Repeatability of wavefront measurements in pseudophakic eyes (original) (raw)
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Clinical and Experimental Optometry, 2009
Background: Clinical aberrometers are accurate, robust instruments for measuring wavefront aberrations for foveal vision but several practical concerns arise when performing aberrometry of the peripheral field. The purpose of this study was to evaluate these concerns experimentally using a physical eye model. Methods: A physical model eye was constructed to provide a stable test case that resembled a human eye. Aberrations were measured with a commercial Shack-Hartmann aberrometer along lines-of-sight ranging from zero to 45°of eccentricity. Commercial software for wavefront reconstruction and Zernike analysis was adapted for use with elliptical entrance pupils encountered off-axis. Results: Pupil dimensions estimated from the array of Shack-Hartmann spots captured by the wavefront sensor followed geometrical optics predictions up to 30°eccentricity. With careful attention to detail, aberration analysis over an elliptical pupil was verified with alternative software. Retinal image quality declined slowly as eccentricity increased due to the eye model's spherical aberration. The total RMS computed from Zernike coefficients overestimated the total RMS computed based on the wavefront error of the elliptical pupil. Conclusion: Measurement of off-axis wavefront aberrations of a model eye over a restricted range of eccentricities is possible with the COAS clinical wavefront aberrometer and auxiliary lenses to correct astigmatism. When central image quality is good, the off-axis aberrations will have a powerful effect on peripheral image quality. When central image quality is poor, the additional effect of off-axis aberrations will be minor.
BMC ophthalmology, 2004
Recently, instruments for the measurement of wavefront aberration in the living human eye have been widely available for clinical applications. Despite the extensive background experience on wavefront sensing for research purposes, the information derived from such instrumentation in a clinical setting should not be considered a priori precise. We report on the variability of such an instrument at two different pupil sizes. A clinical aberrometer (COAS Wavefront Scienses, Ltd) based on the Shack-Hartmann principle was employed in this study. Fifty consecutive measurements were performed on each right eye of four subjects. We compared the variance of individual Zernike expansion coefficients as determined by the aberrometer with the variance of coefficients calculated using a mathematical method for scaling the expansion coefficients to reconstruct wavefront aberration for a reduced-size pupil. Wavefront aberration exhibits a marked variance of the order of 0.45 microns near the edge...
Clinical Ophthalmology, 2011
The purpose of this study was to evaluate the correlation between contrast sensitivity and calculated higher-order aberrations based on individual natural pupil diameter after cataract surgery. Methods: This prospective study included 120 eyes from 92 patients who were randomized to receive one of four lenses, including three aspheric lenses (Acrysof SN60WF, Tecnis ZA9000, and Hoya Py60AD) and one spherical lens (Acrysof SN60AT). Contrast sensitivity, higher-order aberrations of the whole eye, and pupil diameter under photopic and mesopic conditions were measured 1 month postoperatively. Higher-order aberrations were decomposed into Zernike coefficients, calculated according to individual pupil diameter. The correlation between higherorder aberrations and contrast sensitivity was evaluated. Results: There were no significant differences in contrast sensitivity function between the four types of lenses under photopic conditions. However, the contrast sensitivity function and area under log contrast sensitivity function in the aspheric lenses were significantly better than in the spherical lens under mesopic conditions. Under mesopic conditions, spherical aberration in eyes with aspheric lenses was significantly lower than in eyes with spherical lenses (P , 0.05). Under photopic conditions, coma aberration had a significant negative correlation with contrast sensitivity at 12 cycles/degree. Under mesopic conditions, spherical aberration had a significant negative correlation with contrast sensitivity at 3, 6, and 12 cycles/degree with glare, and with contrast sensitivity at 6 and 18 cycles/degree without glare. Conclusion: In terms of influence on visual function, coma aberration may be more significant under photopic conditions and spherical aberration under mesopic conditions.
Repeatability of corneal and ocular aberration measurements and changes in aberrations over one week
Clinical and Experimental Optometry, 2009
Background: Both Shack-Hartmann aberrometry (IRX3, Imagine Eyes, Orsay, France) and Scheimpflug photography (Oculus Pentacam, Oculus Inc Wetzlar, Germany) are known to provide repeatable measurements. The variability in measurements of corneal and ocular aberrations obtained with these instruments over one week had not been assessed. The aim was to study the variability in corneal and ocular aberrations in the human eye over one week and to determine the impact of age on corneal and crystalline lens aberrations and on the variability of these measurements. Methods: Monochromatic ocular aberrations were measured with the IRX3 and monochromatic corneal aberrations were measured using Scheimpflug photography on one eye of 23 normal subjects at periods of a few seconds, one hour and one week after the initial measurement. Results: No significant differences were found between the initial aberrations and aberrations measured at 59 Ϯ 24 seconds, 1.10 Ϯ 0.24 hours and 7.11Ϯ 0.31 days later. Analysis with Bland and Altman plots showed that measurements with both instruments were highly repeatable over the times studied. There was no relationship between age and the variance of corneal and ocular aberrations (higher order, spherical and coma aberrations). Corneal spherical aberration did not show a significant correlation with age, whereas the lens aberrations changed from being negative in the younger age groups to positive in the older age group, however, these differences failed to reach statistical significance (p > 0.05). Conclusion: The variability found in all the measurements was small and not clinically significant and could be attributable to instrument noise, changes in the tear film and to small fixational eye movements.
