Coma Aberration Research Articles

Highly-chirped Bragg gratings for integrated silica spectrometers.

A blazed chirped Bragg grating in a planar silica waveguide device was used to create an integrated diffractive element for a spectrometer. The grating diffracts light from a waveguide and creates a wavelength dependent focus in a manner similar to a bulk diffraction grating spectrometer. An external imaging system is used to analyse the light, later device iterations plan to integrate detectors to make a fully integrated spectrometer. Devices were fabricated with grating period chirp rates in excess of 100 nm mm-1, achieving a focal length of 5.5 mm. Correction of coma aberrations resulted in a device with a footprint of 20 mm×10 mm, a peak FWHM resolution of 1.8 nm, a typical FWHM resolution of 2.6 nm and operating with a 160 nm bandwidth centered at 1550 nm.

Short and long term outcomes after small-incision lenticule extraction: A tertiary referral centre experience

The objective of this study is to evaluate the preoperative and short- and long-term postoperative results in terms of visual acuity, refractive error, and corneal wavefront aberrations in patients with myopia and myopic astigmatism undergoing small incision lenticule extraction (SMILE). Seventy-nine eyes of 52 myopes with or without astigmatism (41 right and 38 left) were enrolled in this retrospective study. The measurements included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE) and wavefront aberrations. All the measurements before and after SMILE surgery were systematically recorded. Mean preoperative UDVA was 1.19±0.24 logMAR and improved to 0.06±0.17 logMAR at the 3-year postoperative follow-up. At the conclusion of the 3-year follow-up, UDVA was better than or equal to 20/20 and 20/25 in 73% and 84% of eyes, respectively. At 1 month postoperatively, CDVA was 0.05±0.23 logMAR and significantly lower than the preoperative CDVA, 0.02±0.04 log MAR (P>0.05). However, at 1 year and 3 years after surgery, CDVA showed a significant increase compared to preoperative CDVA. At the conclusion of the 3-year follow-up, SE was -0.47 D, and 69.6% and 83.5% of the eyes were within±0.50 D and±1.00 D, respectively, of the intended correction. HOA's, coma, and spherical aberration increased significantly. No significant change in trefoil was detected. This study showed that SMILE produces a stable, safe outcome for surgical treatment of myopia and myopic astigmatism.

Comparative Analysis on Refractive Errors and High-Order Aberrations according to Changes in Pupil Size before and after Presbyopia

Purpose : The purpose of this study was provide information that could be helpful in clinical practice for, presbyopia prescription as, classifying and analyzing refractive errors and highorder aberrations according to changes in pupil size into age groups before and after presbyopia. Methods : Refractive errors and high-order aberrations were measured between 20~80 years of age adults males and females who had no eyes disease and refractive surgery, and they were divided into two groups such as, 20~40 years and 45~80 years. A paired-T test was used to compare refractive errors and high-order aberrations according to the changes in pupil size, and correlation analysis according to age was conducted by Pearson correlation. Results : The spherical equivalent power of 20~40 years was –3.193±2.494 D at 3 mm of pupil size, and the spherical equivalent power at 5 mm was –3.386±2.451 D, showing that myopia of 0.193 D increased. The spherical equivalent power of 45~80 years was 0.015±1.340 D at 3 mm of pupil size, and the spherical equivalent power at 5 mm was –0.054±1.566 D, showing that myopia of 0.069 D increased. In addition, at a pupil size of 3 mm, coma aberration of 0.026 μm, spherical aberration of 0.016 μm, trefoil aberration of 0.037 μm, astigmatism of 0.012 μm, and quatrefoil aberration of 0.022 μm was increased in 45~80 years more than those 20~40 years. Conclusion : When prescribing progressive lenses for presbyopia correction, it is considered to be prescribed with reference to pupil size or high-order aberrations that can degrade vision.

Zernike coefficients from wavefront curvature data.

