Higher-order Aberration Measurements Research Articles

Comparison of Corneal Higher-order Aberrations Measured by Scheimpflug Camera and Placido Disc-based Topography in Korean Patients

Purpose: We compared corneal higher-order aberration (HOA) measurements between the Pentacam<sup>®</sup> HR (PC), which uses the Scheimpflug principle, and the iTrace<sup>TM</sup> aberrometer (IT), which evaluates Placido disc topography.Methods: We retrospectively analyzed 109 eyes of 87 patients without a history of ocular surface disease during the period from January 2021 to December 2022; both devices were used on the same day. We calculated the root mean square values (μm) of corneal total HOA and of the corneal 3rd- and 4th-order HOA at a pupil diameter of 4 mm. Data were compared by Bland-Altman plots for agreement analysis and Pearson correlation coefficient for correlation analysis.Results: There was no significant difference in the total HOA (<i>p</i> = 0.145), coma (<i>p</i> = 0.309), or secondary astigmatism (<i>p</i> = 0.080) between the PC and IT measurements; all other HOAs significantly differed between devices (<i>p</i> < 0.001). In the correlation analysis, the total HOA (r = 0.605, <i>p</i> < 0.001) and coma (r = 0.634, <i>p</i> < 0.001) were moderately correlated between the two devices; the other HOAs showed low degree of correlations. In the Bland-Altman plot analysis, all HOAs showed low agreement between the two devices.Conclusions: Corneal total HOA and coma measured by the two devices were significantly correlated between the two devices, but other HOAs showed significant differences in measurement and low correlations. Therefore, corneal HOA measurements cannot be interpreted interchangeably between the two devices.

Corneal Higher-Order Aberrations Measurements: Precision of SD-OCT/Placido Topography and Comparison with a Scheimpflug/Placido Topography in Eyes After Small-Incision Lenticule Extraction.

The aim of this study was to evaluate the measurements of corneal higher-order aberrations (HOAs) obtained by a new anterior segment optical coherence tomography (OCT) technique combined with a Placido topographer (the MS-39 device) in eyes with prior small-incision lenticule extraction (SMILE) and compare them to the measurements obtained by a Scheimpflug camera combined with a Placido topographer (the Sirius device). A total of 56 eyes (56 patients) were included in this prospective study. Corneal aberrations were analyzed for the anterior, posterior, and total cornea surfaces. Within-subject standard deviation (Sw), test-retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. The differences were evaluated by paired t-test. Bland-Altman plots and 95% limits of agreement (95% LoA) were used to evaluate the agreement. High repeatability was observed for anterior and total corneal parameters, with Sw value < 0.07, TRT ≤ 0.16, and ICCs > 0.893, but not trefoil. For the posterior corneal parameters, ICCs varied from 0.088 to 0.966. Regarding interobserver reproducibility, all Sw values were ≤ 0.04 and TRT ≤ 0.11. ICCs ranged from 0.846 to 0.989, from 0.432 to 0.972, and from 0.798 to 0.985 for the anterior, total, and posterior corneal aberrations parameters, respectively. The mean difference in all aberrations was ≤ 0.05μm. All parameters showed a narrow 95% LoA. The MS-39 device achieved high precision in both anterior and total corneal measurements; the precision of posterior corneal higher-order RMS, astigmatism II, coma, and trefoil was lower. The two technologies used by the MS-39 and Sirius devices can be used interchangeably for measuring corneal HOAs after SMILE.

Scheimpflug-Derived Corneal Lower and Higher Order Aberrations Post Intrastromal Corneal Ring Segments for Keratoconus.