PLOS ONE, 2015
To explore the relationship between ablation parameters of myopic laser surgery and measurement area of wavefront aberration (WA) with Hartmann-Shack wavefront sensor. Methods 58 subjects undergone myopic laser surgeries and 74 uncorrected myopic subjects were enrolled in this experiment. The laser ablation parameters were obtained from surgical records, which included spherical error (Rx), depth, and optical zone (OZ) of ablation. The measured area of WA was tested by the WASCA, and the real pupil size was tested by Pentacam. The corneal eccentricity (E value) and curvature was also measured with the Pentacam. All the measurements were performed under mydriatic condition.
International journal of ophthalmology, 2012
To study the distribution of ocular higher-order aberrations(HOAs) and mesopic pupil size in individuals screened for refractive surgery. Ocular HOAs and mesopic pupil size were studied in 2 458 eyes of 1 240 patients with myopia, myopic astigmatism and compound myopic astigmatism and 215 eyes of 110 patients with hyperopia, hyperopic astigmatism and compound hyperopic astigmatism using the Zywave aberrometer (Busch& Lomb). All patients had correctable refractive errors without a history of refractive surgery or underlying diseases. Root-mean-square values of HOAs, total spherical aberration, total coma and mesopic pupil size were analyzed. Ocular HOAs were measured across a ≥ 6.0 mm pupil, and pupil size measurements were performed under the mesopic condition. The mean values of HOAs, total spherical aberration and total coma in the myopic group were 0.369µm, ±0.233, 0.133± 0.112µm and 0.330±0.188µm, respectively. In the hyperopic group the mean values of HOAs, total spherical aber...
Optometry and Vision Science, 2003
Repeated measures of wavefront aberrations were taken along the line-of-sight of seven eyes using two instruments: an objective, cross-cylinder aberroscope (OA) and a Shack-Hartmann (SH) aberrometer. Both instruments were implemented on the same optical table to facilitate interleaved measurements on the same eyes under similar experimental conditions. Variability of repeated measures of individual coefficients tended to be much greater for OA data than for SH data. Although Zernike coefficients obtained from a single measurement were generally larger when measured with the OA than with the SH, the averages across five trials were often smaller for the OA. The Zernike coefficients obtained from the two instruments were not significantly correlated. Radial modulation-transfer functions and point-spread functions derived from the two sets of measurements were similar for some subjects, but not all. When average Zernike coefficients were used to determine optical quality, the OA indicated superior optics in some eyes, but the reverse trend was true if Zernike coefficients from individual trials were used. Possible reasons for discrepancies between the OA and SH measurements include difference in sampling density, quality of data images, alignment errors, and temporal fluctuations. Multivariate statistical analysis indicated that the SH aberrometer discriminated between subjects much better than did the objective aberroscope. (Optom Vis Sci 2003;80:15-25)
Refractive surgery corrects lower-order refractive aberrations (sphere and astigmatism), but in many cases it inadvertently creates large higher-order aberrations that can degrade vision. This has prompted the development of new instruments, aberrometers, which measure higher-order aberrations. We evaluated a new clinical aberrometer, the Complete Ophthalmic Analysis System (COAS) for accuracy, repeatability and instrument myopia. We measured 56 normal eyes (28 subjects) using the COAS, with and without cycloplegia and evaluated its lower-order accuracy in comparison to clinical subjective refraction. We also evaluated lower- and higher-order repeatability and instrument myopia. Data were analyzed for a 5.O-mm diameter pupil. For comparison, some of these analyses were also performed on a conventional auto refractor. Mean COAS accuracy for lower-order aberrations (sphere and astigmatism) was at least as good as clinical subjective refraction. Lower-order repeatability was similar to...
Journal of Current Ophthalmology, 2016
Purpose: To evaluate the correlation between refractive, corneal, and residual astigmatism and higher order aberrations (HOA) in refractive surgery candidates. Methods: Three hundred and seventy-five eyes of 188 patients aged 28.2 ± 6.24 years with a predominance of females (62.7%) were enrolled in this study. Refraction, topography (Orbscan IIz, Bausch & Lomb, Rochester, NY, USA), and aberrometry (Zywave, Bausch & Lomb, Rochester, NY, USA) were performed to determine refractive and corneal astigmatism and HOA for all participants. Ocular residual astigmatism was calculated using vector analysis. Results: The mean spherical equivalent was À3.59 ± 1.95 D and the mean refractive astigmatism was À1.97 ± 1.3 D. The mean HOA was 0.38 ± 0.15 mm in all cases, which increased with spherical equivalent (p < 0.05). There was a positive significant correlation between both corneal and refractive astigmatism and HOA (p < 0.05), but there was no significant correlation between residual astigmatism and HOA (p ¼ 0.122). Conclusion: The results of the study showed significant correlations between corneal and refractive astigmatisms and HOA.
Measurement repeatability of corneal aberrations
Journal of refractive surgery (Thorofare, N.J. : 1995)
Customized procedures that aim to improve visual performance beyond traditional sole correction of sphere and cylinder require the reliable determination of higher order corneal and ocular aberrations for individual eyes. The aim of the current investigation was to determine the repeatability of corneal aberration measurement. Ten subjects were measured on 10 different days using a videokeratoscope. The Zernike coefficients and the wavefront error were calculated from the height data files using CTView. Repeatability was calculated for apertures of 3, 4.5, and 6 mm at the 95% confidence level. The wavefront error absolute repeatability was similar for the 4th and 10th order analysis. The absolute repeatability for individual Zernike coefficients was coefficient dependent; the poorest repeatability was recorded for coma-like aberrations (uncertainty 3 mm = 0.060 microm; 4.5 mm = 0.083 microm; 6 mm = 0.109 microm). The relative repeatability compared to the population means was good f...