Differences In Spherical Aberration Research Articles

Optical Performance of a Monofocal Intraocular Lens Designed to Extend Depth of Focus.

To test the performance of a new monofocal intraocular lens, intended to extend depth of focus (Tecnis Eyhance, ICB00; Johnson & Johnson Vision, Inc) (ICB-IOL), in comparison to a standard monofocal IOL (Tecnis 1-piece, ZCB00; Johnson & Johnson Vision, Inc) (ZCB-IOL) of the same platform and material. Assessment of the optical performance of the two IOLs was made in vitro using an optical test bench with a model eye. The spherical aberration, modulation transfer function (MTF), and area under the MTF (MTFa) were obtained for pupil sizes ranging from 2 to 5 mm. Through-focus MTFa curves between -3.00 and +1.00 diopters (D) were obtained with three pupil sizes (2, 3, and 4.5 mm). Halo formation was also assessed for both lenses. The ICB-IOL had slightly worse optical quality at its best focus (ie, lower MTF scores at distance vision) and more negative spherical aberration than the ZCB-IOL for pupils ranging from 2 to 3 mm. The maximum of the through-focus MTFa curve of the ICB-IOL with a 2-mm pupil shifted to a myopic defocus of -0.50 D. For larger pupils (≥ 3.5 mm), there were no differences in spherical aberration, MTF scores, and halo energy between the two lenses. The new ICB-IOL is a modified monofocal lens with 0.50 D of additional power in its central 2-mm zone and more negative spherical aberration values, which induce a myopic shift of the maximum of optical quality and could improve intermediate vision. For pupils larger than 3.5 mm, there were no differences between IOLs. The new ICB-IOL design would produce photic phenomena comparable to a standard IOL. [J Refract Surg. 2020;36(9):625-632.].

Peripheral Monochromatic Aberrations in Young Adult Caucasian and East Asian Eyes.

Myopia prevalence rates differ between racial groups. If the growth of the eye is sensitive to differences in optical input, the difference in spherical aberration between East Asian and Caucasian eyes found in this study may be important in understanding myopia development. The aim of this study was to determine differences in peripheral wavefront aberrations between two racial groups. Wavefront aberrations were measured using a COAS-HD aberrometer across the 42 × 32° central visual field on 37 right eyes of young adults (18 Caucasians, 19 East Asians; mean age 21.5 ± 2.4 years). The mean spherical equivalent refraction was -1.94 ± 1.63 diopters (D) with a range of -5.87 to +0.16 D. Effect of race and visual field position on refractions, individual Zernike aberration coefficients up to the fourth order, higher-order root-mean-square aberration, and total root-mean-square aberration were assessed by repeated-measures analysis of covariance. Caucasians and East Asians had similar relative peripheral myopia across the visual field. All higher-order aberration coefficients were affected by visual field position. Race had no significant effect on any higher-order Zernike coefficient, but the difference in mean vertical coma coefficient (Equation is included in full-text article.)across the visual field (i.e., average of 38 field locations) approached significance, being less positive in Caucasians than in East Asians (P = .08). When correction was made for the Caucasian group being slightly less myopic than the East Asian group, spherical aberration coefficient (Equation is included in full-text article.)was less positive in Caucasians than in East Asians by 0.04 μm (P = .001). The rates of change of coma coefficients across the field were not affected by race. Caucasians and East Asians had similar relative peripheral myopia, but with less positive spherical aberration coefficient in Caucasians than in East Asians. It remains to be determined whether aberrations have a role in the difference of myopia prevalence rates in different countries.

Numerical simulation of effect of pump distribution on spherical aberration of end-pumped laser

In order to study the spherical aberration of thermal lens when the laser crystal is pumped with the pump light distributed differently and the pump light under the end-pumping condition, in this paper we establish a single-ended pump and constant temperature thermal model to analyze the working characteristics of the Nd:YVO4 crystal. The steady state heat conduction equation and Zernike polynomials are solved, and the relationship between thermal spherical aberration and distribution of pump laser is established. The model is used in simulation, and the simulation results are further analyzed theoretically, showing that under the same pump power, the spherical aberration is greatest when the pump beam is of 2-order super-Gaussian distribution. The spherical aberration decreases with the increase of pump distribution coefficient k (except the Gaussian distribution). With the increase of pump power, the influence of pump distribution coefficient k on spherical aberration is aggravated gradually, and the difference in spherical aberration caused by different values of distribution coefficient k increases gradually. The range of strongest laser power of the 2-order super-Gaussian distribution pump is analyzed and simulated. Under same pump power, the maximum range of the strongest laser power of 2-order super-Gaussian distribution pump is 0.3-0.63 times the Gauss radius. The research methods and conclusions obtained in this paper have universal applicability and can be used for quantitatively analyzing the temperature distributions, thermal deformations, optical path difference distributions, and spherical aberration distributions of other laser crystals. At the same time, this study also provides a theoretical reference for improving spherical aberration from the perspective of changing the distribution of pump light and the laser output characteristics.