Intrastromal corneal ring segments (ICRS) improve corneal topographic symmetry and reduce corneal aberrations through regularization of the corneal surface, thereby functioning as a viable surgical intervention for patients with keratoconus. This study aims to evaluate changes in lower- (LOAs) and higher-order aberrations (HOAs) amongst varying pupil sizes pre- and post- ICRS implantation in keratoconus patients. We specifically investigate the impact of pupil size on total corneal HOAs up to the 6th order. Twenty-one eyes that underwent ICRS implantation were included in this prospective interventional study. LOAs and HOAs measurements at the 6 mm, 4 mm, and 2 mm pupil diameters were collected preoperatively and at 6 months postoperatively using the Zernicke analysis function on a Scheimpflug device. ICRS implantation demonstrated a statistically significant effect in vertical coma with a -0.23 reduction (p = 0.015) for a 4 mm pupil size and a -1.384 reduction (p &lt; 0.001) for 6 mm, with no significant effect at 2 mm. Horizontal coma, astigmatism 0°, astigmatism 45°, trefoil 5th order 30°, and RMS HOA demonstrated significant reductions at 4 mm or 6 mm pupil sizes but not at 2 mm. Our analysis demonstrates a favorable effect of ICRS implantation on larger pupil sizes, suggesting the importance of pupil size as it correlates with HOAs reduction.

Analysis of higher-order aberrations in relation to the clinical outcome of an enhanced monofocal IOL.

To analyse higher-order aberrations of an enhanced monofocal aspheric intraocular lens (IOL) in relation to the clinical outcome compared to a monofocal aspheric IOL. Department of Ophthalmology, Charité - Universitätsmedizin Berlin, Germany. Prospective, monocentric, controlled, non-randomized, two-armed study. After phacoemulsification, a total of 30 patients (60 eyes) were bilaterally implanted with either TECNIS Eyhance IOL model ICB00 (Johnson & Johnson Surgical Vision, Inc.) or TECNIS Monofocal 1-Piece IOL model ZCB00 (Johnson & Johnson Surgical Vision, Inc.) in 30 eyes each. Assessments were performed 1 and 3 months after surgery including refraction, uncorrected and best-corrected distance, intermediate and near visual acuity, defocus curves, contrast sensitivities under photopic, mesopic and mesopic conditions with glare, higher-order aberrations (HOAs) at pupil sizes of 5, 4, 3 and 2 mm and patient satisfaction. At 3-month follow-up, measurements of HOAs revealed significant higher negative internal and ocular primary spherical aberrations in the ICB00 group at pupil sizes of 5, 4, 3 and 2 mm. The ICB00 showed significant better results in intermediate and near visual acuity, but no difference in distance visual acuity. No significant difference was found in contrast sensitivities at any condition or spatial frequency. Spectacle independence was significant better without significant higher rates of dysphotopsia in the ICB00 group. Higher negative spherical aberrations in the ICB00 group at all measured pupil sizes appear to lead to a superior clinical outcome in intermediate and near vision compared to the ZCB00 group without compromising contrast sensitivity or distance visual acuity.

The Effect of Monochromatic Aberrations of the Cornea on Contrast Sensitivity under Photopic and Mesopic Conditions

