Explore the vast range of titles available.

A light-field camera captures both the intensity and the direction of incoming light1–5. This enables a user to refocus pictures and afterwards reconstruct information on the depth of field. Research on light-field imaging can be divided into two components: acquisition and rendering. Microlens arrays have been used for acquisition, but obtaining broadband achromatic images with no spherical aberration remains challenging. Here, we describe a metalens array made of gallium nitride (GaN) nanoantennas6 that can be used to capture light-field information and demonstrate a full-colour light-field camera devoid of chromatic aberration. The metalens array contains an array of 60 × 60 metalenses with diameters of 21.65 μm. The camera has a diffraction-limited resolution of 1.95 μm under white light illumination. The depth of every object in the scene can be reconstructed slice by slice from a series of rendered images with different depths of focus. Full-colour, achromatic light-field cameras could find applications in a variety of fields such as robotic vision, self-driving vehicles and virtual and augmented reality.A metalens array of GaN nanoantennas is used to make a full-colour achromatic light-field camera.

A theoretical possibility of improving the focusing quality of electron beams in an immersion objective by taking into account spherochromatic aberrations of the third order is considered. In this case, the resolution of the immersion objective is increased by reducing its total aberration by mutual correction of spherochromatic aberrations of the second and third orders. It is shown that when taking into account spherochromatic aberrations up to and including the third order and statistical regularities of electron emission, the radius of the electron beam scattering circle in the plane of the Gaussian image of the immersion objective decreases by almost an order of magnitude (by 6.75 times) and, accordingly, its resolution increases by the same amount. For the first time, focusing properties of a three-electrode immersion objective consisting of a flat cathode and two coaxial cylinders of equal diameter separated by gaps of finite width have been calculated taking into account spherochromatic aberrations up to and including the third order and statistical regularities of electron emission. In this case, the ratios between the sizes of the electrodes of the immersion objective and potentials on them are consistent with the parameters of electron emission.

Purpose To compare the clinical outcomes of myopiacorrected with corneal-wavefront-guided (CWG) laser in situ keratomileusis (LASIK) with AMARIS 1050S (SCHWIND eye-tech-solutions GmbH & Co. KG) and corneal-topography-guided (CTG) LASIK with WaveLight EX500 (Alcon Laboratories, Fort Worth, TX). Methods In this prospective, pseudo-randomized expanded cohort study, a total of 266 patients were subjected to binocular LASIK surgery, either with WaveLight EX500 (WaveLight group) or Amaris 1050S (AMARIS group) platforms. Data related to right eyes were selected for analysis. Corneal higher-order aberration (HOA) was selected as the primary endpoint; while visual acuity and refraction were the secondary endpoints. All the endpoints were assessed at 3 months postoperatively. Results There were 134 eyes in the AMARIS group and 132 eyes in the WaveLight group. After 3 months of postoperative follow-up, spherical and coma aberrations were significantly lower ( P  < 0.05) in the WaveLight group (spherical aberration: − 0.104 ± 0.199 µm; coma aberration: − 0.117 ± 0.202 µm) in comparison with the AMARIS group (spherical aberrations: 0.254 ± 0.146 µm; coma aberrations: 0.316 ± 0.297 µm). In the AMARIS group, 96.3% of the eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 while in the WaveLight group, 96.2% of the eyes achieved an UDVA of 20/20. Furthermore, the mean postoperative manifest refraction spherical equivalent (MRSE) was − 0.02 ± 0.28 in the AMARIS group and − 0.05 ± 0.21 in the WaveLight group ( P  = 0.34). Conclusions Both WaveLight EX500 and Amaris 1050S LASIK showed excellent refractive and visual outcomes. In addition, the WaveLight group showed minimal spherical and coma aberrations when compared to the AMARIS group.

Purpose: To determine the magnitude of higher order aberrations (HOAs) induced from light delivery device treatments after implantation of a light adjustable lens (LAL; RxSight). Methods: Patients who underwent cataract surgery or refractive lens exchange with LAL implantation in a private practice were included in this retrospective, consecutive chart review. The iTrace (Tracey Technologies) was used to measure corneal, internal, and total HOAs before each adjustment and lock-in visit at a 3-mm entrance pupil size. HOAs were also measured after the final lock-in visit. Overall and individual HOAs that were induced throughout the course of the LAL treatments were measured. Subgroup analysis was performed analyzing number of adjustments, distance versus near target, spherical aberration induced, target proximity, and history of refractive surgery. Results: This study included 56 eyes from 32 patients. The mean induction of total HOAs (combined corneal and internal aberrations) was −0.005 μm (standard deviation = 0.071). No induced total HOAs were greater than 0.3 μm. The 32 eyes that had undergone prior refractive surgery were found to have a statistically significant increase in induced HOAs compared to the 24 eyes without prior refractive surgery (P = .02). No other statistically significant differences were detected during subgroup analysis. Conclusions: This study suggests that LAL treatments do not induce a clinically significant amount of HOAs. However, eyes that have previously undergone refractive surgery may be more likely to have a greater magnitude of HOAs induced by light delivery device treatments.