Alteration in refractive index profile during accommodation based on mechanical modelling.

The lens of the eye has a gradient refractive index (GRIN). Ocular accommodation, which alters the shape of the lens in response to visual demand, causes a redistribution of the internal structure of the lens leading to a change in the GRIN profile. The nature of this redistribution and the consequence of change in the GRIN profile are not understood. A modelling approach that considers how the GRIN profile may change with accommodation needs to take into account optical and mechanical parameters and be cognisant of individual variability in the shape and size of lenses. This study models the normalised axial GRIN profile during accommodation using reduced modelling and incorporating finite element analysis to connect inhomogenous mechanical characteristics of the lens to optical performance. The results show that simulated stretching changes the length of the plateau but does not alter the cortical gradient, which supports clinical findings. There is a very small change to the accommodated and non-accommodated profiles when normalised, yet this yields measurable changes in aberrations with around 11% and almost 13% difference in spherical aberration and astigmatism respectively. The results can be used in reconstruction of the refractive index and for investigating gradual changes with age.

Comparison of Higher-Order Aberrations and Visual Quality in Eyes Wearing Aspheric and Spherical Silicone Hydrogel Contact Lenses

Purpose: To investigate ocular higher-order aberrations (HOAs) and visual quality when wearing aspheric and spherical silicone hydrogel contact lenses. Methods: Fifty eyes of 25 myopic subjects (24.32±2.87 years; 13 females, 12 males) participated in this study. Each eye was fitted with two silicone hydrogel lenses of the following brands: Biofinity (aspheric design) and Acuvue Oasys (spherical design). Best-corrected visual acuity (VA) with high and low contrast and best-corrected contrast sensitivity (CS) at 3, 6, 12 and 18 cycles per degree (cpd) were measured under photopic and mesopic conditions. A wavefront analyzer was used to measure ocular HOAs for 4-mm and 6-mm pupils in each eye without and with the contact lenses. All measurements were conducted monocularly by having each subject to wear one lens design per one day during two days. Results: No statistically significant differences in high contrast or low contrast visual acuity (HCVA or LCVA) were found between the two lens designs under photopic and mesopic conditions. There were no significant differences in CS under photopic or mesopic conditions at other spatial frequencies, although CS under the mesopic conditions at 12 cpd was statistically significant difference between the two lens designs (p=0.012). For ocular HOAs, the level of all HOAs with 4-mm and 6-mm pupils was reduced by two lens designs compared to wearing no lens. Also, there was statistically significant difference in spherical aberration (SA) between the two lens designs within the brands with both pupil sizes (p=0.002, p=0.001, respectively); however, there were no significant differences in any other ocular HOAs between the two lens types with 4-mm or 6-mm pupils. Conclusion: Aspheric silicone hydrogel contact lenses are not clinically different in visual quality compared with spherical silicone hydrogel contact lenses.

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

Changes in pupil diameter entrained by cortically initiated changes in attention

The diameter of the pupil is affected by changes in ambient illumination, color, spatial structure, movement, and mental effort. It has now been found that pupil diameter can be affected by cognitive processes. That is, it can be entrained by alternations between broadly spread and narrowly focused attention that are cued exogenously (attention is "summoned" by the cue) or endogenously (attention changes under the perceiver's intentional control). Pupil diameter also is affected by post-eye-blink constrictions that occur most often when attention is narrowed, and possibly by changes evoked by the near reflex, although changes in attention state parsimoniously account for the entirety of the results. Changes in pupil diameter produce differences in spherical aberration that alternately blur (when the pupil dilates) and sharpen the retinal image (when the pupil constricts), affecting the relative sensitivity of large receptive fields that mediate broadly spread attention compared with smaller receptive fields that mediate more narrowly focused attention. Results for endogenously cued, intentional changes in attentional spread provide definitive behavioral evidence for cortical feedback to subcortical nuclei that control pupil diameter, either directly or through pupil-constricting eye blinks. Analyses of convergent and divergent changes in eye position indicate that the near reflex was activated long after the initiation of relatively gradual attentionally cued changes in pupil diameter, and further, that when it occurs, the near reflex facilitates ongoing changes in pupil diameter.

