## 2 Materials and Methods
### Measuring Visual Acuity  
Although the original LogMAR test requires 20 ft (6 m) distance between the patient and the chart, such spacious rooms are not always available; therefore, scaled options were developed for the distances of 4 m, 3 m, 2.5 m, and 2 m [24].  
Two charts, one Snellen and one LogMAR, were printed out in accordance with the scale required for 3 m distance measurements [9; 25] using high-contrast printing mode. Although the charts' printouts size was scaled in accordance with the standards, a quick checkup was performed: one of the authors of the article wears glasses with \(-\)2.50 D on the right eye and \(-\)1.50 D on the left eye. In accordance with the Snellen chart specification, the person with \(-\)2.50D eyesight should be able to see 20/200 letters size (line 1) and with \(-\)1.50D 20/100 letters size (line 2). Additionally, with glasses on (normal eyesight), a person must be able to distinguish 20/20 symbols (line 8). Keeping in mind that the conversion of visual acuity into dipoters is a far more complicated process, the checkup succeeded, and the ability to distinguish the symbols on the chart corresponded to the expected result.  
In most real-life cases, the choice of the chart is affected not only by its quality but also by the qualifications of the personnel, ease of use, and time spent on measurements. However, for this experiment, there was no time limit for a single measurement, and conversion into dipoters with a precision required for prescribing glasses was not required; therefore, both the Snellen and LogMAR charts were used in parallel for comparing OCR results that should give the same or similar values in accordance with the conversion table's data.  
The charts were placed on a white wall illuminated by fluorescent light bulbs. No considerable amount of natural light was present in the room. Illuminance was measured using the Sauter SO 200K digital light meter with a reading accuracy of \(\pm\)3% rdg \(\pm\) 0.5% f.s [26], with an average value of the measurements being with a value of 662 \(\pm\) 6 lux. This illuminance distribution is considered even. The authors defined deviation values of \(\pm\)10 lux as acceptable, and as long as measurement results are within the acceptable interval, their variations will not be considered.  
Fluorescent light bulbs have discrete emission spectrum with main peaks at 546 nm and 611 nm (Figure 1).  
Figure 1: Fluorescent lighting spectrum peaks.  
According to Sauter SO 200K lux meter technical specifications [26], its spectral sensitivity was sufficient for measuring illuminance in this wavelength range (Figure 2).  
The illuminance was measured (Figure 3) both at the beginning and the end of the measurement session, and the disparity fell within the acceptable limits.  
The color temperature was measured using the Pocket Light Meter app by Nuwaster studios [27] on an iPhone 13 Pro front camera [28] (Figure 4).  
Distance to the chart is measured by Duka LS-P laser distance measure with an error margin of 1 mm [29].  
The authors define distance measurement deviation of \(\pm\)10 cm (about 3.94 in) as acceptable and for as long as measurement results are within the acceptable interval.  
Out of three robots, Double 3 is the only one with an adjustable height that can be changes withing the range of 120-150 cm (3.94-4.92 ft). Temi camera is located 94 cm (about 3.08 ft) above the floor and Ohmni camera is located 140 cm (about 4.59 ft) above the floor. Middle position was chosen--120 cm that lies within Double 3 height range. Temi and Ohmni TPRs can tilt the camera for the charts to be in the center of the camera viewing field, which is important for measurements in zoom mode.  
Figure 3: Measuring the illuminance of the visual acuity charts.  
Figure 2: Sauter SO 200K lux meter’s spectral sensitivity.