Optimization of Virtual Shack-Hartmann Wavefront Sensing

Virtual Shack–Hartmann wavefront sensing (vSHWS) can flexibly adjust parameters to meet different requirements without changing the system, and it is a promising means for aberration measurement. However, how to optimize its parameters to achieve the best performance is rarely discussed. In this work, the data processing procedure and methods of vSHWS were demonstrated by using a set of normal human ocular aberrations as an example. The shapes (round and square) of a virtual lenslet, the zero-padding of the sub-aperture electric field, sub-aperture number, as well as the sequences (before and after diffraction calculation), algorithms, and interval of data interpolation, were analyzed to find the optimal configuration. The effect of the above optimizations on its anti-noise performance was also studied. The Zernike coefficient errors and the root mean square of the wavefront error between the reconstructed and preset wavefronts were used for performance evaluation. The performance of the optimized vSHWS could be significantly improved compared to that of a non-optimized one, which was also verified with 20 sets of clinical human ocular aberrations. This work makes the vSHWS’s implementation clearer, and the optimization methods and the obtained results are of great significance for its applications.

The Distribution of IOL Center and Its Relationship with Internal Ocular Objective Visual Quality in Cataract Patients

Background: To investigate the distribution of the center of the intraocular lens (IOL) after phacoemulsification, and to assess the correlation between the center of IOL and preoperative angle kappa, angle alpha, and objective internal visual quality, respectively, in cataract patients with monofocal and bifocal IOLs implantation. Methods: Prospective cross-section cases series. One hundred and thirty-seven eyes of 107 patients who underwent phacoemulsification were included. Preoperative angle kappa and alpha, postoperative internal ocular aberrations, internal objective visual quality, and the center of IOL relative to the visual axis (CIV) was evaluated using iTrace system. Independent sample t-tests and Pearson correlations were performed.Results: Locations of CIV were scattered in all directions centered on corneal light reflection for both C-Loop designed IOL and plate-haptic designed IOL. No correlations were found between CIV and preoperative angle kappa and alpha in both magnitude and orientation. No correlations were found between CIV and postoperative internal ocular aberrations (astigmatism, coma, and trefoil). In the bifocal IOLs group, the CIV was negatively correlated to the internal Strehl ratio at 3mm; however, it was not correlated to the Strehl ratio at 5mm. The magnitude of CIV was positively correlated to the length of the optic axis.Conclusions: CIV was not predictable according to angle kappa and alpha before cataract surgery. CIV was not related to internal ocular aberration, but large CIV may lead to light scattering due to steps between diffractive rings in patients with small pupil sizes. The magnitude of CIV may be greater in cataract patients with longer optic axis.Trial registration: retrospectively registered.