Purpose: Vision is one of the most important senses. The first stage of vision is the creation of the observed object’s image on the retina. The quality of the retinal image is affected by several factors, such as diffraction, sampling on the retina, chromatic aberration, scattering and higher order aberrations. The measurement of the quality is achieved both with subjective (visual acuity, contrast sensitivity) and objective methods (PSF, MTF, Strehl ratio, RMS). The purpose of this project is the measurement of higher order aberrations of the anterior corneal surface (with a Placido corneal topographer) and of the contrast sensitivity (with a Pelli Robson optotype). Then, we will try to find if there is a correlation between them.&#x0D; Methods and Materials: 20 persons participated in this survey, divided in two groups of 10 persons each. The first group (group 1) included subjects up to 39 years old and the second group (group 2) from 40 years and up. The participants didn’t have any pathological problems, except lower order refractive errors. Both eyes of each individual were included in the procedure. First, the higher order aberrations of the anterior corneal surface were measured, with the implementation of a Placido corneal topographer. This was followed by a measurement of the contrast sensitivity. The whole procedure took place under two lighting conditions, both photopic and mesopic. The examination presentation of the higher order aberrations is performed with the use of Zernike polynomials.&#x0D; Results: The results of the measuring procedure showed that for the first group, under photopic conditions (luminance 32.70 cd/m2) the mean value (± standard deviation) for the higher order aberrations RMS and decimal logarithm contrast sensitivity was 0.073 ± 0.018μm and 1.54 ± 0,16 (contrast 2.88 ± 1.24%) respectively. For the second group the corresponding values were 0.080 ± 0.036μm and 1.59 ± 0.16 (contrast 2.57 ± 1.24%). Accordingly, under mesopic conditions (luminance 1.14 cd/m2) the values for the first group were 0.252 ± 0.064 μm and 1.27 ± 0.15 (contrast 5.37 ± 2.06%), while for the second were 0.253 ± 0.069μm and 1.32 ± 0.12 (contrast 4.79 ± 1.35%). Spherical aberration and coma (horizontal and vertical) were also measured for both groups under photopic and mesopic conditions. The results showed that for the first group, under photopic conditions, RMS for coma and spherical aberration is 0.033 ± 0.014 μm and 0.022 ± 0.011 μm respectively, while for the second group 0.041 ± 0.027 μm and 0.024 ± 0.008 μm. Under mesopic conditions, the relevant results are 0.139 ± 0.065 μm and 0.124 ± 0.035μm for the first group and 0.149 ± 0.066 μm and 0.107 ± 0.038 μm for the second group.&#x0D; Finally, we should mention here that the equivalent defocus error corresponding to the higher order aberration RMS was estimated. The results for all the participants (without age separation), are 0.23 ± 0.09D (photopic conditions) and 0.28 ± 0.07D (mesopic conditions).&#x0D; Conclusions: From the statistical analysis of the results we conclude that there exists a symmetry between left and right eyes regarding higher order aberrations. Furthermore, it seems that age is not a significant factor for differences on the magnitude of higher order aberrations both under photopic and mesopic conditions as well. Similar conclusions are also reached for the contrast sensitivity measurements. In addition, we have observed that a correlation exists between the higher order aberrations of the anterior corneal surface and the contrast sensitivity, for both photopic and mesopic conditions. Correlation also exists between coma and contrast only under photopic conditions. But there is no significant correlation between spherical aberration and contrast. The age difference of these two groups has not an effect on the results. Finally, the equivalent defocus is too small, both for photopic and mesopic conditions and between each other, in order to be clinically significant.

Repeatability and reproducibility of corneal higher-order aberrations measurements after small incision lenticule extraction using the Scheimpflug-Placido topographer

BackgroundTo evaluate the precision of corneal higher-order aberrations measurements after small incision lenticule extraction (SMILE) using the Sirius Scheimpflug-Placido topographer (CSO, Italy).MethodsSeventy-five eyes from 75 postoperative subjects were included in this prospective study. Three consecutive corneal aberrometric measurements were obtained with the Scheimpflug-Placido topographer by two experienced operators to assess intra- and inter-observer reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and the intraclass correlation coefficient (ICC) were calculated.ResultsFor intraobserver repeatability of anterior and total corneal aberrations, all ICCs were more than 0.922, except for trefoil (0.722 to 0.768). The ICCs of total root mean square (RMS), coma Z (3, ± 1), and spherical aberration Z (4, 0) were over 0.810 while higher-order RMS, trefoil Z (3, ± 3), and astigmatism II Z (4, ± 2) were below 0.634 for posterior corneal surface aberrations. All Sw values for all types of aberrations were equal to or below 0.07 μm. Regarding interobserver reproducibility, all TRT values were no more than 0.12 μm, 0.05 μm, and 0.11 μm for anterior, posterior, and total corneal aberrations, respectively. The ICC values ranged from 0.875 to 0.989, from 0.686 to 0.976 and over 0.834 for anterior, posterior, and total corneal aberrations, respectively.ConclusionsThe repeatability of measurements of anterior and total corneal aberrations with the Sirius system in corneas after SMILE surgery was high, except for trefoil. There was some variability in posterior corneal aberrometric measurements. High reproducibility of corneal aberrometric measurements was observed between measurements of both examiners, except for trefoil, with poor to moderate reproducibility.

Visual outcome and optical quality of a wavefront-engineered extended depth-of-focus intraocular lens.

