Validation of an Off-Eye Contact Lens Shack-Hartmann Wavefront Aberrometer (original) (raw)
Related papers
Optical Review, 2006
To assess optical characteristics of bifocal soft contact lenses (BCLs) in use, we measured wavefront aberrations of human eyes, of eyes with a monofocal soft contact lens (MCL), and of eyes with a BCL. Modulation transfer functions (MTFs), Strehl ratios, and simulated images for far and near vision were produced with the measured aberrations. High order aberrations of subject 1 were significantly smaller than those of subject 2 (t-test, P ¼ 0:001). We found that wearing the BCL improved the optical quality of an eye in subject 1, expressed as the horizontal MTF from 2 to 48 cycles per degree (cpd) for near vision and the Strehl ratio (t-test, P ¼ 0:009 for Strehl ratio). But we did not find the same effect in subject 2. This difference may be due to the difference in the aberrations of the eyes of the two subjects.
Clinical and Experimental Optometry, 2009
Introduction: Advances in contact lens design technology allow incorporation of correction of higher-order aberrations to improve or manipulate the eye's optical quality. Repeatability of aberration measurements in vivo with contact lens wear has not been established. Method: Higher-order aberrations were measured using the COAS aberrometer (Wavefront Sciences, USA) in 23 participants who were free from external eye pathology. Cycloplegia with 1% Cyclopentolate HCl ensured control of accommodation and that pupil diameters exceeded analysis diameter. Tear film characteristics were assessed with the phenol red thread test and Keeler Tearscope. Variability in wavefront aberrations was assessed with and without a low powered soft contact lens. The effect of time after the blink and tear film characteristics were also investigated. Results: Standard deviations differed significantly for some fifth-order terms (p Յ 0.003) with contact lens wear. Coefficient of variation did not increase significantly with contact lens wear. Time from blink increased standard deviations in the third-order (p Յ 0.003). The effect of contact lens wear and time from blink differed between groups with different tear film characteristics. Conclusions: Variability in measurements of aberrations increased significantly for oddorder aberrations when a contact lens was worn or between blinks. Fourth-order aberrations showed less effect of contact lens wear. Therefore, verification of the performance of lenses with aspheric optics on eye is feasible. Accurate assessment of higher-order aberrations is more difficult when a contact lens is worn. Both contact lens wear and time from blink increase variability in aberrations, which suggests a role for the tear film in increased aberrations with soft contact lens wear.
Wavefront aberration function from hard contact lenses obtained with two different techniques
2011
The analysis and measurement of the wavefront aberration function are very important tools in the field of visual optics; they are used to understand the performance of the human eye in terms of its optical aberrations. In recent years, we have compared, through two different methods, the wavefront aberration function of a reference refractive surface of 5 mm in diameter and we have demonstrated its equivalence1. Now, we want to extend these results to a set of hard contact lenses. These hard contact lenses have been subjected to different laser ablation techniques which are typically used in refractive surgery. Our goal is to characterize the resultant ablation profile. We show our results obtained for both, a nonablated hard contact lens and the corresponding ablated samples.
Eye & Contact Lens: Science & Clinical Practice, 2008
Purpose. To evaluate the effect of negatively powered soft contact lenses on ocular higher-order aberrations (HOAs). Methods. HOA measurements were performed with fixed optical zones of 4.0 and 6.0 mm on 20 eyes of 10 participants before and minutes after wearing extended-wear Focus NIGHT & DAY contact lenses. For each eye, three contact lens powers were used: Ϫ2.00 diopters (D),-4.00 D, and a power equal to the spherical equivalent of each eye. Results. The change in spherical aberration was highly correlated with the change in negative power of the contact lens at an optical zone of 4 and 6 mm (Pearson correlation coefficient ϭ 0.914 and 0.743, respectively, PϽ0.0001). Total HOAs had a weaker but important correlation at an optical zone of 6 mm (Pearson correlation coefficient ϭ 0.470, Pϭ0.037) and insignificant correlation at an optical zone of 4 mm. Coma and trefoil were poorly correlated with contact lens power in either optical zone. Compared to the control using both optical zones, the-2.00 D contact lens resulted in a significant increase in total HOAs and spherical aberration, whereas the-6.00 D lens yielded a marked decrease in spherical aberration and a mild, statistically insignificant increase in total HOAs. Both contact lens powers yielded larger ocular coma and unchanged trefoil levels. The change from induction to reduction of spherical aberration occurred at-4.00 D. Conclusions. The Focus NIGHT & DAY lens vehicle harbors positive spherical aberration and coma, independently of the lens power. The negative power of contact lenses induces negative spherical aberration, which, at large values, compensates for the lens vehicle positive spherical aberration to produce a net negative spherical aberration.