Effect of Variation in Derived Corneal Wavefront Aberrations by Calculation Methods on Intraocular Lens Selection

To compare topographically derived corneal wavefront aberrations between the NIDEK Magellan corneal topographer with built-in software (NIDEK Co Ltd) and VOL-CT software (Sarver and Associates) and determine their effects on intraocular lens (IOL) choice based on spherical aberration profiles. Data were collected prospectively for 28 eyes without existing corneal disease prior to undergoing cataract surgery. Corneal higher order aberrations were calculated using Zernike polynomial expansions from topographic data and compared between the builtin NIDEK software and VOL-CT software. Using two-tailed paired t tests, statistically significant (P<.05) differences were found between the two calculations at 4 mm for 4th order aberrations (NIDEK: 0.2005 μm, VOL-CT: 0.1202 μm) and 6th order aberrations (NIDEK: 0.0985 μm, VOL-CT: 0.0546 μm). Statistically significant differences were noted between the two calculations at 6 mm for 5th order aberrations (NIDEK: 0.2757 μm, VOL-CT: 0.1618 μm) and 6th order aberrations (NIDEK: 0.2641 μm, VOL-CT: 0.0920 μm). No statistically significant differences existed for 3rd order, spherical aberration, and total higher order aberrations. However, using spherical aberration-based IOL selection criteria, the ultimate IOL selection would have differed in 13 eyes if calculated using the NIDEK versus VOL-CT software. Statistically significant differences were present in wavefront aberration calculations using the NIDEK versus VOL-CT software for 4- and 6-mm pupil sizes. These differences in spherical aberration could influence wavefront-optimized IOL selection for cataract surgery.

Spherical aberration and higher order aberrations with Balafilcon A (PureVision) and Comfilcon A (Biofinity)

Advances in the optical design of soft contact lenses have seen certain manufacturers incorporate aspheric optics into soft lenses in an attempt to reduce spherical aberration, to provide superior visual performance. The aim of this study is to determine the on-eye differences in spherical aberration and higher order aberrations (HOA) between the Bausch and Lomb PureVision (Balafilcon A) and the CooperVision Biofinity (Comfilcon A). Twenty subjects were recruited in a prospective, randomized, unilateral study. The right eye was dilated and HOA measured with the NIDEK OPD-Scan. Each eye was fitted randomly with a -3.00D PureVision and a -3.00D Biofinity, and HOA were measured with lenses in situ across a 6 mm pupil. Paired t-tests were performed to determine HOA differences with the lenses in situ compared to baseline. Aberrometry was successfully performed on all subjects. Statistical analysis indicated no changes in spherical aberration, but changes in other HOA. With the PureVision, there were increases in Zernike terms Z (3) (1) (from 0.01 μm to -0.11 μm), Z (4) (-2) (from 0.01 μm to 0.13 μm) and Z (5) (-1) (from -0.01 μm to 0.03 μm). With the Biofinity there was an increase in Zernike term Z (3) (3) (from 0.00 μm to 0.09 μm). No statistically significant changes occurred in spherical aberration. The PureVision caused statistically significant increases in Z (3) (1) , Z (4) (-2) and Z (5) (-1) , and the Biofinity caused an increase in Z (3) (3) . Clinically significant changes (>0.1 μm) occurred with terms Z (3) (1) and Z (4) (-2) with the PureVision only.

A Prospective, Contralateral Eye Study Comparing Thin-Flap LASIK (Sub-Bowman Keratomileusis) with Photorefractive Keratectomy