To evaluate visual performance and optical quality of an extended depth-of-focus intraocular lens (EDoF IOL) compared with a monofocal aspheric IOL. Department of Ophthalmology, Charité-Medical University Berlin, Germany. Prospective case series. After phacoemulsification, a total of 28 patients (56 eyes) underwent bilateral implantation of either the Mini Well (EDoF IOL) or the Mini 4 (monofocal IOL). Assessments including refraction, distance, intermediate and near visual acuity, defocus curves, contrast sensitivity, glare disability, higher-order aberrations (HOAs), and patient satisfaction were performed at 1 month and 3 months postoperatively. Both study groups comprised 14 patients (28 eyes) each. At 3-month follow-up, the EDoF IOL showed better results in monocular uncorrected intermediate visual acuity (-0.04 vs 0.10 logMAR, P = .000) and in uncorrected near visual acuity (0.13 vs 0.36 logMAR, P = .000), whereas no statistically significant difference was found between groups in monocular uncorrected distance visual acuity (0.04 vs 0.00 logMAR, P = .110). The monocular depth of focus was 0.8 D greater in the Mini Well IOL group. Measurements of internal HOAs revealed a greater negative primary spherical aberration in the EDoF group at pupil sizes of 2.0 to 5.0 mm. At 5.0 mm, total internal HOAs did not differ statistically significantly (0.376 vs 0.340 μm root mean square, P = .068). The Mini Well IOL provided greater depth of focus with superior outcomes at intermediate and near distances and comparable outcomes at far distance. Although inducing higher amounts of spherical aberration, it showed good results under low lighting conditions with little subjective dysphotopsia.

Wavefront excimer laser refractive surgery for adults with refractive errors.

Wavefront excimer laser refractive surgery for adults with refractive errors.

One-Year Results of Arcuate Keratotomy in Patients With Low to Moderate Corneal Astigmatism Using a Low-Pulse-Energy Femtosecond Laser

To investigate corneal astigmatism (CA) reduction and corneal optical quality after surface-penetrating femtosecond laser arcuate keratotomies (Femto AK) considering anterior (CAant) and posterior corneal curvature (CApost), total corneal refractive power astigmatism (CAtot), and corneal higher-order aberrations (HOAs) through 1 year. Prospective interventional case series. Setting: Department of Ophthalmology, Medical University of Vienna. PatientPopulation: Forty-three eyes of 43 patients with age-related cataract and CAtot between 1 and 3 diopters (D). Paired keratotomies were created with a low-energy femtosecond laser (LDV Z8; Ziemer Ophthalmic Systems, Port, Switzerland) and combined with an astigmatic neutral manual posterior-limbal cataract incision. CA and HOAs measurements were obtained preoperatively and after 1month, 3months, and 1 year. MainOutcomeMeasure: Change of CA and HOAs after low-energy Femto AK through 1 year. Mean preoperative CAant and CAtot (1.62 ± 0.49 D and 1.58 ± 0.44 D) were significantly reduced, to 0.66 ± 0.38 and 0.50 ± 0.30 D (P < .001) 1 year after surgery, respectively. CApost showed no significant change, from 0.31 ± 0.19 D preoperatively to 0.31 ± 0.13 D (P= .732) at the 1-year follow-up period. Astigmatism as calculated by vector astigmatism analysis stayed stable at 1month, 3months, and 1 year. Corneal wavefront HOAs significantly improved at 1month, 3months, and 1 year. Paired surface-penetrating keratotomies created by a low-energy femtosecond laser showed efficient and stable CA reduction within 1 year after surgery. The optical quality of the cornea was preserved with lower HOAs than preoperatively.

