## 3 Results
### Comparison of the Dynamic Accommodative Response and the Pupil Size at Different Viewing Distances  
This experiment set two viewing distances, namely, 0.4 m away from the object and 2.285 m in front of the subjects' eyes through the double-mirror system. The changes in dynamic accommodative response and pupil size were detected and compared, as shown in Figure 4. The results show that the mean value of the accommodative response was 1.69 \(\pm\) 0.31 D when the viewing distance was 0.4 m, while it was 0.11 \(\pm\) 0.05 D when the viewing distance was 2.285 m through the double-mirror system, and the accommodative response showed a significant difference between gazing at 0.4 m and 2.285 m (\(p\) < 0.001). The pupil size was 3.79 \(\pm\) 0.49 mm and 4.09 \(\pm\) 0.72 mm when the viewing distances were 0.4 m and 2.285 m, respectively, and a significant difference was also found in the pupil size (\(p\) < 0.001).  
Figure 4: Comparison of (**a**) accommodative response and (**b**) pupil size at the two viewing distances of 0.4 m and 2.285 m.  
As indicated by the above results, compared to the double-mirror system imaging, the accommodative response was larger and the pupil size was smaller when the subjects looked at a closer distance; on the other hand, when the viewing distance increased from 0.4 m to 2.285 m (double-mirror system imaging), the accommodation response was reduced, and the pupil size was enlarged. At a viewing distance of 2.285 m, the accommodation could be relaxed by using the double-mirror system. The larger pupil size also reflects a reduction in accommodation.  
To understand the effect of the double mirror system on the accommodative response, we compared the accommodative response of directly looking at the real object, looking at the virtual image through a single plane mirror at various viewing distances from 0.4 m to 2.285 m, and looking at the virtual image at 2.285 m through the double-mirror system, as shown in Table 2 and Figure 5. Since the viewing distance of the double-mirror system is fixed, there is only one accommodative response at 2.285 m. The accommodative response varies with the viewing distance in these three ways and is presented in Table 2. When the subjects were looking directly at the real object and looking at the image through a single plane mirror, the accommodative response decreased with the increase of the viewing distance from 0.4 m to 1.6 m. When the viewing distance reached 2.285 m, the accommodative response of the above two observation methods was very close to the accommodative response obtained by the double mirror system, which was about 0.11 \(\pm\) 0.05 D. The pupil size increased significantly with a viewing distance from 0.4 m to 0.6 m. When the viewing distance reached 1.2 m, the pupil size decreased significantly. When the viewing distance reached 2.285 m, the above two observation methods were very close to the pupil size obtained using the double mirror system, which was about 4.19 \(\pm\) 0.07 mm. The results indicate that the accommodative response and pupil size are consistent throughout these three methods at a viewing distance of 2.285 m. The advantage of this optical design is that the object can be seen at a longer distance, and the enlarged image is easier to observe. Compared to single plane mirror imaging, the image is in the opposite orientation, from left to the right, and the double-mirror system has no such problem.