PurposeTo evaluate the changes in the accommodative response and in the corneal and internal spherical aberration during 3 months of wear of orthokeratology lenses from the baseline.MethodsFifty children aged 8 to 17 were recruited for a prospective study and were fitted with orthokeratology lenses. Refraction without cycloplegia, high and low uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), accommodation lag, horizontal near phoria without correction, corneal topography, corneal, and total wavefront aberration were performed at baseline, 1 day, 1 week, 1 month, and 3 months. Data were analyzed by Student’s t test for related samples, repeated measures ANOVA test, and Pearson correlation test.ResultsThe spherical equivalent (SE) before and after 3 months was − 3.33 ± 1.60 D and − 0.30 ± 0.46 D, respectively. Accommodation lag was 0.53 ± 0.38 D and 0.20 ± 0.33 D at baseline and at 3 months, respectively. A moderate correlation between lag at the baseline and its change between baseline and the 3-month visit was found (P < 0.05; R = 0.748). The spherical aberration (SA) increased for anterior corneal and total measurement, being statistically significant for all visits (P < 0.05). The internal SA decreased: − 0.105 ± 0.006 at baseline and − 0.196 ± 0.203 at 1 week (P < 0.05). No difference between baseline and the follow-up visits in posterior corneal SA was found (P > 0.05)ConclusionThe negative SA of the lens increases during OK treatment compensated for the increase of the anterior corneal surface positive SA, in addition to increasing the accommodative response.

Purpose The purpose of this study is to evaluate ocular, corneal, and internal aberration parameters in eyes with keratoconus (KC), forme fruste keratoconus (FFKC), and normal eyes. Method In a prospective study, one eye of 110 patients with KC, 60 FFKC patients, and 150 healthy participants was evaluated using OPD-Scan II. Ocular, corneal, and internal higher-order aberrations were measured through a sixth-order Zernike polynomial decomposition. Receiver operating characteristic analysis was performed to evaluate the diagnostic ability of the aberration parameters in discriminating KC and FFKC from normal eyes. Results The root mean square of the all ocular aberration measurements was significantly higher in the KC and FFKC patients than that of normal participants ( p  < 0.05). All of the corneal aberration measurements were significantly higher in KC patients than those of normal patients ( p  < 0.05); however, only corneal total higher-order aberration (HOA), vertical and total coma, and higher-order astigmatism were significantly higher in the FFKC patients than normal participants ( p  < 0.05). The results also showed that internal aberration lower-order astigmatism, total trefoil, and total higher-order spherical aberration were significantly different between KC and normal groups ( p  < 0.05). In comparison, internal total HOA, lower and higher-order astigmatism, total trefoil, and vertical coma were significantly different between FFKC and normal groups ( p  < 0.05). Ocular vertical and total coma had the highest ability in discriminating keratoconic from normal eyes. Ocular total higher aberration and total coma had the highest diagnostic ability in discriminating FFKC from normal eyes. The diagnostic ability of internal aberration, on the other hand, was moderate to poor in discriminating KC and FFKC from normal eyes. Conclusion Ocular aberration especially vertical and total coma and total HOA were found to be suitable parameters to discriminate KC and FFKC from normal patients. These two parameters could be used as discriminating factors in evaluating the patient for refractive surgery in an attempt to avoid iatrogenic ectasia.

The replacement of bulk refractive optical elements with diffractive planar components enables the miniaturization of optical systems. However, diffractive optics suffers from large chromatic aberrations due to the dispersion of the phase accumulated by light during propagation. We show that this limitation can be overcome with an engineered wavelength-dependent phase shift imparted by a metasurface, and we demonstrate a design that deflects three wavelengths by the same angle. A planar lens without chromatic aberrations at three wavelengths is also presented. Our designs are based on low-loss dielectric resonators, which introduce a dense spectrum of optical modes to enable dispersive phase compensation. The suppression of chromatic aberrations in metasurface-based planar photonics will find applications in lightweight collimators for displays, as well as chromatically corrected imaging systems.