Supracor LASIK treatment of hyperopic and myopic presbyopes: a comparative study

Background Supracor is a relatively new technique that has been approved for hyperopic presbyopia correction; however, till now, no published studies have evaluated the performance of supracor in myopic patients with presbyopia. Objective The aim of this study was to compare the results of supracor treatment of presbyopia between hyperopic and myopic patients. Patients and methods The study included two groups: hyperopic group and myopic group. Complete preoperative examination consisted of cycloplegic and manifest refraction, spherical equivalent (SE), binocular uncorrected and corrected distant visual acuity (UCDVA and CDVA), binocular uncorrected and corrected near visual acuity (UCNVA and CNVA), measurement of higher order aberrations, and the determination of the dominant eye using hole-in-the card test. Patients were examined at the first day, third day, 1 month, 3 months, and 6 months postoperatively. UCDVA, CDVA, UCNVA, CNVA, higher order aberrations, and SE were measured, and all complications were recorded. Furthermore, patient’s satisfaction was documented by a detailed questionnaire. All data were collected, analyzed, and compared between the two groups. Results The study included 20 hyperopic and 19 myopic patients. There were no statistically significant differences (P>0.05) between the two groups regarding postoperative UCDVA, CDVA, UCNVA, CNVA, SE, spherical aberrations, and complications. However, there was a statistically significant difference (P<0.05) between the studied groups regarding patient satisfaction at 1 month, 3 months, and 6 months postoperatively (which was higher in patients with hyperopia), with a significant increase in patient satisfaction in those with hyperopia over time. Conclusion Supracor was found to be effective, predictable, and stable technique in the management of presbyopia in both patients with myopia and those with hyperopia, with similar results in the two groups except for patient satisfaction, which was higher in those with hyperopia.

Objective Evaluation Of On-Eye Optical Quality Of Daily Disposable Silicone Hydrogel Contact Lens With Internal Wetting Agents.

PurposeTo investigate the on-eye optical quality of a daily disposable silicone hydrogel contact lens with internal wetting agent.Patients and methodsStudy subjects were daily disposable soft contact lens wearers (N=20) who were instructed to wear daily disposable hydrogel etafilcon A lens (without added wetting agent) or daily disposable silicone hydrogel senofilcon A lens (with an internal wetting agent), for a week. Subjects wore their respective lenses bilaterally and disposed of the pair of lenses daily. At the end of the 1-week test-wear period, the on-eye visual performances of the lens and the ocular surfaces were evaluated. A wavefront sensor measured sequential ocular higher-order aberrations (HOAs) for 10 s after the blink. The aberration data were analyzed in the central 4-mm diameter up to the sixth-order Zernike polynomials. Total HOAs, fluctuation index (FI), and stability index (SI) of the total HOAs over time were compared between the two lenses. Ocular surface evaluation with fluorescein was performed following the wavefront measurement.ResultsThe senofilcon A lens had significantly lower average total HOAs, FI, and SI (p<0.001, p=0.001, p=0.007, respectively) than the etafilcon A lens. After 1-week wear of each lens, corneal staining was observed in eight subjects (40%) with the etafilcon A lens and in two subjects (10%) with the senofilcon A lens. The senofilcon A lens had significantly lower incidence of corneal staining than the etafilcon A lens (p=0.041).ConclusionQuantitative sequential measurement of HOAs objectively showed the possibility of better and more stable optical quality with silicone hydrogel daily disposable contact lens with the internal wetting agent than with hydrogel lens without the added wetting agent.

Noninvasive imaging of the tree shrew eye: Wavefront analysis and retinal imaging with correlative histology

Tree shrews are small mammals with excellent vision and are closely related to primates. They have been used extensively as a model for studying refractive development, myopia, and central visual processing and are becoming an important model for vision research. Their cone dominant retina (∼95% cones) provides a potential avenue to create new damage/disease models of human macular pathology and to monitor progression or treatment response. To continue the development of the tree shrew as an animal model, we provide here the first measurements of higher order aberrations along with adaptive optics scanning light ophthalmoscopy (AOSLO) images of the photoreceptor mosaic in the tree shrew retina. To compare intra-animal in vivo and ex vivo cone density measurements, the AOSLO images were matched to whole-mount immunofluorescence microscopy. Analysis of the tree shrew wavefront indicated that the optics are well-matched to the sampling of the cone mosaic and is consistent with the suggestion that juvenile tree shrews are nearly emmetropic (slightly hyperopic). Compared with in vivo measurements, consistently higher cone density was measured ex vivo, likely due to tissue shrinkage during histological processing. Tree shrews also possess massive mitochondria (“megamitochondria”) in their cone inner segments, providing a natural model to assess how mitochondrial size affects in vivo retinal imagery. Intra-animal in vivo and ex vivo axial distance measurements were made in the outer retina with optical coherence tomography (OCT) and transmission electron microscopy (TEM), respectively, to determine the origin of sub-cellular cone reflectivity seen on OCT. These results demonstrate that these megamitochondria create an additional hyper-reflective outer retinal reflective band in OCT images. The ability to use noninvasive retinal imaging in tree shrews supports development of this species as a model of cone disorders.