Multimodal characterization of contact lenses
Optifab 2015, 2015
A table top instrument has been designed, constructed and tested to characterize all of the primary optical and physical properties of contact lenses. Measured optical properties include base power, cylinder power, cylindrical axis, prism, refractive index and wavefront aberrations. Measured physical properties include center thickness, lens diameter and lens sagittal depth. The instrument combines a Shack-Hartmann wavefront sensor (SHWS), a machine vision sensor, and a low coherence light interferometer (LCI) all coaxially aligned into a single tabletop unit. The unit includes a cuvette, mounted in a translatable sample chamber for holding the contact lens under test, and it can be configured to measure wet or dry contact lenses. During operation, the vision sensor measures the diameter of the lens, and locates the center of the lens. The lens is then aligned for other measurements. The vision sensor can also measure various alignment marks on the lens, as well as identify any alpha numerical features, which can be used to associate the lens orientation with the measured aberrations. The LCI measures the center thickness, sagittal depth and index of refraction of the contact lens. The base radius of curvature is then calculated using these measured parameters. The SHWS measures the lenses prescription power, including spherical, cylinder, prism, and higher order wavefront aberrations. NIST traceable calibration artifacts are used to calibrate the SHWS, machine vision and LCI modalities. Repeatability measurements on a contact lens in a saline solution are presented.
Evaluating the Wavefront Aberration Properties of Senofilcon A Photochromic Contact Lenses
2021
Purpose To assess the wavefront aberrations of photochromic senofilcon A contact lenses in both activated and inactivated states.Methods In this cross-sectional study, 20 subjects who had previously used soft contact lenses were enrolled. Corneal topography and aberrometry measurements were performed on each subject during one session with Sirius Scheimpflug-Placido topography (Sirius, Costruzione Strumenti Oftalmici, Italy). Following the first measurement of an eye without a contact lens, the measurements were performed with the photochromic contact lens in the inactivated and activated states, respectively. The corneal topographic [flattest keratometry (K1), steepest keratometry (K2), the axis of the steep meridian (Axis)] and aberrometric [root-mean-square (RMS) of aberrations; optical path difference (OPD), higher-order (HOA), astigmatism, coma, spherical aberration, and residual aberration] measurements were evaluated.Results The average contact lens sphere power was -2.33 ± 1...
Peripheral Aberrations and Image Quality for Contact Lens Correction
Optometry and Vision Science, 2011
Purpose-Contact lenses reduced the degree of hyperopic field curvature present in myopic eyes and rigid contact lenses reduced sphero-cylindrical image blur on the peripheral retina, but their effect on higher order aberrations and overall optical quality of the eye in the peripheral visual field is still unknown. The purpose of our study was to evaluate peripheral wavefront aberrations and image quality across the visual field before and after contact lens correction. Methods-A commercial Hartmann-Shack aberrometer was used to measure ocular wavefront errors in 5° steps out to 30° of eccentricity along the horizontal meridian in uncorrected eyes and when the same eyes are corrected with soft or rigid contact lenses. Wavefront aberrations and image quality were determined for the full elliptical pupil encountered in off-axis measurements. Results-Ocular higher-order aberrations increase away from fovea in the uncorrected eye. Third-order aberrations are larger and increase faster with eccentricity compared to the other higher-order aberrations. Contact lenses increase all higher-order aberrations except 3 rd-order Zernike terms. Nevertheless, a net increase in image quality across the horizontal visual field for objects located at the foveal far point is achieved with rigid lenses, whereas soft contact lenses reduce image quality. Conclusions-Second order aberrations limit image quality more than higher-order aberrations in the periphery. Although second-order aberrations are reduced by contact lenses, the resulting gain in image quality is partially offset by increased amounts of higher-order aberrations. To fully realize the benefits of correcting higher-order aberrations in the peripheral field requires improved correction of second-order aberrations as well.