The concept of curvature sensing is reviewed, and a comprehensive derivation of the curvature polynomials is given, whose inner products with the wavefront curvature data yield the Zernike aberration coefficients of an aberrated circular wavefront. The data consist of the Laplacian of the wavefront across its interior and its outward normal slope at its circular boundary. However, we show that the radial part of the curvature polynomials and their slopes at the boundary of the wavefront have a value of zero, except when the angular frequency of the corresponding Zernike polynomial is equal to its radial degree. As a result, the effect of noise on the corresponding Zernike coefficients is lower because the noisy data at the boundary of the wavefront is not used to determine their values. The use of the curvature polynomials to determine the Zernike coefficients is demonstrated with simulated noisy curvature data of an aberration function consisting of 10 Zernike coefficients, namely defocus, primary, secondary, and tertiary astigmatism, coma, and spherical aberrations.

The Effect of adding First Order Aberrations To Third Order Aberrations on Point Spread Function for Triangular Aperture

In this work, Point Spread Function (PSF) for triangular aperture was studied, in case of ideal optical system, also in case of presence first order aberrations )focal error and tilt aberration) and third order aberrations (spherical ,coma, and astigmatism aberrations) individually, and for the same values of aberration factor )W=0.1λ …..0.5 λ ) for angle of rotation (ѱ =0). First order aberrations were added to third order aberrations, to obtain the best balance and to reduce the curve width of the (PSF), and to increase the Strehl ratio, like adding a tilt aberration to the coma aberration and adding focal error to spherical aberration and astigmatism aberration. There are some aberrations effects impact negatively on point spread function, such as focal error with coma aberration and tilt aberration with spherical aberration.

Customized Wavefront-Optimized Transepithelial Photorefractive Keratectomy for a Retained Lenticule Fragment After Primary SMILE.

To describe the surgical outcomes after transepithelial photorefractive keratectomy (PRK) for a case of retained intrastromal lenticule fragment after small incision lenticule extraction (SMILE). Transepithelial PRK was performed to minimize corneal irregularity and to correct residual refractive errors in a patient who had undergone failed lenticule extraction, which resulted in a refractive lenticule fragment being retained for 14 months after primary SMILE. At the postoperative 6-month visit, uncorrected distance visual acuity and corrected distance visual acuity improved to 20/20 and 20/20, respectively, and corneal tomography depicted normalization of the corneal surface. Corneal higher order aberrations, including coma, trefoil, and spherical aberration, were markedly reduced. Transepithelial PRK is a potential option for the management of a retained lenticule fragment after primary SMILE. [J Refract Surg. 2020;36(6):395-399.].

Scleral lens wear following penetrating keratoplasty: changes in corneal curvature and optics.

Visual rehabilitation following penetrating keratoplasty is the primary indication for approximately 15% of all scleral lens fittings. Since corneal biomechanics are altered following penetrating keratoplasty, the aim of this study was to quantify changes in anterior corneal optics following short-term scleral lens wear in eyes with corneal grafts. Scheimpflug images were obtained before and after a period of scleral lens wear (mean 6.3±1.4h), from eyes that had previously undergone penetrating keratoplasty (10 eyes of nine participants, mean age 31±9years). Corneal power and thickness data were examined over the central 6mm, including regional analyses of the central (0-3mm) and the mid-peripheral cornea (3-6mm annulus) using customised software to deterime corneal power vectors M (best fit sphere), J0 (90/180 astigmatism) and J45 (45/135 astigmatism). Anterior corneal aberrations were extracted using corneal elevation data. Corneal power vector J45 increased following lens wear (by 0.22±0.05 D, p=0.003) across the central 6mm, while M displayed regional variations following lens wear indicating larger changes further from the corneal centre (p=0.004). The change in corneal power vector M was also correlated with the magnitude of central corneal swelling (r=0.65, p=0.04). The anterior corneal aberration terms of oblique astigmatism, hoirzontal coma, and spherical aberration also varied following lens wear (all p≤0.01). The mean change in the corneal spherocylinder derived from the elevation data following lens wear was +0.14/-0.54×44 for a 6mm corneal diameter. Clinically significant alterations in anterior corneal topography and higher order aberrations were observed following short-term scleral lens wear in eyes that had undergone penetrating keratoplasty. Spherocylindrical changes were approximately double the magnitude and more oblique in orientation compared to previous reports of healthy eyes. Changes in corneal power vector M may be related to epithelial corneal oedema.

