Measurement Of Spherical Aberration Research Articles

Analog holographic wavefront sensor for defocus and spherical aberration measurement recorded in a photopolymer.

An analog holographic wavefront sensor (AHWFS), for measurement of low and high order (defocus and spherical aberration) aberration modes has been developed as volume phase holograms in a photopolymer recording medium. This is the first time that high order aberrations such as spherical aberration can be sensed using a volume hologram in a photosensitive medium. Both defocus and spherical aberration were recorded in a multi-mode version of this AHWFS. Refractive elements were used to generate a maximum and minimum phase delay of each aberration which were multiplexed as a set of volume phase holograms in an acrylamide based-photopolymer layer. The single-mode sensors showed a high degree of accuracy in determining various magnitudes of defocus and spherical aberration generated refractively. The multi-mode sensor also exhibited promising measurement characteristics and similar trends to the single-mode sensors were observed. The method of quantifying defocus was improved upon and a brief study into material shrinkage and sensor linearity is presented.

Adaptive optics via pupil ring segmentation improves spherical aberration correction for two-photon imaging of optically cleared tissues.

Optical clearing methods reduce the optical scattering of biological samples and thereby extend optical imaging penetration depth. However, refractive index mismatch between the immersion media of objectives and clearing reagents induces spherical aberration (SA), causing significant degradation of fluorescence intensity and spatial resolution. We present an adaptive optics method based on pupil ring segmentation to correct SA in optically cleared samples. Our method demonstrates superior SA correction over a modal-based adaptive optics method and restores the fluorescence intensity and resolution at high imaging depth. Moreover, the method can derive an SA correction map for the whole imaging volume based on three representative measurements. It facilitates SA correction during image acquisition without intermittent SA measurements. We applied this method in mouse brain tissues treated with different optical clearing methods. The results illustrate that the synaptic structures of neurons within 900 μm depth can be clearly resolved after SA correction.

Effects of relative negative spherical aberration in single vision contact lens visual performance.

ObjectiveThe study aimed to compare the visual performance of contact lenses with and without negative spherical aberration (SA) over 5 days of wear.MethodsAt baseline, 32 myopic participants (aged 18–33 years) were fitted in a randomized order with two lenses (test lens with minimal or no SA and 1-Day Acuvue Moist designed with negative SA) for 5 days (minimum 6 hours wear/day). Participants returned for a follow-up visit. This consisted of on-axis SA measurements; high- and low-contrast visual acuities at 6 m; high-contrast acuities at 70 and 40 cm; low-illumination, low-contrast acuity at 6 m; stereopsis at 40 cm; horizontal phorias at 3 m and 33 cm; and ±2.00 D monocular accommodative facility at 33 cm. Participants also rated (1–10 scale) vision quality (clarity and lack of ghosting for distance, intermediate, near, driving vision and vision stability during day- and night-time), overall vision satisfaction, ocular comfort, and willingness to purchase (yes/no response).Results1-Day Acuvue Moist induced significantly (p<0.05) more negative SA at distance (Δ=0.078 μm) and near (Δ=0.064 μm) compared to the test lens, for a 6 mm pupil. There were no significant differences (p>0.05) in acuity, binocular vision, and all subjective metrics except vision stability between lenses where the test lens was rated to provide more stable vision (p<0.05).ConclusionContrary to expectations, incorporating negative SA in single vision soft contact lenses did not improve visual performance in non-presbyopic adult myopes.

Measurement of corneal spherical aberration with KR-1W aberrometer in age-related cataract patients