Limitations of the ocular wavefront correction with contact lenses
Vision Research, 2009
We analyze theoretically, by means of both computer simulations and laboratory experiments, the limitations of correcting aberrations with ideal customized contact lenses. Four experiments are presented: In the first one, we have analyzed the limitations of a static correction on the dynamic wavefront. In the second one, we studied the rotations of a contact lens on the eye using an optical method. The third one researched the limitations of the wavefront correction, focusing on a group of normal and highly aberrated eyes, when the correction suffers from a permanent rotation or translation. The fourth one estimates, under a simple approximation, the error made when applying on the corneal plane the correction corresponding to the wavefront measured at the entrance-pupil plane. Results show that a static correction of the wavefront leaves a residual aberration of 0.15-0.25 lm for a 5 mm pupil. Rotation of the contact lens (up to ±4°) diminishes the effectiveness of the correction. Horizontal or vertical translations of 0.5 mm could generate a high-order-aberration RMS that is higher than the remaining one after a standard low-order correction. In particular, the group of eyes having normal values of high-order aberrations are more sensitive to translations than the one having higher values. Most of the results could be applied to other methods of aberration correction, such as refractive surgery or correction by means of intraocular lenses.
Accuracy of the Hand-held Wavefront Aberrometer in Measurement of Refractive Error
Korean Journal of Ophthalmology, 2020
Uncorrected refractive errors are a major cause of amblyopia, which interrupts social functioning and academic performance in children [1]. It is estimated that over one billion people suffer from uncorrected refractive errors worldwide [2,3]. The incidence rate of amblyopia caused Purpose: To compare refractive error measured by hand-held wavefront aberrometers with postcycloplegic autorefraction (AR) and cycloplegic refraction (CR). Methods: The medical records of patients who received refractive measurements using the wavefront aberrometer, postcycloplegic AR, and CR between January 2014 and January 2016 were retrospectively analyzed. The mean differences, 95% confidence intervals, and limits of agreement (LOA) were calculated for the refractive vector components (M, J 0 , and J 45). Results: Fifty-one patients (9.0 ± 5.5 years, male 41.2%) were enrolled in this study, and only the right eye of each was included. Refractive errors ranged from-9.25 to +7.25 diopters (D) for spherical equivalent (median, 0.75 D). The M component was not significantly different among the three methods (p = 0.080). However, the J 0 vector component was significantly different (p < 0.001). After post hoc analysis, the wavefront aberrometer obtained more positive values for J 0 compared to the other methods. The J 45 component was not significantly different among the three methods (p = 0.143). The mean difference between the wavefront aberrometer and postcycloplegic AR was-0.115 D (LOA,-1.578 to 1.348 D) for M, 0.239 D (LOA,-0.371 to 0.850 D) for J 0 , and-0.015 D (LOA,-0.768 to 0.738 D) for J 45. The mean difference between the wavefront aberrometer and CR was-0.220 D (LOA,-1.790 to 1.350 D) for M, 0.300 D (LOA,-0.526 to 1.127 D) for J 0 , and-0.079 D (-0.662 to 0.504 D) for J 45. Conclusions: The wavefront aberrometer showed good agreement with postcycloplegic AR and CR in spherical equivalents, but tended to produce slightly myopic results. The wavefront aberrometer also overestimated with-the-rule astigmatism. Therefore, we recommend that the device be used for estimations of refractive error, which may be useful for patients who have postural difficulties, live in undeveloped countries, or are bedridden.