Theoretical Analysis of Wave-Front Aberrations Induced from Conventional Laser Refractive Surgery in a Biomechanical Finite Element Model.

PurposeTo examine the biomechanical effects-induced wave-front aberrations after conventional laser refractive surgery.MethodsA finite element model of the human eye was established to simulate conventional laser refractive surgery with corrected refraction from –1 to –15 diopters (D). The deformation of the anterior and posterior corneal surfaces was obtained under the intraocular pressure (IOP). Then, the surface displacement was converted to wave-front aberrations.ResultsFollowing conventional refractive surgery, significant deformation of the anterior and posterior corneal surfaces occurred because of the corneal biomechanical effects, resulting in increased residual wave-front aberrations. Deformation of the anterior surface resulted in a hyperopic shift, which was significantly increased with the increasing refractive correction. The residual high-order aberrations consisted of spherical aberration, vertical coma, and y-trefoil. Spherical aberration was significantly positively correlated to enhanced refraction correction. The effect of posterior corneal surface on induced wave-front aberration was less than the anterior corneal surface. The IOP slightly affects the postoperative defocus, coma, and spherical aberration. When treatment decentration occurred during the procedure, the hyperopic shift decreased as the eccentricity increased. Treatment decentration had a significant impact on the spherical aberration and the coma. In addition, the ocular tissue elasticity played a key role in hyperopic shift, whereas it had little effect on the other aberrations.ConclusionsAmong the many factors that affect high-order aberrations after conventional laser refractive surgery, the alterations in corneal morphology caused by biomechanical effects must be considered, as they can lead to an increase in postoperative residual wave-front aberrations.

Comparison of objective and subjective visual quality early after implantable collamer lens V4c (ICL V4c) and small incision lenticule extraction (SMILE) for high myopia correction

To investigate differences in the objective and subjective visual quality of patients with high myopia following implantable collamer lens V4c (ICL V4c) versus small incision lenticule extraction (SMILE) early postoperatively. This prospective analysis included 94 eyes of 57 patients (8 males) in the ICL V4c group (mean spherical equivalent (SE), -8.07±1.03 dioptres (D)) and 103 eyes of 57 patients (13 males) in the SMILE group (mean SE, -7.85±0.78 D). Refractive parameters and wavefront aberrations were recorded preoperatively and 6months postoperatively. Subjective visual quality was scored with the Quality of Vision questionnaire, and operation satisfaction was evaluated 6months postoperatively. At 6months postoperatively, the efficacy index was 1.17±0.16 in the ICL and 1.09±0.20 in the SMILE group; the safety index was 1.21±0.18 in the ICL and 1.12±0.16 in the SMILE group. A significant increase in total higher-order aberrations (HOAs) in both the ICL and SMILE groups was observed, but to a lesser degree in ICL (p<0.05). In the ICL group, trefoil significantly increased (p<0.05), whereas in the SMILE group, coma, trefoil and spherical aberration significantly increased (p<0.05). Glare, haloes and blurred vision had the highest incidences after both types of surgery, and postoperative haloes were significantly more common following ICL; 96.1% of ICL-treated and 94.9% of SMILE-treated patients were satisfied with their visual outcomes. ICL V4c caused lower HOAs induction than SMILE. Despite the postoperative visual disturbances, both ICL and SMILE provided good efficacy, safety, predictability and high satisfaction in correcting high myopia.

Integrating optical design with Taguchi method in a remote wireless light charging system