Objective To investigate the measurement of corneal spherical aberration in cataract patients with KR-1W aberrometer. Methods The data of 200 eyes of 142 patients with age-related cataract were collected and examined. High order aberrations (HOAs) from the anterior surface of cornea were measured, which included the total high order aberration (tHOA), spherical aberration (SA), coma and trefoil. Root-mean-square (RMS) values of HOAs were obtained with KR-1W aberrometer, both at 4.0 mm and 6.0 mm pupil diameters (PD). Results At 4 mm PD, age-related cataract patients corneal tHOA, SA, coma and trefoil in turn were (0.17±0.06) μm, (0.05±0.03) μm, (0.10±0.05) μm and (0.10±0.06) μm. At 6 mm PD, the corneal tHOA, SA, coma and trefoil in turn were (0.48±0.13) μm, (0.25±0.07) μm, (0.26±0.12) μm and (0.20±0.10) μm. The range of SA with 6mm PD was from 0.06 μm to 0.54 μm. Conclusion Design of aspheric IOLs based on + 0.27 μm corneal SA is reasonable. Given on account of the wide distribution range of corneal SA, aspheric IOLs should be individually selected based on measurement of corneal SA before cataract surgery. Key words: Cataract, age-related; Aberration, high order; Aberration, spherical; Aberrometer, KR-1W

Spherical aberration measurement of a microscope objective by use of calibrated spherical particles.

The purpose of this paper is to characterize the spherical aberration of a microscope objective lens by using diffraction light from nanosphere particles. The experimental image of the diffraction spot of a nanosphere is fitted with the Nijboer-Zernike model to estimate the spherical aberration. The method can easily be extended to the measurement of other and higher-order aberrations. Noticeable features of this new measurement technique are real-time measurements, simple structure, and flexibility, which lead it to measure optical aberrations with a good accuracy.

Clinical study of customized aspherical intraocular lens implants.

To compare if there is an improvement in visual functions with age-related cataracts between patients receiving a aspherical intraocular lens (IOL) based on corneal wavefront aberration and patients randomly assigned lenses. A total of 124 eyes of 124 patients with age-related cataracts were placed in experimental group and a group receiving randomly assigned (RA) lenses. The experimental group was undergone Pentacam corneal spherical aberration measurement before surgery; the targeted range for residual total spherical aberration after surgery was set to 0-0.3 µm. Patients with a corneal spherical aberration <0.3 µm were implanted with a zero-spherical aberration advanced optics (AO) aspherical IOL and patients with an aberration ≥0.3 µm received a Tecnis Z9003 aspherical lens in experimental group. RA patients were randomly implanted with an AO lens or a Tecnis Z9003 lens. Three months after surgery total spherical aberration, photopic/mesopic contrast sensitivities, photopic/mesopic with glare contrast sensitivities, and logMAR vision were measured. Statistical analysis on logMAR vision showed no significant difference between two groups (P=0.413). The post-surgical total spherical aberration was 0.126±0.097 µm and 0.152±0.151 µm in the experimental and RA groups, respectively (P=0.12). The mesopic contrast sensitivities at spatial frequencies of 6, 12 and 18 c/d in the experimental group were significantly higher than of the RA group (P=0.00; P=0.04; P=0.02). The mesopic with glare contrast sensitivity in the experimental group at a spatial frequency of 18 c/d was also significantly higher vs the RA group (P=0.01). Pre-surgical corneal spherical aberration measurement in cataract patients followed by customized selection of aspherical IOL implants improved mesopic contrast sensitivities at high spatial frequencies, and thus is a superior strategy compared to the random selection of aspherical IOL implants.

The measurement of corneal spherical aberration in the patients with cataract and the application in the choice of aspherical intraocular lens

Objective To investigate the distribution of spherical aberration of anterior corneal surface in Chinese eyes with cataract and the related factors of spherical aberration for the choice of aspheric intraocular lens.Methods Spherical aberration of anterior corneal surface,asphericity Q value and average corneal curvature was measured with an iTrace wavefront analyzer in 572 Chinese patients (572 eyes) with cataract.Axial length measured by IOLMaster was recorded for each eye.To analysis the relationship between spherical aberration of anterior corneal surface and age,asphericity Q value,average corneal curvature,corneal astigmatism,axial length.Results Mean value of spherical aberration was (0.25 ± 0.08) μm for the central 6-mm zone.The spherical aberration was positively correlated with asphericity Q value,average corneal curvature and negatively correlated with axial length (P ＜ 0.05).No statistically significant correlation was found between spherical aberration and age,astigmatism(P ＞ 0.05).The influence of asphericity Q value(Beta =0.837,P ＜0.001) and average corneal curvature (Beta =0.250,P ＜0.001) were statistically significant in spherical aberration.The data were divided into three groups according to asphericity Q value(G1:-1 ＜ Q ＜ 0; G2:Q =0; G3:Q ＞ 0).The difference in spherical aberration among three groups was statistically significant (P ＜ 0.05).Conclusion There is significant interindividual variability in corneal spherical aberration.Corneal spherical aberration is correlated with asphericity Q value,average corneal curvature positively and axial length negatively.The influence of asphericity Q value and average corneal curvature are statistically significant.Accurate measurement of spherical aberration is necessary for the individualized choice of aspherical intraocular lens. Key words: Aberration, spherical; Lens, intraocular; aspherical ; Cornea

