# User Friendliness of a Wearable Visual Behavior Monitor for Cataract and Refractive Surgery
## 2 Materials and Methods
VBM (Figure 1) incorporates the following sensors: Two optical time-of-flight distance sensors directed forward and 30\({}^{\circ}\) downward, ambient light sensor with separate red, green, and blue channels directed forward, combined ultraviolet and ambient light sensor directed upward, as well as motion and orientation sensors: Accelerometer, gyroscope, and magnetometer. The VBM does not include imaging sensors, such as cameras and location sensors, and does not infringe on the privacy of the wearer and other people. The VBM features an energy-independent real-time clock for reliable timestamping of the measurements. Measurements data are stored in the encrypted format in the device and the progress of data collection is shown on the embedded screen or on the screen of the station in hours and minutes. The onboard memory capacity is more than 1000 h. The VBM is charged overnight and the battery capacity is sufficient for a complete day of continuous measurements. When the device is returned to the clinic, data are transferred from the device to an electronic tablet and then uploaded to the internet server (cloud), decrypted, processed, and visualized via web-interface. Cloud processing is performed by advanced machine learning algorithms, which are trained to recognize various types of patient's visual activities, such as looking on a desktop computer screen, reading handheld materials, driving a car, and viewing objects at a distance. The environment is further analyzed based on the recognized activities to derive relevant metrics such as viewing distances to the objects of visual activities, such as distance to a computer screen, to a desktop, or to handheld material. The data are further aggregated to create relevant statistical representations. The VBM is intended to provide behavioral information to the attending HCP and to support ophthalmic surgeons or other healthcare professionals in the planning of cataract and refractive surgery. This is expected to improve participant satisfaction through the objective evaluation of individual vision needs and allowing practitioners to more adequately address those needs. Based on the individual  
Figure 1: Visual Behavior Monitor (VBM) fixed on the spectacles. profile of viewing distances, it is possible to select the optimal IOL solution by overlaying the defocus curve of the IOL, representing the expected visual acuity as a function of defocus (visual distance). Additional measured parameters, such as typical light levels and their spectral content, can be also considered. For example, monofocal IOLs deliver good far vision but cannot provide clear vision in near and intermediate distance zones, while lenses with advanced optics, such as bifocal and trifocal (multifocal) lenses, as well as lenses with an extended depth of focus, are capable of providing sufficient visual acuity and spectacle independence both in the near and intermediate zones, depending on the lens. At the same time, advanced optics can cause halos and glare in low-light conditions. Thus, for a patient with far distance vision needs with a large share of low-light activities, such as night driving, it would be reasonable to recommend a monofocal lens or blended vision solution, while an advanced optics IOL would be preferable for the patient with a range of activities with the viewing distance distributed between all vision zones and requiring often switching between zones. The information provided by the VBM allows healthcare professionals to objectively assess the needs of the patient and explain the benefits and limitations of the available solutions to the patient. However, the decision should include other factors, like personal preferences of the patient and tolerance to the multifocality of IOLs with advanced optics, as well as other conditions and, thus, should not exclude discussion with the patient. The measuring elements used in the VBM are standard components. Furthermore, the VBM is not intended to replace state-of-the art diagnostic methods in refractive treatment.