Power cannot be efficiently transmitted over long distances using conventional wireless transmission. Although increasing charger power effectively improves charging efficiency, safety concerns include mobile phone heating, long-term health damage caused by electromagnetic waves, and interferences on other precise instruments. This study proposed a remote wireless charging system that utilizes mechanical movement design in zoom lenses to maintain wireless charging system performance and perform charging operations from different positions in a room through the movement between lens groups. Moreover, the Taguchi method was applied in optical design software to identify the optimal factors for performance improvement. The wireless light charging system was optimized using the Taguchi method. In addition, optimization of curvature, thickness, and material were proposed. Three focal lengths were optimized through 18 sets of experimental data to reduce the spherical and comatic aberrations; and modulation transfer function value was improved to enhance the performance of the remote wireless light charging system. The remote wireless light charging system was designed to be used in an indoor space. In general, the system is installed on the ceiling, and mechanical movement function is enabled for the lens. Moving the lens changes the focus of the system. This allows the charging light source to change its original light path and generate a new focal point. The system features three zoom positions: 3 m from the ceiling to the floor, 2 m from the ceiling to the desktop, and 1.5 m from the ceiling to a person standing with a mobile phone. This allows the wireless light charging system to focus on the mobile phone receiver for charging in every corner within the indoor space. The wireless charging system features three focal lengths; the field of view (FOV) values are 0°, 24°, and 34°; the total length of the system is 635.45 mm; and the size of the spot diagram is 20% at various FOV angles at a spatial frequency of 80 lp/mm; and the lateral color was < ± 2 μm. A photodiode with an area of 12.0 mm was used as the receiver, and energy could be effectively received when the spot size was greater than or equal to the receiving area.

Comparative Analysis of Visual Performance and Optical Quality with a Rotationally Asymmetric Multifocal Intraocular Lens and an Apodized Diffractive Multifocal Intraocular Lens.

Purpose To compare the short-term visual outcomes and intraocular optical performance of a rotationally asymmetric multifocal intraocular lens (MIOL) (SBL-3, Lenstec, Inc., Christ Church, Barbados) and an apodized diffractive MIOL (the Acrysof IQ ResTOR SN6AD1, Alcon Laboratories, Inc., Fort Worth, Texas, United States). Methods A prospective, comparative, nonrandomized, and single-center study. Sixty-eight age-related cataract patients (81 eyes) after phacoemulsification cataract surgery and in-the-bag MIOL implantation were enrolled. Thirty-eight eyes received SBL-3, and 43 eyes received SN6AD1. Ophthalmological evaluation included uncorrected distance visual acuity (UDVA), uncorrected intermediate visual acuity (UIVA), uncorrected near visual acuity (UNVA), corrected distance visual acuity (CDVA), modulation transfer function (MTF), Strehl ratio (SR), intraocular aberrations (4 mm optical zone), and defocus curve at 3 months postoperatively. The Chinese version of the visual function index-14 (VF-12-CN) and spectacle independence were assessed in all patients. Results There was no statistically significant difference between groups in postoperative UDVA (p = 0.186). Postoperative UIVA and UNVA were significantly better for the SBL-3 group than for the SN6AD1 group (p < 0.01). Statistically significant differences were revealed in defocus levels from –3.50 D to −4.00 D with better visual acuities for the SBL-3 group (p < 0.01). For intraocular optical quality outcomes, statistically significant differences between groups were observed in RMS of intraocular total aberrations, coma, and trefoil high-order aberrations, presenting significantly higher values of these parameters in the eyes of the SBL-3 group (p < 0.01). Statistically significant differences were revealed in the MTF values at spatial frequencies of 5 and 10 cycles/degree between groups. There were no significant differences in scores of VF-12-CN, and spectacle independence between the groups (p > 0.05). Conclusions Both MIOLs were able to successfully restore visual function after cataract surgery. SBL-3 provided better UIVA and UNVA with a wider range of intermediate vision.

The Influence of Decentration on Higher-Order Aberrations in Artisan Aphakic Intraocular Lens Implantation Eyes.

Purpose To characterize the influence of decentration on higher-order aberrations of Artisan aphakic intraocular lens implantation eyes. Setting. Department of Ophthalmology and Vision Science, Eye and ENT Hospital of Fudan University, Shanghai, China. Design Retrospective case series. Methods Twenty-three eyes of 18 patients were retrospectively examined. Location of the IOL was imaged using a slit-lamp, and decentration (the distance from the center of a pupil to the geometric center of the IOL) was measured using the AutoCAD 2007 software. Ocular and internal higher-order aberrations were measured using the wavefront analyzer KR-1W (Topcon) and their correlation with decentration were analyzed. Coma, spherical, 3rd-, 4th-order, trefoil, tetrafoil aberrations, ocular, and internal higher-order aberrations were calculated for a 4.0 mm pupil diameter. Results The mean age of patients was 33.6 ± 21.4 years (ranging from 7 to 72 years). The mean follow-up period was 28.2 ± 10.5 months (ranging from 12 to 52 months). The mean postoperative best-corrected visual acuity (BCVA) was 0.19 ± 0.19 logMAR (range −0.18–0.52). The mean decentration was 0.57 ± 0.28 mm (range 0.15–1.21 mm). There was no correlation between Artisan IOL decentration and ocular higher-order aberrations, internal higher-order aberrations, coma, spherical, 3rd-, 4th-order, trefoil, and tetrafoil aberrations, respectively. There was a positive correlation between Artisan IOL decentration and 2nd-astig aberrations when 2nd-astig aberrations were less than 0.1. Conclusions The position of Artisan IOLs showed slight decentration and the amounts of decentration were not large enough to influence higher-order aberrations.

