Search results for "Wavefront"
showing 10 items of 124 documents
Visual quality with corneo-scleral contact lenses after intracorneal ring segment (ICRS) implantation for keratoconus management
2019
Purpose: To evaluate the visual quality results when fitting a corneo-scleral contact lens (CScL) after intracorneal ring segment (ICRS) implantation for keratoconus management. Methods: Twenty-seven eyes of 27 patients with keratoconus underwent ICRS implantation and had CScL fitted as their visual quality was unsatisfactory with their spectacles or contact lenses. Patients received a complete eye examination, refraction and visual acuity assessment, anterior eye biomicroscopy, ocular fundus examination, corneal topographic analysis, endothelial-cell count, and visual quality assessment using contrast sensitivity and aberrometry tests. A diagnostic trial set was used in the fitting process…
Corneal Aberrations in Former Preterm Infants: Results From The Wiesbaden Prematurity Study
2017
Purpose To compare corneal aberrations in former preterm infants to that of full-term infants. Methods A prospective cross-sectional study was carried out measuring the corneal shape with Scheimpflug imaging in former preterm infants of gestational age (GA) ≤32 weeks and full-term infants with GA ≥37 weeks now being aged between 4 to 10 years. The main outcome measures were corneal aberrations including astigmatism (Zernike: Z2-2; Z22), coma (Z3-1; Z31), trefoil (Z3-3; Z33), spherical aberration (Z40) and root-mean square of higher-order aberrations (RMS HOA). Multivariable analysis was performed to assess independent associations of gestational age groups and of retinopathy of prematurity …
Visual and optical performance with the ReZoom multifocal intraocular lens
2011
Purpose This study evaluated visual acuity, contrast sensitivity, and wavefront aberrations after refractive multifocal intraocular lens (IOL) implantation. Methods A prospective study comprising 174 eyes of 87 patients who had bilateral implantation of a multifocal IOL was carried out. A control group of 100 eyes of 50 age-matched patients with a monofocal IOL was used for comparison. Uncorrected and corrected distance and near visual acuity, contrast sensitivity (CS), and wavefront analysis (Hartmann-Shack) was performed 6 months after surgery. Contrast sensitivity was tested for distance and near under mesopic (2 cd/m2) and photopic conditions (90 cd/m2). Results Distance photopic CS was…
Optical quality after instillation of eyedrops in dry-eye syndrome
2010
Purpose To study the effect of eyedrop instillation on the optical quality of the air–tear film interface at the anterior cornea in cases of dry eye. Setting University of Valencia, Valencia, Spain. Methods Corneal aberrations (total, spherical-like, and coma-like) were determined from corneal elevation maps and purpose-designed software in cases of dry eye before, immediately after, and 10 minutes after lubricating eyedrop instillation (Blink Intensive Tears). All data were decomposed using Zernike polynomials to yield the root-mean-square wavefront deviations for pupil diameters of 3.0 mm and 5.5 mm. Outcome measures included comparison with clinical tear breakup time (TBUT). Results Wave…
Corneo-scleral contact lenses in an uncommon case of keratoconus with high hyperopia and astigmatism
2017
Purpose: To analyse the visual quality achieved by fitting corneo-scleral contact lenses (CScL) in an uncommon case of bilateral keratoconus, high hyperopia and astigmatism. Methods: A 45-year-old man presented for eye examination due to the unsatisfactory quality of his vision wearing soft toric contact lenses. He presented high hyperopia and astigmatism with bilateral keratoconus. He was fitted with CScL to correct his irregular astigmatism and ocular aberrations. A diagnostic trial set was used in the fitting process and he was assessed according to standardised fitting methodology. Visual acuity, corneal topography, biometry and ocular aberrations were evaluated. The follow-up period wa…
Reduction of spherical-aberration impact in microscopy by wavefront coding
2009
In modern high-NA optical scanning instruments, like scanning microscopes, the refractive-index mismatch between the sample and the immersion medium introduces a significant amount of spherical aberration when imaging deep inside the specimen, spreading out the impulse response. Since such aberration depends on the focalization depth, it is not possible to achieve a static global compensation for the whole 3D sample in scanning microscopy. Therefore a depth-variant impulse response is generated. Consequently, the design of pupil elements that increase the tolerance to this aberration is of great interest. In this paper we report a hybrid technique that provides a focal spot that remains alm…
Changes in the objective amplitude of accommodation with pupil size.
2014
PURPOSE We evaluate the effect of pupil size on objectively measured amplitude of accommodation (AA). METHODS Pupil diameter and wavefront aberrometry were obtained in 15 eyes when stimulus swept across the range of clear vision in steps of 0.5 diopters. Wavefront refraction techniques were used to compute objective AA as the maximum refractive change. Measurements were obtained monocularly under low and high ambient room lighting conditions with a fixed luminance of the fixation target. Amplitude of accommodation computations were performed taking into account just paraxial rays (paraxial AA) or including the effects of the change of spherical aberration during accommodation (minRMS AA). R…
Single-shot digital holography by use of the fractional Talbot effect
2009
We present a method for recording in-line single-shot digital holograms based on the fractional Talbot effect. In our system, an image sensor records the interference between the light field scattered by the object and a properly codified parallel reference beam. A simple binary two-dimensional periodic grating is used to codify the reference beam generating a periodic three-step phase distribution over the sensor plane by fractional Talbot effect. This provides a method to perform single-shot phase-shifting interferometry at frame rates only limited by the sensor capabilities. Our technique is well adapted for dynamic wavefront sensing applications. Images of the object are digitally recon…
Optical Quality Comparison of Conventional and Hole-Visian Implantable Collamer Lens at Different Degrees of Decentering
2012
To compare the optical quality of implantable Collamer lens (ICL) with and without central hole (Hole ICL and conventional ICL) at different degrees of decentering.Experimental laboratory investigation.Wavefront aberrations of the -3, -6, and -12 diopter (D) V4b and -3, -6, and -12 D V4c ICLs were measured in 3 conditions-centered and decentered 0.3 and 0.6 mm-at 3-mm and 4.5-mm pupils. The root mean square of total higher order aberrations, trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were evaluated. In addition, point spread function and simulated retinal images of ICLs were calculated from the wavefront aberrations for each ICL and all conditions of decenteri…
Focal squeeze in axicons
2005
The on-axis irradiance distribution of a truncated conical wavefront is evaluated in terms of the Fresnel number of the focusing geometry. In agreement with geometrical optics, a focal line of increasing intensity is generated for extremely high Fresnel numbers. Otherwise clear deviations may be observed for the position of the maximum irradiance along the optical axis. A remarkable focal squeeze appears and, for decreasing Fresnel numbers, this effect manifests stronger. An analytical formula is provided for the fast evaluation of the focal squeeze.