Comparing the Optical Properties of Soft Contact Lenses On and Off the Eye

The purpose of the current study was to examine the on- and off-eye optical performance of two types of soft contact lenses (hydrogel and silicone hydrogel). The monochromatic aberrations (λ = 850 nm) of contact lenses were measured on-eye using a clinical Shack-Hartmann ocular aberrometer. In addition, we used an off-eye single-pass contact lens aberrometer (λ = 540 nm) in which the soft contact lens was placed within a wet cell. Comparison of the lower and higher order aberrations measured with these two methods required compensation for different wavelengths and knowledge of the refractive index of the contact lens materials. The measured on-eye sphere and spherical aberration values were generally similar to those measured off-eye and those specified by the lens manufacturers for both types of soft contact lenses. However, there were notable differences, especially for high plus-powered lenses, which typically exhibited lower sphere power on the eye than expected from the lens specifications and from the off-eye measured powers, both of which were almost identical. Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometric optics theory. Longitudinal spherical aberration measurements on- and off-eye, however, deviated significantly from that expected of a thin lens with spherical surfaces due to surface asphericities. The difference between on- and off-eye optics can be modeled as a tear lens or as relative lens thickness changes caused by lens flexure. The results of the current study reveal that the major difference between the on-eye lens optics and the manufacturers' specifications is not due to lens errors but due to eye-lens interactions, which could be either lens flexure or a tear lens forming behind the soft contact lens.

Clinical Study of Customized Selected Aspherical Intraocular Lens Implants

Aims: To compare if there is an improvement in visual functions with age-related cataracts between patients receiving customized selected aspherical intraocular lens (IOL) implants and patients randomly assigned lenses. Methods: Ninety-four patients (94 eyes) with age-related cataracts were placed in experimental group or a group receiving randomly assigned (RA) lenses. All patients were undergone Pentacam corneal spherical aberration measurement before surgery; The targeted range for residual total spherical aberration after surgery was set to 0-0.3 μm in experimental group. Patients with a corneal spherical aberration ≤ 0.3 μm were implanted with a zero-spherical aberration advanced optics (AO) aspherical intraocular lens and patients with an aberration 0.3 μm received a Tecnis ZA9003 aspherical lens. RA patients were randomly implanted with an AO lens or a Tecnis ZA9003 lens. Three months after surgery total spherical aberration, photopic/mesopic contrast sensitivities, photopic/mesopic with glare contrast sensitivities, and LogMAR vision were measured. Results: Statistical analysis on LogMAR vision showed no significant difference between two groups (P = 0.308). The post-surgical total spherical aberration was 0.120 ± 0.097 μm and 0.158 ± 0.152 μm in the experimental and RA groups, respectively (P = 0.08). The mesopic contrast sensitivities at spatial frequencies of 6, 12 and 18 c/d in the experimental group were significantly higher than of the RA group (P = 0.00; P = 0.04; P = 0.01). The mesopic with glare contrast sensitivity in the RA group at a spatial frequency of 18 c/d was also significantly higher vs. the RA group (P = 0.02). Conclusion: Pre-surgical corneal spherical aberration measurement in cataract patients followed by customized selection of aspherical intraocular lens implants improved mesopic contrast sensitivities and mesopic with glare contrast sensitivities at high spatial frequencies, and thus is a superior strategy compared to the random selection of aspherical intraocular lens implants.