Corneal higher-order aberrations measurements: Comparison between Scheimpflug and dual Scheimpflug–Placido technology in keratoconic eyes

To compare the difference and agreement of corneal higher-order aberrations (HOAs) in keratoconic eyes using Scheimpflug and dual Scheimpflug-Placido imaging systems. Emory University, Atlanta, Georgia, and the University of Southern California, Los Angeles, California, USA. Retrospective between-devices reliability and agreement study. Patients diagnosed with keratoconus were evaluated sequentially by Scheimpflug and dual Scheimpflug-Placido devices. Differences, correlations, and agreement between values for total root mean square (RMS), trefoil, coma, and spherical aberration were analyzed, and Bland-Altman plots were generated. Fifty eyes from 50 patients (31 men, 19 women) were evaluated. Trefoil at 30 degrees, spherical aberration, and total RMS were significantly different between groups (P<.05), whereas trefoil at 0 degrees and total coma values were not statistically different. There was a weak positive correlation between devices for trefoil at 0 degrees (r=0.228), and a moderate positive correlation for trefoil at 30 degrees (r=0.473), horizontal coma (r=0.430), and for total corneal RMS (r=0.637). Vertical coma (r=0.816) and spherical aberration (r=0.874) showed a strong positive correlation. The 95% limits of agreement (LoA) for absolute values were 1.963μm for trefoil at 30 degrees, 2.449μm for trefoil at 0 degrees, 3.530μm for horizontal coma, 2.145μm for vertical coma, 1.242μm for spherical aberration, and 10.527μm for RMS. Significant differences were found between measurements of corneal HOAs generated by Scheimpflug and dual Scheimpflug-Placido devices in patients with keratoconus, with generally limited correlations and wide LoA. HOAs measurements from these devices should not be considered equivalent.

Higher-order aberration measurements: Comparison between Scheimpflug and dual Scheimpflug–Placido technology in normal eyes

To compare higher order aberrations (HOAs) in normal eyes between a Scheimpflug imaging system (Pentacam HR) and dual Scheimpflug-Placido imaging system (Galilei G4). Emory University, Atlanta, Georgia, and the University of Southern California, Los Angeles, USA. Retrospective case series. Eyes screened for refractive surgery were evaluated sequentially using a Scheimpflug device and a dual Scheimpflug-Placido device. Differences, correlations, and agreement between values for total root mean square (RMS), trefoil, coma, and spherical aberration were analyzed, and Bland-Altman plots were generated. One hundred five eyes of 105 patients (44 men, 61 women) were evaluated. Total RMS, coma, and trefoil were significantly different between groups (all P<.001), while spherical aberration values were not. There was moderate correlation between devices for trefoil (r=0.475 to 0.652), coma (r=0.574 to 0.651), and spherical aberration (r=0.483) and a strong correlation for total cornea RMS (r=0.817). There was no directional bias between groups. The 95% limits of agreement for absolute values was 0.039μm for trefoil at 30 degrees, 0.405μm for trefoil at 0 degree, 0.553μm for horizontal coma, 0.545μm for vertical coma, 0.318μm for spherical aberration, and 0.617μm for RMS. A Scheimpflug imaging device and dual Scheimpflug-Placido imaging device generated statistically different values for total cornea HOAs; however, the correlation between devices was moderate to strong and there was reasonable agreement in all measures for normal eyes. Based on these findings, the devices appear functionally equivalent for clinical use, although caution is warranted for outcomes-based research protocols that report HOAs.