To determine the differences in the visual results, pain response, biomechanical effect, quality of vision, and higher-order aberrations, among other parameters, in eyes undergoing either photorefractive keratectomy (PRK) or thin-flap LASIK/sub-Bowman keratomileusis (SBK; intended flap thickness of +/-100 microm and 8.5-mm diameter) at 1, 3, and 6 months after surgery. A contralateral eye pilot study. Fifty patients (100 eyes) were enrolled at 2 sites. The mean preoperative spherical refraction was -3.66 diopters (D) and the mean cylinder was -0.66 D for all eyes. Eyes in the PRK group underwent 8.5-mm ethanol-assisted PRK, whereas in eyes in the SBK group, an 8.5-mm, (intended) 100-microm flap was created with a 60-kHz IntraLase femtosecond laser (Advanced Medical Optics, Santa Ana, CA). All eyes underwent a customized laser ablation using an Alcon LADARVision 4000 CustomCornea excimer laser (Alcon Laboratories, Fort Worth, TX). Preoperative and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity (UCVA), corneal topography, wavefront aberrometry, retinal image quality, and contrast sensitivity. Patients completed subjective questionnaires at each visit. One- and 3-month UCVA results showed a statistically significant difference: SBK, 88% 20/20 or better vs. 48% 20/20 or better for PRK. At 6 months, UCVA was 94% 20/20 or better for PRK and 92% for SBK. At 1 and 3 months, the SBK group had lower higher-order aberrations (coma and spherical aberration; P<or=0.05); at 1, 3, and 6 months, there was no statistically significant difference in spherical aberration and vertical and horizontal coma between the 2 groups. At the 1-month follow-up, the thin-flap/SBK group demonstrated clinically and statistically significant better visual acuity than the PRK group. By 3 months, the vision in the 2 groups had begun to equalize, although the SBK eyes continued to have better vision. At 6 months, there were no statistical differences between the 2 groups. Proprietary or commercial disclosure may be found after the references.

Spherical Aberration, Contrast Sensitivity and Depth of Focus With Three Aspherical Intraocular Lenses

Purpose: To evaluate postoperative spherical aberration, contrast sensitivity and depth of focus after implanting 3 different aspheric intraocular lenses. Methods: Fifty-six eyes (18 eyes for Akreos adapt Advanced Optics (AO), 20 eyes for AcrySof IQ SN60WF and 18 eyes for Tecnis Acrylic IOL ZA9003) of 48 patients were evaluated. Internal ocular aberration including spherical aberration and higher-order aberration and contrast sensitivity were evaluated 3 months after lens implantation. In addition, visual acuities at 33 cm and 1 m distance were measured with the far vision corrected state to calculate depth of focus. Results: The total and internal ocular spherical aberration of the AO implanted group was slightly higher than the other groups with statistical significance. However, there was no statistically significant difference of contrast sensitivity and depth of focus among the 3 groups. Conclusions: A subtle difference of spherical aberration among the 3 groups without a statistically significant difference in other factors may not induce the differences of contrast sensitivities and depths of focus in each group.

Relationship between contrast sensitivity and spherical aberration: Comparison of 7 contrast sensitivity tests with natural and artificial pupils in healthy eyes

To find a contrast sensitivity test that can be used clinically to evaluate interventions aimed at minimizing spherical aberration and determine the circumstances under which these tests should be performed. Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. Contrast sensitivity tests were performed using 2 experimental designs. Design 1 was with a natural pupil under mesopic and photopic conditions. Design 2 was with a 5.0 mm artificial pupil after cycloplegia under photopic conditions only. Two computerized tests (vertical sine-modulated gratings [VSG] and Holladay circular sine-modulated patterns [HACSS]) and 5 chart tests (Pelli-Robson, acuity-measuring letter charts at low contrast [2.5% and 10%], VectorVision, and edge contrast sensitivity) were used. Spherical aberration was assessed with a Hartmann-Shack wavefront analyzer. Forty-nine healthy subjects aged 20 to 35 years (n = 24) and 55 to 70 years (n = 25) participated. Design 2 showed a significant relationship between contrast sensitivity and spherical aberration with the HACSS at 3 cycles per degree (cpd) (P = .03) and 6 cpd (P = .01) and with the VSG at 6 cpd (P = .01). Design 1 yielded no significant relationships. Using an artificial pupil, a relationship between contrast sensitivity and spherical aberration was established with the VSG and HACSS tests but not with the chart tests. No test showed a relationship using natural pupils under either lighting condition. Chart tests are unsuitable for uncovering contrast sensitivity differences related to differences in spherical aberration, as typically found in healthy phakic eyes.