Outcomes of Corneal Spherical Aberration-Guided Cataract Surgery Measured by the OPD-Scan

To determine based on preoperative corneal spherical aberration, the practicality of targeting zero total ocular postoperative spherical aberration when selecting an aspheric intraocular lens (IOL). Consecutive cataract patients were selected to receive an aspheric IOL based on corneal spherical aberration. A target of zero postoperative total spherical aberration Z(4,0) was calculated. One of three IOLs was chosen, based on the corneal spherical aberration Z(4,0) measurement at the 6-mm optical zone. The IOL was selected based on the summation of the corneal spherical aberration and the aspheric value of the prolate optic. The intention was an absolute value of zero total spherical aberration. Statistical analysis of the postoperative total ocular wavefront profile was performed to assess the accuracy of aspheric IOL selection. Forty eyes of 40 patients were available for postoperative assessment. The Tecnis Z9003 (Abbott Medical Optics) was implanted in 25 eyes with a preoperative corneal spherical aberration of +0.311±0.054 μm, the AcrySof IQ (Alcon Laboratories Inc) in 13 eyes (+0.188±0.034 μm), and the SofPort-Advanced Optic with Violet Shield (Bausch & Lomb) was implanted in 2 eyes (+0.0915 μm). Total postoperative ocular spherical aberration for the entire group measured +0.019±0.051 μm (Tecnis: +0.024±0.058 μm; AcrySof IQ: +0.010±0.035 μm; and SofPort AOV: +0.037 μm). Mean absolute predictive error, for the entire group, measured +0.025±0.020 μm. Skiascopy-derived total wavefront measurement of spherical aberration is a reproducible method of aspheric IOL selection and permits more precise control of total ocular spherical aberration.

Measurement of corneal aberrations for customisation of intraocular lens asphericity: impact on quality of vision after micro-incision cataract surgery

AimsTo compare the quality of vision of patients with customised aspheric intraocular lenses (IOL) versus patients implanted with zero-aberration IOL after a 1.8 mm micro-incision cataract surgery (MICS).MethodsFourty-three eyes were...

Visual function after cataract surgery in patients with an aspherical lens without spherical aberration

Abstract Purpose To compare quality of vision in pseudophakic patients with customized‐asphericity intraocular lens (IOL) compared to patients with zero‐aberration IOL after a Micro‐Incision Cataract Surgery (MICS). Methods 26 patients (41 eyes) were divided into two groups: 24 eyes received a customized‐aspheric IOL in both eyes and 17 eyes received zero‐aberration IOLs. IOL asphericity was customized according to the preoperative corneal spherical aberration (SA) in order to obtain a total ocular SA close to +0 µm. We implanted either aspherical AcriSmart 36A® generating a ‐0,18 µm SA (for a 6 mm pupil diameter), or zero‐aberration AcriSmart 46LC®. Postoperative evaluations were conducted 6 months after MICS: refraction, best‐corrected visual acuity (BCVA), contrast sensitivities, point spread function (PSF), Modulation Transfer Function (MTF), objective depth‐of‐focus and ocular wavefront aberrations were analyzed. Results Postoperative BCVA was similar in both groups (‐0,021 ± 0,105 LogMAR for the custom group versus 0 ± 0,11 LogMAR, p=0,58). Mesopic contrast sensitivity was significantly better in the custom group at intermediate and high spatial frequencies (p&lt;0.001). SA was significantly lower in the custom group (Z40 = 0,085 ± 0,07 µm vs 0,261 ± 0,09 µm, p&lt;0.001) whereas no difference of preoperative corneal SA was noted. MTF cutoff frequency is lower in the reference group than in the custom group (p=0,008). The objective residual accommodative amplitude was lower in the custom group: 1,31 ± 0,54 D versus 2,25 ± 0,65 D (p=0,006). Conclusion Individual selection of IOL asphericity with a preoperative corneal spherical aberration measurement allowed control of final total amount of spherical aberration. Such a customization improved mesopic contrast sensitivity, and leads to better objective quality of vision.