Decentration and tilt of plate-haptic multifocal intraocular lenses in myopic eyes

BackgroundTo investigate the decentration and tilt of plate-haptic multifocal intraocular lenses (MfIOLs) in myopic eyes.MethodsMyopic (axial length [AXL] > 24.5 mm) and non-myopic (21.0 mm < AXL ≤ 24.5 mm) cataract eyes were enrolled in this prospective study and randomly assigned to receive implantation of Zeiss AT LISA tri 839MP lenses (Group A) or Tecnis ZMB00 lenses (Group B). In total, 122 eyes of 122 patients were available for analysis. Decentration and tilt of MfIOLs, high-order aberrations (HOAs), and modulation transfer functions (MTFs) were evaluated using the OPD-Scan III aberrometer 3 months postoperatively. Subjective symptoms were assessed with a Quality of Vision questionnaire.ResultsNear and distance visual acuities, tilt and horizontal decentration did not differ between the two groups, postoperatively. However, myopic eyes of Group B showed greater vertical decentration than those of Group A (− 0.17 ± 0.14 mm vs. -0.03 ± 0.09 mm, respectively), particularly when the MfIOLs were placed horizontally or obliquely. Overall decentration of myopic eyes was greater in Group B than in Group A (0.41 ± 0.15 mm vs. 0.16 ± 0.10 mm, respectively). In Group B, AXL was negatively correlated with vertical decentration and positively correlated with overall decentration. No such correlations were found in Group A. Intraocular total HOAs, coma, trefoil and spherical aberrations were lower in Group A than in Group B for a 6.0 mm pupil among myopic eyes. Generally, Group A had better MTFs and fewer subjective symptoms than Group B among myopic eyes.ConclusionsPlate-haptic design of MfIOLs may be a suggested option for myopic cataract eyes due to the less inferior decentration and better visual quality postoperatively.

Wide-field optical design for a 60 m submillimeter telescope.

We present a practical wide-field optical design for a 60 m aperture submillimeter telescope, which is currently under conceptual design study in China. The telescope is specified to operate over a wavelength range of 0.65-3 mm and provide a wide field of view (FOV) of 1° in diameter. We designed an F/6 Ritchey Chrétien (RC) system with a quasi-planar tertiary corrector, which cancels all spherical, coma, and astigmatism aberrations. It also achieves a good balance among the mirror sizes, central obscuration, and focal-plane curvature. The problems of focal surface curvature and nontelecentricity are treated in the subfield instrumental design, which employs a simple silicon wedge prism to obtain flat and telecentric focal planes for each subfield instrument module. Our studies show that by such a design, more than ${{10}^5}$105 detector pixels can be efficiently and uniformly fed at the shortest wavelength band with Strehl ratios above 0.85 across the entire 1° FOV. Several practical issues related to the telescope optics are also discussed.

Comparison of the Distribution of Lenticule Decentration Following SMILE by Pupil Center or Tear Film Mark Centration.