The precorneal tear film is maintained by blinking and exhibits different phases in the tear cycle. The tear film serves as the most anterior surface of the eye and plays an important role as a first refractive component of the eye. Alterations in tear film dynamics may cause both vision-related and ocular surface-related symptoms. Although the optical quality associated with the tear film dynamics previously received little attention, objective measurements of optical quality using wavefront sensors have enabled us to quantify optical aberrations induced by the tear film. This has provided an objective method for assessing reduced optical quality in dry eye; thus, visual disturbances were included in the definition of dry eye disease in the 2007 Dry Eye Workshop report. In addition, sequential measurements of wavefront aberrations have provided us with valuable insights into the dynamic optical changes associated with tear film dynamics. This review will focus on the current knowledge of the mechanisms of wavefront variations that are caused by different aspects of tear film dynamics: specifically, quality, quantity and properties of the tear film, demonstrating the respective effects of dry eye, epiphora and instillation of eye drops on the quality of vision.

Purpose Compared to Shack-Hartmann wavefront sensor (SHWS), the parameters of virtual SHWS (vSHWS) can be easily adjusted to obtain the optimal performance of aberration measurement. Its current optimal parameters are obtained with only a set of statistical aberrations and not statistically significant. Whether the above parameters are consistent with the statistical results of the optimal parameters corresponding to each set of aberrations, and which performance is better if not? The purpose of this study was to answer these questions. Methods The optimal parameters to reconstruct 624 sets of clinical ocular aberrations in the highest accuracy, including the numbers of sub-apertures (NSAs) and the expansion ratios (ERs) of electric field zero-padding, were determined sequentially in this work. By using wavefront-reconstruction accuracy as an evaluation index, the statistical optimal parameter configuration was selected from some possible configurations determined by the optimal NSAs and ERs. Results The statistical optimal parameters are consistent for normal and abnormal eyes. They are different from the optimal parameters obtained with a set of statistical aberrations from the same 624 sets of aberrations, and the performance using the former is better than that using the latter. The performance using a fixed set of statistical optimal parameters is even close to that using the respective optimal parameters corresponding to each set of aberrations. Conclusion The vSHWS configured with a fixed set of statistical optimal parameters can be used for high-precision aberration measurement of both normal and abnormal eyes. The statistical optimal parameters are more suitable for vSHWS than the parameters obtained with a set of statistical aberrations. These conclusions are significant for the designs of vSHWS and also SHWS.

PURPOSE: To compare ocular and internal aberrations after femtosecond laser anterior capsulotomy and continuous curvilinear capsulorrhexis in cataract surgery. METHODS: In this prospective study, anterior capsulotomy was performed during cataract surgery with an intraocular femtosecond (FS) laser (Alcon LenSx Inc) in 48 eyes. As a control group, continuous curvilinear capsulorrhexis (CCC) was performed in 51 eyes. Wavefront aberrometry, corneal topography, and objective visual quality were measured using the OPD-Scan (NIDEK Co Ltd). Vertical and horizontal tilt, coma, and visual quality metrics were evaluated separately to determine whether the source of aberrations was ocular or internal. Main outcome measures included postoperative residual refraction, uncorrected and corrected visual acuities, ocular and internal aberrations, Strehl ratio, and modulation transfer function (MTF). RESULTS: No statistically significant differences were noted between the FS and CCC groups, respectively, in postoperative sphere (−0.60±1.50 vs −0.50±1.40 diopters [D]), postoperative cylinder (1.30±1.01 vs 1.10±1.10 D), uncorrected distance visual acuity (0.86±0.15 vs 0.88±0.08), or corrected distance visual acuity (0.97±0.08 vs 0.97±0.06). The FS group had significantly lower values of intraocular vertical tilt (−0.05±0.36 vs 0.27±0.57) and coma (−0.003±0.11 vs 0.1±0.15), and significantly higher Strehl ratios (0.02±0.02 vs 0.01±0.01) and MTF values at all measured cycles per degree, compared to the CCC group. CONCLUSIONS: Capsulotomy performed with an intraocular FS laser induced significantly less internal aberrations measured by the NIDEK OPD-Scan aberrometer compared to eyes that underwent CCC, which may result in better optical quality after the procedure.