Search results for "Optical quality"
showing 10 items of 30 documents
Optical quality of rotationally symmetrical contact lenses derived from their power profiles.
2017
To present a methodology for evaluating the optical quality of rotationally symmetrical contact lenses (CLs) from a single power profile.Simulated rotationally symmetrical power profiles corresponding to different CLs designs (monofocal, two-zone center-near bifocal, and four-zone center-distance bifocal) were used to calculate the wavefront error profile by means of numerical integration. Then, each lens wavefront error profile was spun around the center to obtain the lens wavefront error surface. From the surface, monochromatic optical transfer functions (OTF), simulated images and the visual Strehl ratio based on the OTF (VSOTF) were obtained for different distances and pupil sizes (3 an…
In vitro optical quality comparison of 2 trifocal intraocular lenses and 1 progressive multifocal intraocular lens.
2015
Purpose To evaluate the optical quality of 3 multifocal intraocular lenses (IOLs): the Mini Well Ready progressive multifocal aspheric IOL, the AT LISA trifocal diffractive IOL, and the Finevision full diffractive trifocal IOL. Setting University of Valencia, Valencia, Spain. Design Experimental study. Methods An instrument designed for measuring real-time modulation transfer function (MTF) and IOL power was used to measure the optical quality of each IOL for 3.0 mm and 4.5 mm apertures. This instrument measures both sagittal and tangential MTFs. The optical quality of each IOL was evaluated with the MTF, through-focus MTF, defocus tolerance, Strehl ratio MTF, and relative percentage of lig…
Assessing the in vitro optical quality of presbyopic solutions based on the axial modulation transfer function.
2016
Purpose To present a metric for assessing the in vitro optical quality of rotationally symmetrical optical elements based on volume calculation under the surface defined by the axial modulation transfer function (MTF). Setting University of Valencia, Valencia, Spain. Design Experimental study. Methods The metric volume under the axial MTF was used to assess the optical quality of 2 rotationally symmetrical multifocal intraocular lenses (IOLs) within various defocus intervals (0.50 diopter [D], 0.75 D, and 1.00 D) and at various spatial frequency intervals (7.5 cycles per degree [cpd], 15.0 cpd, and 30.0 cpd). Results The far focus of the bifocal IOL yielded higher volume values at all spati…
Modulation transfer function: Rigid versus foldable phakic intraocular lenses
2008
Purpose To study in a standard eye model the changes in modulation transfer function (MTF) of a monofocal intraocular lens (IOL) when a phakic IOL (pIOL) is placed in the anterior chamber, compare the MTFs of the rigid Artisan pIOL and foldable Artiflex pIOL, and evaluate the temporal evolution of the MTF of the foldable pIOL after the mechanical stress the pIOL undergoes when injected. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods The MTF values of the IOLs were calculated from the cross-line spread function recorded with the Opal Vector System. The measurements were taken using an eye model following the British and EN-ISO standards with 2.0 mm, 3.0 mm, 4.0 mm…
The posterior chamber phakic refractive lens (PRL): a review
2012
Implantation of phakic intraocular lenses (pIOLs) is a reversible refractive procedure, preserving the patient’s accommodative function with minimal induction of higher order aberrations compared with corneal photoablative procedures. Despite this, as an intraocular procedure, it has potential risks such as cataracts, chronic uveitis, pupil ovalization, corneal endothelial cell loss, pigmentary dispersion syndrome, pupillary block glaucoma, astigmatism, or endophthalmitis. Currently, only two models of posterior chamber pIOLs are commercially available, the implantable collammer lens (STAAR Surgical Co.) and the phakic refractive lens (PRL; Zeiss Meditec). The number of published reports on…
In vitro optical quality differences between multifocal apodized diffractive intraocular lenses.
2013
Purpose To compare the in vitro optical quality of multifocal apodized intraocular lenses (IOLs) at different focal points. Setting University of Valencia, Valencia, Spain. Design Experimental study. Methods The Acrysof Restor +3.0 diopter (D) multifocal IOL with 2 main foci (bifocal IOL) and the Finevision multifocal IOL with 3 main foci (trifocal IOL) were evaluated. The optical quality was quantified using the modulation transfer function (MTF) at 7 focal points and for 3.0 mm and 4.5 mm apertures. The through-focus MTF at 10 focal points of the IOLs was also recorded. Results For the 0.0 D and −2.5 D focal points, the bifocal IOL showed the highest MTF values for pupil sizes as well as …
Modulation transfer function of a toric intraocular lens: evaluation of the changes produced by rotation and tilt.
2011
PURPOSE: To evaluate the changes in optical quality when toric intraocular lenses (IOL) are rotated or tilted and to demonstrate that IOL rotation produces an increasing effect of aberrations. METHODS: Modulation transfer function (MTF) and average modulation were used to analyze the image quality of a toric IOL. The axis of the toric IOL was rotated 5°, 10°, 15°, 20°, 25°, and 30° in successive MTF measurements. The tilt values were 0° to 5°, in increments of 1°, plus a tilt of 15°. Pupil diameters of 3 and 5 mm were used. RESULTS: The MTF decay due to aberrations was more sensitive to rotation than tilt. The main decrement in the average modulation, of approximately 50% in both pupils, o…
Contact lenses: do they really change the opticalperformance?
1996
Abstract In this investigation the quality of two types of optical correction, hydrogel contact lenses and ophthalmic lenses, wascompared by measuring the modulation transferfunction (MTF) of the correcting lens plus visual optics system using an objective method. A merit function was defined in order to allow the direct comparison between the optical performance with the two corrections. A study on 10 subjects was undertaken, measuring the MTF of both corrections by using the double pass method. The results show that the optical quality of contact lenses was higher than that with ophthalmic lenses. The contrast sensitivity function (CSF) and visual acuity (VA) were determined as subjective…
Phake Intraokularlinsen
2004
Phakic intraocular lenses (PIOLs), which are located closer to the eye's nodal points than the anterior corneal surface, can provide superior optical quality for higher corrections because of retention of normal prolate corneal asphericity and larger effective optical zones. Improvements in the material and design of phakic intraocular lenses and their insertion devices combined with advances in the understanding of the anatomical and physiological interactions of the PIOLs with intraocular structures, have increased safety and efficacy. Safety of these implants over the long term remains a concern, but in several situations PIOLs are the refractive correction of choice. The purpose of this…
Keratoconus apex positions impact on visual acuity and contrast sensitivity
2020
The change of corneal shape in keratoconus subjects can impact the optical quality of the eye on the retina and it reduces the contrast sensitivity by light scattering. The aim of our study was to estimate the keratoconus subjects’ contrast sensitivity and visual acuity depending on keratoconus apex position. We included 45 keratoconus subjects (77 eyes), which have keratoconus in the first to the third stage, in our study. There were 33 eyes with keratoconus apex in the central part of the cornea and 46 eyes with keratoconus apex in the periphery of the cornea. Contrast sensitivity and visual acuity were measured at 3 m with and without the best possible spectacle correction using the FrAC…