The effect of altering spherical aberration on the static accommodative response

To investigate the effect of altering the spherical aberration (SA) of the eye on the static accommodative response. Participants were fitted with nominally afocal contact lenses with controlled amounts of SA of either -0.2, -0.1, 0.0, +0.1 or +0.2 microm for a 5-mm pupil. Measurements of SA and root mean square (RMS) total aberration for the eye plus lens for each participant were determined with a Complete Ophthalmic Analysis System aberrometer. Accommodation was stimulated either by placing targets at different dioptric distances from the eye, or by using a fixed distance target and placing negative-powered lenses in front of the eye. Accommodation responses were determined with a Shin-Nippon autorefractor. For both stimuli situations, the slope of the accommodation stimulus-response function was lowest for the lenses with +0.2 microm SA, and increased as the amount of SA was reduced. There was a significant negative correlation between SA and slope. Lag of accommodation at 33 cm correlated well with added SA, but did not correlate with total RMS error. There was no significant difference between the responses at 30 min after lens wear started and the responses after 1 h. Adding negative SA to the eye generally improves the slope of the accommodation stimulus-response curve and decreases lag of accommodation, and positive added SA depresses the slope of the stimulus-response curve and increases lag. The effect seems to be specific to SA, as there was no relationship between lag and RMS error. Altering SA may be a viable way of changing accommodative functions in clinical situations.

Multifocal Corneal Ablation for Hyperopic Presbyopes

To investigate the clinical results of multifocal wavefront-guided corneal ablation with a central near zone in hyperopic presbyopes. Twenty-seven patients (54 eyes) were analyzed retrospectively. Monocular near and distance uncorrected visual acuity (UCVA) and binocular near and distance UCVA were measured preoperatively, and the near addition power and the manifest refraction were obtained. Measurements of spherical aberration, coma, total higher order aberration, and contrast sensitivity for high and low photopic conditions were performed. All patients received multifocal corneal ablations with a central near zone using the VISX CustomVue System and were examined at 1 month (48 eyes), 2 months (42 eyes), and 6 months (28 eyes) after surgery. Of 14 patients, 9 (64.3%) achieved both 0.8 or better in binocular distance UCVA and 0.65 or better in binocular near UCVA, and the spherical equivalent refraction and near addition power decreased from +1.16+/-0.82 diopters (D) to +0.33+/-0.45 D and from 2.35+/-0.44 D to 1.42+/-0.62 D at 6 months after surgery, respectively. No significant changes were noted in total higher order aberration and contrast sensitivity, whereas spherical aberration coefficients (Z-12) changed from positive to negative. Multifocal wavefront-guided refractive surgery in presbyopia offered effective correction in hypermetropia and satisfactory near vision without significant increase in comeal total higher order aberration or significant decrease in contrast sensitivity.

Lithographic characterization of the spherical error in an extreme-ultraviolet optic by use of a programmable pupil-fill illuminator

Extreme-ultraviolet (EUV) lithography remains a leading contender for use in the mass production of nanoelectronics at the 32 nm node. Great progress has been made in all areas of EUV lithography, including the crucial issue of fabrication of diffraction-limited optics. To gain an accurate understanding of the projection optic wavefront error in a completed lithography tool requires lithography-based aberration measurements; however, making such measurements in EUV systems can be challenging. We describe the quantitative lithographic measurement of spherical aberration in a 0.3 numerical aperture. EUV microfield optic. The measurement method is based on use of the unique properties of a programmable coherence illuminator. The results show the optic to have 1 nm rms spherical error, whereas interferometric measurements performed during the alignment of the optic indicated a spherical error of less than 0.1 nm rms.

