# User Friendliness of a Wearable Visual Behavior Monitor for Cataract and Refractive Surgery
## 2 Materials and Methods
Nevertheless, it is very important to have hard facts to support the choice of IOL suitability or surgical method. Patients use the VBM in their normal daily routine, with the only excluded activities being those that involve water exposure of the wearable. Some other activities may be exempt based on a benefit/risk assessment. Those activities are meant to be communicated verbally to the attending HCP during pre-operative interview. A dedicated tablet is provided to the clinics for measurement data upload on the cloud and data review. The embedded cellular data module of the tablet is used for data upload and report review on the cloud, independent of the clinic's infrastructure. The clinic has access to a detailed report of all data the VBM collects. A simplified patient report including recommendations is available for the patient. The healthcare professional has an option to review aggregated metrics of visual behavior of the patient. For example, the viewing distance from all measurement days, collected by the patient, can be displayed as a histogram of the additional optical power (refraction) of the eye required to accommodate the objects of visual activity (Figure 2). Further, it is possible to relate the viewing distances to the particular head inclinations in order to visualize viewing distances in a two-dimensional plane (Figure 3). Such visualization is helpful to educate patients on the relation of activities and visual distances as visual zones can be linked to the actual physical space. Additionally, the system allows us to review activities chronologically, as performed by the patient during the selected measurement day. The distribution of viewing distances can be overlaid with other relevant parameters, such as ambient light exposure (Figure 4). This kind of plot allows the demonstration of viewing conditions during various activities to the patient. The time of the day information helps the patient to relate his or her daily routine to the measurements and communicate to the HCP the importance of certain activities. The HCP is also able to relate viewing distance to other parameters. Figure 5 demonstrates the history of ultraviolet light exposure during the study day together with ambient light, which provides additional information about the patient's lifestyle. The study has been conducted by five sites in three European countries: Germany, Switzerland, and Ireland (Table 1). A total of 129 patients were enrolled between August 2018 and May 2019. Patient age ranged from 49 to 82 (mean: 65). In all cases, the VBM measurement was performed before cataract surgery. Figure 3: Mapping of viewing distances on two-dimensional plane using head flexion information (Patient A). Dense areas reflect the computer work and handheld devices. Color coding for the vision zones is the same as in Figure 2.  
Figure 2: Distribution of viewing distance and required additional optical power of the eye (refraction) to observe objects of visual activity. The plot demonstrates domination of the intermediate viewing distance related to the computer work at around \(-\)1.75 D (0.57 m) for the particular patient (Patient A). Color coding is used to display the viewing zone, with green representing near viewing distances, blue representing intermediate, and yellow representing far. Figure 4: Example of the viewing distances and ambient light measurements with VBM during a day (Patient B). The example demonstrates the clear domination of far distances (upper plot), which is a marked difference in visual behavior from Patient A.