# Parafoveal and Perifoveal Accommodation Response to Defocus Changes Induced by a Tunable Lens
## 5 Conclusions  
In this study, we reported on an automated monocular system to measure accommodation to annular stimuli projected on the parafovea and the perifovea in response to random step defocus changes induced by a current-driven tunable lens. The accommodative response time increased gradually with increasing eccentricity, while the amplitude  
Figure 6: Parafoveal and perifoveal (**a**) reaction and (**b**) response times for different defocus step changes in the TL (arranged from lower to higher steps) for subject #1.  
decreased gradually and became negligible at 7\({}^{\circ}\) radial distance and beyond. For a 3 mm limited-eye pupil, defocus is the dominating Zernike coefficient, with no significant contribution from higher-order aberrations. Our experimental results clearly show that the amplitude of accommodation reduces with increased eccentricity, which can possibly be linked to the reduction in cone density and thus to a contrast reduction caused by the leakage of light from the outer segments [42]. Moreover, no evidence of a different accommodative response was found between subjects of different refractive errors in this study, which agrees well with previous findings [10; 43]. We are conducting further research to understand the mechanisms that trigger the correct direction of accommodation and thus the detection of the sign of defocus in the young adult eye both in foveal and parafoveal vision, as this ultimately may relate to myopia and the emmetropization process [44; 45]. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app13158645/s1](https://www.mdpi.com/article/10.3390/app13158645/s1)]([https://www.mdpi.com/article/10.3390/app13158645/s1](https://www.mdpi.com/article/10.3390/app13158645/s1)), Figure SI: Induced defocus sequence by the TL (black line) and accommodation response (red line) as a function of time for subject #3 for increasing radial eccentricity from 1\({}^{\circ}\) to 8\({}^{\circ}\). The induced defocus is shown with opposite sign to ease comparison; Figure S2: Individual Zernike coefficients in response to induced TL defocus changes for subject #1 for defocus \(Z_{4}\) (red line), astigmatism \(Z_{3}\) and \(Z_{5}\) (brown and blue lines), and spherical aberration \(Z_{12}\) (orange line); Figure S3: Induced defocus sequence by the TL (black line) and accommodation response (red line) as a function of time for subject #5 for increasing radial eccentricity from 1\({}^{\circ}\) to 8\({}^{\circ}\). The induced defocus is shown with opposite sign to ease comparison; Figure S4: Schematic of setup to test Zernike coefficient changes in response to defocus changes of the TL monitored in a plane that is conjugate to the HS-WFS. An expanded collimated HeNe (633 nm) laser beam was used for the illumination. The iris was set to a beam diameter of 4.5 mm corresponding to the largest eye pupil used in this study; Figure S5: Changes of Zernike coefficients as a result of a random sequence of defocus changes generated with the TL as measured with the HS-WFS including up to 4 th radial Zernike order. In (a) astigmatism (\(Z_{3}\), \(Z_{5}\)), defocus (\(Z_{4}\)), spherical (\(Z_{12}\)), and coma (\(Z_{7}\), \(Z_{8}\)) are all included on a common scale. In (b) defocus has been removed, and the vertical scale adjusted to reveal minute changes in the remaining Zernike coefficients when defocus changes; Figure S6: Analysis of blink removal with a MatlabTM code using (a) raw defocus data from the HS-WFS to obtain the (b) blink-filtered results. In (c) the difference between raw data and blink-corrected data shows no significant impact outside of the blink-induced spikes. Note that the sign of TL response has not been swapped here as it is in the main manuscript. Conceptualization, B.V., N.S. and L.L. ; methodology, B.V. and N.S. ; software, N.S. and B.V.; validation, B.V., N.S., L.L., P.P. and D.R. ; formal analysis, N.S. and B.V.; investigation, N.S. and B.V.; resources, B.V. and N.S. ; data curation, N.S.