Precision and agreement of higher order aberrations measured with ray tracing and Hartmann-Shack aberrometers

BackgroundTo assess the precision and agreement of measurements of higher order aberrations (HOAs) obtained with a ray tracing aberrometer (iTrace) and a Hartmann-Shack aberrometer (Topcon KR-1 W).MethodsProspective evaluation of the diagnostic test. Data from the right eyes of 92 normal subjects obtained using the two devices were included in this study. Two observers performed 3 consecutive scans to determine the intraobserver repeatability and interobserver reproducibility. About one week later, one observer performed an additional 3 consecutive scans to obtain the intersession reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and intraclass correlation coefficient (ICC) were used to assess the precision, while Bland-Altman plots were performed to assess the agreement.ResultsFor intraobserver repeatability of the ocular, corneal and internal HOAs, Topcon KR-1 W showed a 2.77Sw of 0.079 μm or less and ICCs of 0.761 or more; and iTrace showed a 2.77Sw of 0.105 μm or less and ICCs of 0.805 or more. The ICCs of the internal HOAs of interobserver reproducibility were less than 0.75 except for spherical aberration (SA) (0.862), and interobserver reproducibility of the counterpart showed similar but lower results. For the ocular, corneal and internal HOA measurements, statistically significant differences existed between the Topcon KR-1 W and iTrace (all P < 0.05). No significant differences were observed in the ocular SA and internal coma.ConclusionsThe ray tracing and Hartmann-Shack method aberrometers provided excellent repeatability but less reliable reproducibility in the measurement of HOAs (except for SA). The two aberrometers should not be interchangeable in clinical application because of the significant differences in HOA measurements between them.

Comparison of Higher-Order Aberration Values between Different Aberrometry Technologies in Preoperative Laser Refractive Surgery Patients

Introduction: Purpose of this study was to evaluate the inter-device agreement of ocular and corneal higher-order aberration measurements using various aberrometers. Materials and method: Ocular and corneal higher-order aberrations were measured from 57 eyes. For ocular aberration, the measurements were obtained from WASCA Analyzer (Carl Zeiss Meditec, Jena, Germany), i-Profiler Plus (Carl Zeiss Meditec, Jena, Germany) and OPD-Scan III (NIDEK Co. Ltd., Tokyo, Japan). Whereas for corneal aberration, an additional measurement was obtained from Atlas Corneal Topographer 9000 (Carl Zeiss Meditec, Jena, Germany). All the measurements were displayed by the Zernike algorithm. Root mean squares of total, 3rd and 4th order of higher-order aberrations were compared between any three devices using repeated measured analysis of variance. The Bland-Altman analysis and Pearson's correlation were employed to assess agreement and strength of relationship between measurements. Results: For ocular aberrations, there were no significant difference (P &gt; 0.05) in all comparisons except for total higher-order aberration, oblique and horizontal trefoil. Whereas for corneal aberrations, vertical coma, spherical aberration and with-therule/against-the-rule secondary astigmatism between devices were found to be significantly different (P &lt; 0.05). The most agreeable device pairs for ocular and corneal aberrations were demonstrated by i-Profiler Plus - OPD Scan III (95% limit of agreement: -0.340 to 0.730) and Atlas Corneal Topographer 9000 - i-Profiler Plus (limit of agreement: 0.196 to 0.520) respectively. The r-values are stronger than 0.70. Conclusion: There were differences in the value of higher-order aberrations between different aberrometry technologies. Clinical impact due to the differences in wavefront measurement between skiascopy, Placido-based and laser technologies need to be investigated further.

Aberrometry Repeatability and Agreement with Autorefraction.