To investigate lenticule decentration following small incision lenticule extraction (SMILE) via the pupil center or tear film mark centration method and compare induction of corneal higher order aberrations (HOAs) between the two methods. This study analyzed decentration values obtained from tangential topography difference maps of 100 eyes (100 patients) undergoing SMILE with the pupil center (n = 50) or tear film mark (n = 50) centration method. Total HOAs and component aberrations were measured preoperatively and 6 months postoperatively. Relationships between the magnitudes of decentration and induced corneal HOAs were assessed. Both vertical and total decentered displacement were significantly different (P < .001) between the two centration groups. A significant relationship between the preoperative pupillary offset and decentration was noted in the pupil center group (P < .001), but not in the tear film mark group (P = .530). Significantly greater induction of total HOAs, coma, and vertical coma (all P < .001), as well as horizontal coma (P = .001) and spherical aberration (P = .023), were observed in the pupil center group. Association between the total decentered displacement and induced total HOAs (P < .001), as well as all other significantly increased phenomena, was also significant in the pupil center group. Differences in decentered displacement and induced corneal HOAs were significant for preoperative pupillary offset (angle kappa) greater than 200 µm, but not for angle kappa less than 200 µm. SMILE with tear film mark centration can yield improved treatment centration and less induction of total HOAs, coma, and spherical aberrations. [J Refract Surg. 2020;36(4):239-246.].

Phase modulators with tunability in wavefronts and optical axes originating from anisotropic molecular tilts under symmetric electric field II: experiments.

We demonstrate, for the first time, an electrically-tunable and physically-planar freeform optical element made up of nematic liquid crystals (LCs). Continued on numerical study in previous paper (Part I), experimental results here show that it is possible to break the rotational symmetry of the wavefront through the use of uneven tilt angles of the LC molecules even though the electric potential is rotationally symmetric. Our optical element offers the ability to electrically tune the direction of the optical axis, the wavefront deviation, as well as the Zernike polynomials for general descriptions of wavefronts. Corresponding Zernike coefficients of a Zernike polynomial that are related to defocus and spherical aberration, which can be adjusted individually or together. The minimum wavefront deviation is >λ/6. The Zernike coefficients related to coma aberration or the tilt of the optical axis are also electrically tunable. By incorporating our LC phase modulator with tunability of freeform wavefronts into a simple reflective optical system, we demonstrate convincing image performance for off-axis image aberration correction. This approach will inspire further development and design of LC optical elements for applications, such as hyperspectral imagers in aerospace optics, augmented reality, virtual reality, quantum information systems, innovative miniaturized reflective telescopic systems for astrophysics, planetary science, and earth science.

Influence of coma and spherical aberration on transmission characteristics of vortex beams in slant atmospheric turbulence

Vortex beam has potential applications in free space optical communication because of its capacity of data transmission. Therefore, it is necessary to study the propagation characteristics of vortex beams in atmospheric turbulence. When the vortex beam propagates in the atmospheric turbulence the beam drift will occur, which has a great influence on the free space optical communication. In this paper, the beam drift of vortex beams with coma and spherical aberration transmitted in atmospheric turbulence is studied by using multi-phase screen and Fourier transform method. The numerical results show that as the transmission distance increases, the effects of both coma and spherical aberration on the beam drift are enhanced. The larger the transmission zenith angle and the coma coefficients, the greater the beam drift of the vortex beam is. However, the beam drift decreases with spherical aberration coefficient increasing. When the zenith angle and the transmission distance are both unchanged, the beam drift of the both vortex beams decrease with topological charges increasing. The influence of coma aberration on beam drift is bigger than that of spherical aberration.

The influence of orthokeratology compression factor on ocular higher‐order aberrations

