day data logging.
Size and Weight
- Height: 2.0 cm
- Width: 1.4 cm
- Depth: 8.0 cm (excluding temple arms extensions)
- Weight: ~20 grams per VEET temple arm
Fit Compatibility
- Compatible with commercially available glasses frames (4 hinge designs provided)
- Exchangeable temple arm extensionallows for lengths typical of glasses (~125mm to 145mm)
- Accommodates users ages 7 and above
Sensors
- Time of Flight Sensor
- Ambient Light Sensor
- Spectral Light Sensor
- Inertial Measurement Unit
- Sampling rate: Maximum sampling rate is 1/2hz (sampled every 2 seconds) for all sensors. Each sensor is individually configurable.
Battery and Power
- Built-in 350mAh rechargeable lithium-polymer battery
- Charges over a standard 5V USB connection with a max current draw of 175mA
- Battery is fully charged in <2 hours on wall power
- >24 hours of data logging on one battery charge.
Capacity
- 16 GB Flash memory storage
- Holds months of logged data*
Input and Output
- USB Type-C connection
External buttons and controls
- None (to prevent research participants from accidentally interfering with data logging)
Mac system requirements
- Mac computer with USB 2.0 port
- Mac OS X Sonoma (v14) or later
Windows system requirements
- PC with USB 2.0 port
- Windows 10; or Windows 11
Timekeeping
- Time is synchronized with the PC when connected
- Time may differ between temple arms by several seconds
- Clock will be maintained for >1 month after the device goes into its low power mode
Environmental Requirements
- Non-charging use: -10ºC to 37ºC (98oF) and up to 95% humidity, non-condensing
- Charging or connecting to a computer: Below 27ºC (80ºF)
*When the device is in continuous use, unload data weekly to keep file size manageable.
1 Huang, H. M., Chang, D. S. T., & Wu, P. C. (2015). The association between near work activities and myopia in children—a systematic review and meta-analysis. PloS one, 10(10), e0140419.