Search results for "Ophthalmology"
showing 10 items of 1738 documents
In vitro optical performance of nonrotational symmetric and refractive-diffractive aspheric multifocal intraocular lenses: impact of tilt and decentr…
2012
Purpose To evaluate the optical quality of Acrysof Restor SN6AD1 refractive–diffractive +3.00 D and Lentis Mplus LS-312 nonrotational symmetric +3.00 D aspheric multifocal intraocular lenses (IOLs) and analyze the effect of tilt and decentration. Setting University of Valencia, Valencia, and University of Murcia, Murcia, Spain. Design Experimental study. Methods An artificial model eye was used to measure wavefront aberrations of both IOL models. The modulation transfer function (MTF) and point-spread function (PSF) were calculated for a 5.0 mm pupil and under 5 situations: centered, 0.2 mm and 0.4 mm decentered, and 2 degrees and 4 degrees tilted. Results The refractive–diffractive IOL had…
A pilot study on the differences in wavefront aberrations between two ethnic groups of young generally myopic subjects
2008
A comparative population-based cross-sectional study design was used to examine the prevalence of wavefront patterns in two different ethnic groups, and the relationship of these patterns with ocular biometrics and gender. The Shin–Nippon SRW5000 open field autorefractor, the Wavefront Analysis Supported Customized Ablation (WASCA) wavefront analyser and the IOLMaster were used to determine wavefront aberrations, mean spherical equivalent (SE) refractive error and axial length (AL). Seventy-four eyes from 74 young healthy subjects (44 British Asians, 30 Caucasians; 36 men, 38 women; mean age 22.51 ± 3.89 years) with mean SE averaging )1.90 ± 2.76 D (range )10.88 to +2.19 D) were examined. R…
Neural Adaptation to Optical Quality Defects
2010
From an optical perspective the eye is far from perfect. This is a fact that is extensively supported by literature; for instance, Prof. Navarro recently provided us with a fantastic critical review on the various theories behind the different eye models and their flaws.1 The human eye has considerable amounts of higher-order aberrations even when it is emmetropic,2 with great inter-individual variability. Besides, higher-order aberrations are still postulated to have a role in the development of the refractive error, although it is not clear the extent to which this may be (see Charman WN for a review).3 The known optical limitations of the normal human eye raised the question as to what t…
Tolerance to rotation of toric monofocal and bifocal intraocular lenses. A theoretical study
2018
Abstract This manuscript aims to evaluate the tolerance to rotation of a toric monofocal and a toric bifocal intraocular lenses with different cylinder powers. Theoretical designs based on wavefront aberrations were created to simulate a toric monofocal and a toric bifocal intraocular lens. Cylinder power ranged from −1 D to −6 D, in steps of −1 D. Tolerance to rotation was estimated by the visual Strehl ratio based on the optical transfer function (VSOTF) metric. Tolerance to rotation for both monofocal and bifocal intraocular lenses decreased when the cylinder power increased. For the bifocal design studied, the tolerance to rotation was larger for the near focus than for the far, however…
Drifts in real-time partial wavefront correction and how to avoid them
2017
In visual experiments that require real-time partial correction of wavefront aberrations, small errors occur that accumulate over time and lead to drifts in Zernike coefficients of the uncorrected aberrations. A simple algorithm that does not require the inclusion of an additional optical path to obtain independent measurements of the eye's aberrations is described here, and its effectiveness in preventing these drifts is demonstrated.
The tear film and the optical quality of the eye
2010
The stability of the tear film plays an important role in the optical quality of the eye. Various methods have been developed to quantify the contribution of the tear film to optical quality, including the double-pass optical method, Hartmann-Shack wavefront sensing, videokeratoscopy, retroillumination analysis, and interferometry. In addition to assessing the effect of tear film irregularities, these methods can aid in the diagnosis of dry-eye related conditions and the monitoring of therapy. This review describes the methodologies used to assess the relationship between the tear film and optical quality of the eye and summarizes the most important findings obtained with these methods with…
Pattern Dystrophy of the Macula in a Case of Steinert Disease
2013
<b><i>Introduction:</i></b> Myotonic dystrophies are typically associated with ocular complications like ptosis, weakness of the ocular muscle and cataracts, but also with less recognized retinal changes. <b><i>Case Report:</i></b> A 41-year-old female with type 1 myotonic dystrophy complained of progressive vision loss. Slit lamp examination revealed the presence of typical bilateral polychromatic cataract with posterior subcapsular component. Dilated fundus examination was remarkable for bilateral macular depigmented changes. Multimodal imaging analysis of the macula suggested the presence of a butterfly-shaped pattern dystrophy. <b>&l…
Device interchangeability on anterior chamber depth and white-to-white measurements: a thorough literature review
2016
We have reviewed a set of recently published studies that compared the anterior chamber depth (ACD) and/or white-to-white (WTW) distance obtained by means of different measuring devices. Since some of those studies reached contradictory conclusions regarding device interchangeability, this review was carried out in attempting to clarify which clinical devices can or cannot be considered as interchangeable in clinical practice to measure ACD and/or WTW distance, among these devices: A-scan, ultrasound biomicroscopy, Orbscan and Orbscan II (Bausch&Lomb Surgical Inc., San Dimas, California, USA), Pentacam and Pentacam HR (Oculus, Wetzlar, Germany), Galilei (Ziemer, Switzerland), Visante optica…
Neurophysiologic Testing in Infants With Usher Syndrome Type 1
2009
Purpose: Usher syndrome type 1 needs to be diagnosed at early age, when speech therapy and cochlear implantation can stimulate communication in a deaf child who will confront an additional visual handicap. Molecular diagnosis is not routinely available. Visual function tests are not easily performed in young children. Before the age of six years, progressive retinal degeneration does not always show fundoscopic changes and few data are available regarding neurophysiologic abnormalities. This study was designed to describe electroretinogram (ERG) and visual evoked potentials (VEP) in a series of fourteen children with Usher syndrome type I.Methods: Monocular ERG and binocular VEP were perfor…
Plasma omega 3 polyunsaturated fatty acids and macular pigment optical density in subjects at high risk for age-related macular degeneration: the Lim…
2016
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.; Purpose: In numerous epidemiological studies, omega 3 polyunsaturated fatty acids (PUFAs) have been associated with a decreased risk of age-related macular degeneration (AMD). Beyond their structural, functional and neuroprotective roles, omega 3 PUFAs may favor the retinal accumulation of lutein and zeaxanthin and thus increase macular pigment optical density (MPOD). We examined the associations of MPOD with plasma omega 3 PUFAs in subjects with at least one parent affected by neovascular AMD. Methods: The Limpia study is a double-blind, placebo controlled, prospective randomize…