Relationship between Refractive Error and Monochromatic Aberrations of the Eye

To examine the relationship between ametropia and optical aberrations in a population of 200 normal human eyes with refractive errors spanning the range from +5.00 to -10.00 D. Using a reduced-eye model of ametropia, we tested the hypothesis that the optical system of the eye is uncorrelated with the degree of ametropia. These predictions were evaluated experimentally with a Shack-Hartmann aberrometer that measured the monochromatic aberrations across the central 6 mm of the dilated pupil in well-corrected, cyclopleged eyes. Optical theory predicted, and control experiments on a model eye verified, that Shack-Hartmann measurements of spherical aberration will vary with axial elongation of the eye even if the dioptric components of the eye are fixed. Contrary to these predictions, spherical aberration was not significantly different from emmetropic eyes. Root mean square of third-order aberrations, fourth-order aberrations, and total higher aberrations (third to 10th) in myopic and hyperopic eyes were also uncorrelated with refractive error. Astigmatic eyes tended to have larger total higher-order aberrations than nonastigmatic eyes. We conclude that a reduced-eye model of myopia assuming fixed optical parameters and variable axial length is not tenable.

Measurement of Spherical Aberration Utilizing an Alternating Phase Shift Mask

A spherical aberration function is measured utilizing an alternating phase shift mask (PSM). First, it is theoretically considered that with a highly coherent illumination, the focus of the alternating phase shift lines and spaces (L/S) pattern is equivalent to that of rays in a small annular area of the reference sphere when the aberration function is axially symmetric in the sphere. Then, the focus variation with the pattern pitch is obtained by a printing experiment that employs an alternating PSM. After a primitive mathematical operation, the aberration function is obtained from the experimentally observed focus variation. The aberration function is examined by investigating various anomalous phenomena observed in the printing with the various resolution enhancement techniques (RETs). The comparison between the experimentally observed phenomena and the predictions based on the calculated images with the measured aberration functions shows fair agreement. Consequently, the validity of this measurement method is confirmed.

Measurement of spherical aberration in STEM

The spherical aberration coefficients, C s, of two objective lens pole pieces of a VG HB501A scanning transmission electron microscope (STEM) have been measured using power spectrum analysis of bright-field (BF) images of amorphous carbon films recorded at 100 keV. The high-resolution pole piece and the analytical pole piece have measured values of C s = 1.29 ± 0.23 mm, respectively. A small BF detector of 0.6 mrad allows coherent imaging, and a long dwell time attains a high signal-to-noise ratio. The imaging parameters have been measured with an accuracy comparable to that obtained in TEM.

Retinal illuminance using a wide-angle model of the eye.

A computer model of relative retinal illuminance, based on our optical wide-angle model of the eye, is proposed for the cases of Ganzfeld illumination and the Maxwellian view through a range of visual field angles from 0 degrees to 80 degrees. The proposed model is designed to be functionally correct and to represent closely the anatomical parameters of the eye. Unlike earlier proposed models, this model is based on our previously reported measurements of spherical aberration in 100 eyes in vivo and is designed to be correct in the peripheral field and with large pupils. Data are reported for pupil diameters of 2, 4, and 8 mm. The effect of crystalline lens extinction on retinal illumination is also estimated for average eyes of young (age 19 years) and old (age 63 years) individuals at two wavelengths (410 and 532 nm). In the Ganzfeld case, illumination of the retina decreases with increasing visual angle. In the Maxwellian view, retinal illuminance increases with increasing visual angle.

Measurement of axial geometrical aberrations of the probe-forming lens by means of the shadow image of fine particles

A method using a shadow image of fine particles, proposed for the stigmation and the measurement of spherical aberration of the probe-forming lens, was further developed for the accurate measurement of spherical aberration and of non-rotationally symmetrical axial aberrations. From the radii of the rings of infinite magnification in a pair of shadow images, the coefficient of two- or three-fold astigmatism or axial coma can be measured together with the spherical aberration coefficient. A theoretical evaluation and an experiment carried out with a probe-forming lens of 1.5 nm resolution showed that the error of measurement is within several percent for the spherical aberration coefficient and is less than 30 nm for the coefficient of two-fold astigmatism. The three-fold astigmatism remaining after the correction of spherical aberration was also measured and was found to be of considerable importance in limiting the performance of the spherically corrected lens.