Search results for " Lens"

Compression forces of haptics of selected posterior chamber lenses

1997

Abstract Purpose: To compare the compressive forces of the haptics of different intraocular lens (IOL) models and analyze the observed differences. Setting: Central Hospital of Central Finland and University of Jyvaskyla, Jyvaskyla, Finland. Methods: The haptics of 28 IOL models were compressed to a diameter of 9.0 mm. The compression forces were measured at 0.5 mm intervals. The conclusions were verified by numerical simulations of mechanical models of the lenses. Results: The measured forces varied between 100 and 601 mg at a diameter of 11.0 mm, 206 and 1057 mg at a diameter of 10.0 mm, and 315 and 2094 mg at a diameter of 9.0 mm. The slopes of the force curves of the three-piece lenses …

Compression forces of haptics of freely rotating posterior chamber intraocular lenses.

1998

Abstract Purpose: To measure the compressive forces of the haptics of 28 intraocular lens (IOL) models for different modes of compression and compare the results of two types of measurements. Setting: Department of Ophthalmology, Central Hospital of Central Finland, Jyvaskyla, Finland. Methods: The haptics of 28 types of IOLs were compressed to a diameter of 9.0 mm between curved anvils. The compression forces in the plane of compression (i.e., in the plane of the optics) were measured at 0.5 mm intervals. During compression, the optics and the haptics were free to rotate with respect to the anvils. The results were compared with those of earlier measurements in which the optics were held f…

Effect of Decentration on the Optical Quality of Two Intraocular Lenses

2016

To analyze the effect of decentration on the optical quality of two diffractive-refractive intraocular lenses, a bifocal and a trifocal, when displaced laterally (horizontal direction) from the center.The AT LISA 809M IOL (+3.75 D add) with two main foci and the AT LISA tri 839MP intraocular lens with three main foci (Carl Zeiss Meditec AG, Jena, Germany) were analyzed. The optical quality of the intraocular lenses was measured with the PMTF (power and modulation transfer function [MTF] measurement for refractive and diffractive intraocular lenses) optical bench (Lambda-X, Nivelles, Belgium). The optical quality of the lenses was evaluated by the MTF at different object vergences, the avera…

Agreement of predicted intraocular lens power using swept-source optical coherence tomography and partial coherence interferometry

2021

PURPOSE To analyze the agreement of the predicted intraocular lens (IOL) power obtained with ANTERION, IOLMaster 700 and Pentacam AXL biometers. METHODS We calculated the monofocal and trifocal IOL power using the SRK/T, Haigis, Barrett Universal II and Hoffer Q formulas for 106 eyes. IOL power agreement between devices was evaluated using the Bland-Altman method. RESULTS We found significant differences between biometers comparisons (p  0.05), with the same outcomes for medium- and long-eyes. No significant differences were found using the SRK/T, Haigis, or Hoffer Q formulas for short-eyes (p > 0.1). However, Barrett Universal II formula produced significant differences (p < 0.05) and thes…

Optical Quality Comparison between Spherical and Aspheric Toric Intraocular Lenses

2014

Purpose To measure and compare the optical quality of spherical and aspheric toric intraocular lenses (IOLs). Methods Wavefront aberrations of AcrySof Toric and IQ Toric IOLs (Alcon Laboratories) for different powers were measured at 3- and 5-mm pupils by Nimo TR0805 instrument. The Zernike coefficients of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were evaluated. The point spread functions (PSFs) of each IOL evaluated were calculated from the wavefront aberrations. The PSF images also were calculated from the IOL wavefront aberrations, adding the cornea's aberrations to simulate the optical quality after their implantation. Results Spherical toric IOLs showed…

A rapid method for measuring intraocular lens power in vitro with a focimeter.

2015

In this paper we describe a new method for measuring the intraocular lens (IOL) power using a focimeter, a negative ophthalmic lens and a saline solution (0.9% NaCl). To test this we measured the power of 58 different IOLs and we compared them with the power stated by the manufacturer. Despite the limitations, the results show a good correlation.

Incisional Keratotomy to Toric Intraocular Lenses: An Overview of the Correction of Astigmatism in Cataract and Refractive Surgery

2003

Impact of contact lens material and design on the ocular surface.

2018

BACKGROUND: To evaluate the impact on the ocular surface of a daily disposable hydrogel contact lens with high water content compared with two silicone hydrogel daily disposable lenses of lower water content. METHODS: The hydrogel lens assessed was made from nesofilcon A and the silicone hydrogel lenses were made of delefilcon A and stenfilcon A. Contact lens thickness was measured to assess material stability during daily wear, and ocular surface parameters such as tear film osmolarity, tear meniscus area and central corneal thickness were also assessed. Optical quality was analysed for all cases by means of wavefront aberrometry. RESULTS: The nesofilcon A was shown to be the thinnest lens…

Light transmission and ultraviolet protection of contact lenses under artificial illumination

2016

Purpose: To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)). Methods: The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer. Results: Five of the nine soft CLs analysed state that they incorporate UV filters…

Rileggere l'identità. L'operazione Louvre Lens nel Nord Pas de Calais

2015

Il paper propone una lettura del progetto per il Louvre a Lens alla luce del tema locale/globale, tentando di rintracciare la dimensione identitaria presente all'interno di un progetto che si rivolge, per sua natura, all'attenzione mondiale. Il testo analizza i processi che hanno permesso al progetto di essere appoggiato dalla popolazione locale, per il suo porsi come opportunità di sviluppo economico e sociale e per la sua capacità di rileggere, attraverso il linguaggio contemporaneo, i caratteri del paesaggio minerario francese.