Optical performance of monofocal and multifocal intraocular lenses in the human eye

To study the optical performance of intraocular lenses (IOLs) in the human eye to ascertain how multifocality affects the optical performance of refractive and diffractive technologies and the relationship to pupil size. Vissum-Instituto de Oftalmológico de Alicante, Alicante, Spain. Ten eyes each received the monofocal AcrySof MA60 IOL (Alcon) or 1 of the following multifocal pupil-dependent IOLs: diffractive AcrySof ReSTOR (Alcon) or refractive ReZoom (Advanced Medical Optics). The intraocular optical quality in vivo with 3.0 mm and 5.0 mm pupils was characterized by comparing the means of the difference between the total and corneal optical aberrations 3 months postoperatively. The main outcomes measures were total, higher-order, spherical, and coma aberrations (root-mean-square values); modulation transfer function values; point-spread function; and the Strehl ratio. The ReZoom group had higher in vivo intraocular aberrations than the AcrySof ReSTOR and AcrySof MA60 groups (P = .022). The difference in spherical aberration between the AcrySof ReSTOR and ReZoom groups was statistically significant with 5.0 mm pupils (P = .003) and 3.0 mm pupils (P = .001). The AcrySof ReSTOR group had statistically significant lower coma aberration values with a 5.0 mm pupil (P = .012); there were no differences between IOLs with a 3.0 mm pupil (P = .185). Multifocal refractive IOLs resulted in higher intraocular aberrations. The hybrid refractive-diffractive IOL was the least affected by pupil diameter in terms of intraocular aberrations and showed significantly less increase in optical aberrations when the pupil was enlarged.

Establishing Analysis Parameters for Spherical Aberration after Wavefront LASIK

To compare preoperative and postoperative spherical aberration, coma, and other higher order aberrations from wavefront LASIK at varying pupil analysis diameters and different myopic corrections, and to determine acceptable parameters for wavefront measurements. Nonrandomized retrospective chart review. Twenty-one eyes of 12 patients who had CustomCornea LASIK with the LADARVision 4000 (Alcon, Fort Worth, TX). Wavefront analyses were performed before and 3 months after CustomCornea LASIK using a 6.5-mm central optical zone and blend zone to 9.0 mm. Wavefront measurements were made with pupil analysis diameters of 5.5, 6.0, 6.5, and 7.0 mm. Myopic corrections were divided into 3 spherical equivalent subgroups: low (<3 diopters [D]), medium (3-6 D), and high (>6 D). Main outcome measures were compared based on myopic subgroup within each analysis diameter. Results were analyzed with analysis of variance and paired t tests. Spherical aberration, coma, and other higher order aberrations. There were no significant increases in coma or other higher order aberrations postoperatively or with larger analysis diameters. There was a significant increase in postoperative differences in spherical aberration between 6.5 and 7.0 mm for the >6-D myopic correction subgroup (P = 0.03). Differences between other 0.5-mm intervals and other subgroups were not significant. The largest difference between preoperative and postoperative spherical aberration occurred at the analysis diameter 0.5 mm greater than the laser optical zone for the subgroup with high myopic correction. To detect larger degrees of induced spherical aberrations, analysis diameters 0.5 mm larger than the central laser optical zone should be considered.

Effect of radial keratotomy on the contrast sensitivity function.

A group of six patients had the radial keratotomy (RK) procedure carried out on one eye only as part of the Prospective Evaluation of Radial Keratotomy (PERK) study. Contrast sensitivity was measured in the operated and unoperated eyes of these patients under conditions of maximum correction and no over-correction. Analysis of variance indicated a significant reduction in the contrast sensitivity function (CSF) of the operated eye postsurgically when compared to the operated eye for all patients. Analysis of results for individual patients indicated that three of the six patients showed significant reductions in CSF between the two eyes. Reasons for these changes are offered in terms of the change in glare produced by the surgical procedure and the difference in spherical aberration of the eye.

Chromatic Correction of Wide-Aperture Catadioptric Systems

In the Schmidt camera system, where the spherical aberration of a mirror for a selected wave-length of light may be completely corrected by a suitably figured plate at the centre of curvature, there remains a chromatic variation of spherical aberration which sets a limit to the performance on the axis and for small angles of field, and which, for large relative apertures, becomes undesirably large. The effect is commonly reduced by introducing first-order axial chromatic aberration by using a corrector plate in the form of a figured lens of finite power instead of a figured plane parallel plate, the form in which the axial and marginal thicknesses are equal being not far removed from the optimum. Fig. 1 shows the departures (measured in d wave-lengths per 25 mm. of focal length) of the C and g emergent wave-fronts from the spherical d wave-front for a Schmidt system of relative aperture f/0·7, using for the corrector plate a borosilicate crown glass, nd = 1·516, V = 64·1, the maximum aberration for g being 1·5 wave-lengths when the marginal and intermediate zonal errors are equalized. The chromatic difference of spherical aberration is, of course, of the sign corresponding to an increase of glass-path with increasing aperture.