# Parafoveal and Perifoveal Accommodation Response to Defocus Changes Induced by a Tunable Lens
## 3 Experimental Results  
The response to the random step sequence for subjects #1 and #2 (emmetrope and mild myope) is shown in Figure 2. For both observers, defocus changes are followed closely both during accommodation and relaxation at 1\({}^{\circ}\) radial eccentricity. From 2\({}^{\circ}\) to 6\({}^{\circ}\) eccentricity, accommodation and relaxation are in the expected direction but with a reduced response with increasing eccentricity, which agrees with earlier studies [10; 12; 22; 23]. At and beyond 7\({}^{\circ}\) eccentricity, the accommodative response becomes negligible. The other mild myopic participant, subject #3, showed the same tendency (see Figure S1 in the supplementary document). An extra step (7.5\({}^{\circ}\)) between 7\({}^{\circ}\) and 8\({}^{\circ}\) radial eccentricity was taken to monitor the response closely at the point where accommodation is absent. Figure 3 shows the mean accommodative response for all subjects determined for the interval of 11-19 s (induced defocus ranged from \(-1.16\) D to \(-2.10\) D depending on the individual) as a function of stimulus eccentricity for all six subjects. The accommodative response decreases with higher eccentricities, although some variations are noticeable, e.g., for subjects #2 and #3, at 3\({}^{\circ}\) eccentricity, defocus went up compared to 2\({}^{\circ}\), and the in case of myopic subject #6, more variations were noticed at 4\({}^{\circ}\), 6\({}^{\circ}\) and 7.5\({}^{\circ}\), which can be caused by overshooting or accommodation. The accommodative range and initial position differ between subjects as expected based on Table 1.  
Figure 2: Induced defocus sequence by the TL (black line) and accommodation response (red line) as a function of time for subjects (**a**) #1 and (**b**) #2 with increasing radial eccentricity from 1\({}^{\circ}\) to 8\({}^{\circ}\). The induced defocus is shown with opposite signs to ease comparison. To estimate the difference between accommodative response and induced defocus, further analysis was performed. Table 2 shows these results at the time interval of 0-110 s and radial eccentricities in the range of 1-8\({}^{\circ}\) together with the average for all subjects. A low value means that the response followed the induced defocus well. Except for subject #3, all subjects showed a gradual decrease in accommodative response with eccentricity. Subject #3 is the oldest of the subjects, and therefore the range and drop-off with eccentricity is smaller. On average, the accommodative response flattens out for radial eccentricities of 7\({}^{\circ}\) and beyond. To determine whether other Zernike terms were affected, selected coefficients are shown in Figure S2 for subject #1. As expected with a small 3 mm pupil, the defocus term dominates the response, although careful comparison does reveal that astigmatism \(Z_{3}\) changed with the same sign as \(Z_{4}\), whereas astigmatism \(Z_{5}\) and spherical aberration \(Z_{12}\) changed with the opposite sign. This tendency was also noticed with foveal accommodation for pupil sizes up to 4.5 mm [19]. In some cases, coma \(Z_{7}\) and \(Z_{8}\) (not shown for simplicity) changed too, but only slightly (less than 0.2%), with the same sign as \(Z_{4}\). In all cases, defocus alone accounts for more than 99% of the total response with a small pupil. Figure 4 shows the accommodative response for myopic subjects #4 and #6. As emmetropes and mild myopes, myopic subjects were also able to track changes to the TL in the correct direction at up to 6\({}^{\circ}\) perifoveal vision, albeit with reduced response. At 7\({}^{\circ}\) and beyond, no response was observed (same for myopic subject #5; shown in Figure S3). The refraction by the spectacles impacts the field of view. However, for most subjects, this is a modest effect. With a vertex distance of 14 mm and for the most myopic subject (#6), wearing \(-6\) D correction equals an 8% reduction in field size (or 7.3\({}^{\circ}\) for the 8\({}^{\circ}\) target).