Commercially available aberrometers are essential to clinical studies evaluating refractive error and image quality. The Discovery System (Innovative Visual Systems, Elmhurst, IL) is a promising clinical instrument that allows investigators to export aberration data for research and analysis purposes. An assessment of the Discovery System's performance is essential to the interpretation of the data obtained. The aims of this study were to determine the between-visit repeatability of refractive error and higher-order aberration measurements with the Discovery System and to examine between-instrument agreement of refractive error measurements with the Discovery System and Grand Seiko WAM-5500 open-field autorefractor (Grand Seiko Co., Hiroshima, Japan). Cycloplegic refractive error values from the Discovery System (over a 3-mm pupil) and the Grand Seiko autorefractor were converted to power vectors (M, J0, and J45), and averaged. Zernike coefficients were also calculated by the Discovery System over a 6-mm pupil through the sixth radial order. Between-visit repeatability and agreement were evaluated using Bland-Altman difference-versus-mean plots. A t-test compared each mean difference (bias) to zero, and the 95% limits of agreement were calculated. Twenty-five young adults with a mean (±SD) cycloplegic spherical-equivalent refractive error of -2.91 ± 1.85 diopters (D) (range, -6.96 to +0.74 D) were enrolled. There were no significant between-visit differences with the Discovery System for M, J0, J45, third- through sixth-order root mean square (RMS), higher-order RMS, or spherical aberration (all P > .30), and the repeatability for defocus and higher-order RMS were ±0.31 D and ±0.095 μm, respectively, for a 6-mm pupil. At a 3-mm pupil, the Discovery System, on average, measured slightly more positive values than the Grand Seiko for M (0.28 D), J0 (0.11 D), and J45 (0.12 D; all P < .005). The Discovery System was very repeatable and would be an appropriate instrument to measure cycloplegic refractive error and higher-order aberration changes in adults. Small differences in refractive error were found between the Discovery System and Grand Seiko.

Wavefront excimer laser refractive surgery for adults with refractive errors

Wavefront excimer laser refractive surgery for adults with refractive errors

Higher-order aberration 4 years after corneal collagen cross-linking.

Purpose:Corneal collagen cross-linking (CXL) is a treatment strategy used in keratoconic eyes. Evaluation of long-term changes of higher-order aberrations (HOAs) after CXL is useful in understanding the efficacy of this procedure in improving optical, refractive, and visual acuity. This study aims to investigate the long-term effect of CXL on ocular HOA in patients with progressive keratoconus (KC).Methods:Using an OPD-Scan II aberrometer, ocular HOAs measurements of 56 eyes of 56 patients that underwent CXL was evaluated at the baseline, 1, 2, and 4 years after the procedure. All OPD-Scan measurements were decomposed into Zernike coefficients from 3rd to 6th order.Results:The results revealed that except for a few parameters, most of the aberration parameters continuously decreased during the study. In the 4-year postoperative period, a statistically significant improvement in all HOA parameters except 5th order Zernike polynomials (Z51, Z5−1, Z53, Z5−3, Z55, and Z5−5) was observed. All the values significantly decreased compared to the preoperative measurements (P < 0.05). The mean ± standard deviation (SD) root mean square of the 3rd, 4th, and the 5th order as well as coma, coma like, and total HOA parameters were significantly decreased compared to both preoperative and previous visits (P < 0.001). There were significant correlations between preoperative measurements of HOAs parameters with best-corrected visual acuity (BCVA) including Z31, Z3−1, Z40, Z51, and Z42. Moreover, all the HOAs parameters in 4 years after the CXL were significantly correlated with BCVA (P < 0.05).Conclusion:CXL is effective in improving HOA parameters in eyes with progressive KC during a long-term follow-up.

Correlations between Corneal and Internal Wavefront Aberrations through Zernike Coefficients Analysis

Objectives: To examine corneal aberrations are offset by internal aberrations more closely, the Zernike coefficients of corneal aberrations and internal aberrations were compared and analyzed. Methods/Statistical Analysis: Measurements of higher-order aberrations were performed with KR-9000 PW (Topcon Corp., Japan), a Hartmann-Shack Wavefront aberrometer. The coefficients from the 2nd to 4th expressions on Zernike Polynomials were analyzed for cornea and internal optics within 6mm measurement zone. 342 healthy eyes of 171 young adults who have never received eye surgery and do not wear contact lenses were selected as subjects of this study. Findings: There were significant negative correlations among all Zernike coefficients of corneal and internal aberrations. In Z31(r=-0.887, p=0.00), Z4-4(r=-0.698, p=0.00), and Z44(r=-0.688, p=0.00), there were high correlations between corneal and internal aberrations. On the other hand, the correlation coefficients of Z20 and Z22 that belonged to lower-order aberration were very weak at -0.129 and -0.136 respectively, having almost no correlation. Improvements/Applications: Since some signs of their Zernike coefficients are different, it is considered necessary to analyze not the both eyes but a single eye to identify the accurate RMS values of each Zernike coefficients and not only the correlations.