BackgroundTo investigate the influence of compression factor upon changes in ocular higher‐order aberrations (HOAs) in young myopic children undergoing orthokeratology treatment.MethodsSubjects aged between six and < 11-years, with low myopia (0.50–4.00 D inclusive), low astigmatism (≤ 1.25 D), and anisometropia (≤ 1.00 D), were randomly assigned to wear orthokeratology lenses of different compression factors in each eye (one eye 0.75 D and the fellow eye 1.75 D). HOAs were measured weekly over one month of lens wear. Wavefront analysis was conducted over a 5‐mm pupil using a sixth order Zernike polynomial expansion. Linear mixed models were used to examine the individual Zernike co‐efficients and specific root‐mean‐square (RMS) error (spherical, comatic, total HOAs) metrics and their changes between the two eyes during the study period.ResultsTwenty‐eight myopic (mean manifest spherical equivalent refraction: −2.10 ± 0.58 D) children (median [range] age: 9.3 [7.8–11.0] years) were analysed. Significant interocular differences in HOAs at baseline were observed for Z6−6 and Z6−4 only (both p < 0.05). During the lens wear period, eyes fitted with the increased compression factor showed greater changes in primary spherical aberration (Z40, p = 0.04) and RMS values for spherical and total HOAs (both p < 0.01). Considering data from both eyes together, after adjusting for the paired nature of the data, some other Zernike terms (Z31 and Z60, both p < 0.01) and the RMS value of comatic aberrations (p < 0.001) significantly increased after one month of orthokeratology treatment. The increase in primary spherical aberration (Z40) was positively correlated with the reduction in spherical equivalent refractive error, but only in eyes fitted with the increased compression factor (r = 0.69, p < 0.001).ConclusionsIncreasing the orthokeratology compression factor by 1.00 D significantly altered some HOAs, particularly spherical aberration. Given the association between positive spherical aberration and eye growth in children, further research investigating the influence of orthokeratology compression factor on axial eye growth is warranted.

Wavefront properties of the anterior and posterior corneal surface after transepithelial photorefractive keratectomy in myopia.

The present study aimed to evaluate the changes of corneal higher-order aberrations (HOAs) after transepithelial photorefractive keratectomy (TransPRK) in patients with myopia. A total of 80 eyes of 80 patients with myopia with or without astigmatism were evaluated. Prior to and 1 year after the surgery, uncorrected and corrected distance visual acuity in logMAR were assessed. Wavefront aberrations on the anterior surface of the cornea, as well as the posterior and total cornea, were measured via Pentacam. The HOA of the anterior surface and total values of spherical and coma aberrations increased significantly (P<0.001). However, HOAs of the anterior surface, and posterior and total values of the trefoil were not significantly changed (P=0.442, 0.805 and 0.936, respectively). A significant correlation of the pre-operative mean spherical equivalent refraction (MSER), astigmatism and central corneal ablation depth (CCAD) with the changes in coma aberration (r=0.268, P=0.016; r=0.260, P=0.020; r=0.323, P=0.004, respectively) and HOA (r=0.554, P<0.001; r=0.312, P=0.005; r=0.583, P<0.001, respectively) of the anterior surface of the cornea was determined. Furthermore, a significant correlation of the pre-operative MSER and CCAD with the changes in spherical aberration of the anterior corneal surface (r=0.462, P<0.001; r=0.510, P<0.001, respectively) was obtained. In conclusion, TransPRK offers an effective option for improving visual function in patients with myopia. The anterior corneal HOA, as well as spherical and coma aberrations, were significantly increased post-operatively. The HOA of the posterior cornea was not significantly changed. The change in the trefoil aberration was significantly correlated with pre-operative astigmatism, but the pre- and post-operative values were not significantly different.

Higher order aberrations during accommodation in children

Background: In adults, higher order aberrations (HOAs) vary during accommodation [1] which reduces retinal image quality [2]. These changes may provide a mechanism linking near work and myopia development [3], however little is known about HOAs during accommodation in children. Methodology: HOAs of 90 children (mean age and spherical equivalent refraction: 8.2 ± 1.8 years; +0.63 ± 0.34 D) were measured at four accommodation demands (0, 3, 6 and 9 D) using a Hartmann-Shack aberrometer (COAS-HD). Individual Zernike term coefficients up to and including the 6th-order were analysed over a 4 mm pupil at each accommodation demand. Root mean square (RMS) errors were calculated for total (2nd-6th orders), higher order (3rd-6th orders) (HO), individual radial orders, coma (Z[3,-1], Z[3,1], Z[5,-1] and Z[5,1]), trefoil (Z[3,-3], Z[3,3], Z[5,-3] and Z[5,3]) and spherical aberration (Z[4,0] and Z[6,0]) (SA). Visual Strehl ratios based on the optical transfer function were determined from HOAs (VSOTF). Results: Total, HO, all individual orders, coma, trefoil, and SA RMS varied significantly with accommodation demand (p Conclusions: HOAs changed significantly during accommodation resulting in a significant reduction in retinal image quality at the 9 D accommodation demand. Longitudinal studies are required to examine the potential influence of these changes on eye growth.