Search results for "Ophthalmology"
showing 10 items of 1738 documents
A comparison of the Canon TX-20P™ non-contact tonometer and pachymeter in healthy eyes
2012
Background: The aim of this study was to compare the intraocular pressure (IOP) and the central corneal thickness (CCT) measurements obtained with the Canon TX-20P™ with IOP measured with Goldmann applanation tonometer (GAT) and the CCT measured with ultrasound (US) pachymetry in healthy eyes. Methods: Thirty one healthy voluntary subjects participated in the study, age ranging from 16 to 81 years (mean age 50.9 years). In total 58 eyes were selected for analysis. All measurements were performed by the same examiner. The measurements were taken in the same order in all subjects: Canon IOP and CCT, Goldmann IOP and US CCT. Results: A strong correlation was found between IOP for both CCT comp…
New Objective Refraction Metric Based on Sphere Fitting to the Wavefront
2017
Purpose. To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes.Methods. A sphere is fitted to the ocular wavefront at the center and at a variable distance,t. The optimal fitting distance,topt, is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius,r0, and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes.Results. For pupil radiir0≤2 mm, the new metric predicts the equ…
Intraocular Telescopic System Design: Optical and Visual Simulation in a Human Eye Model
2016
Purpose. To design an intraocular telescopic system (ITS) for magnifying retinal image and to simulate its optical and visual performance after implantation in a human eye model. Methods. Design and simulation were carried out with a ray-tracing and optical design software. Two different ITS were designed, and their visual performance was simulated using the Liou-Brennan eye model. The difference between the ITS was their lenses’ placement in the eye model and their powers. Ray tracing in both centered and decentered situations was carried out for both ITS while visual Strehl ratio (VSOTF) was computed using custom-made MATLAB code. Results. The results show that between 0.4 and 0.8 mm of d…
Optical Evaluation of New Designs of Multifocal Diffractive Corneal Inlays
2019
[EN] Purpose. To assess the imaging properties of two different designs of a new concept of corneal inlays whose working principle is based on diffraction. Methods. The quality of the retinal images provided by Diffractive Corneal Inlays (DCIs) was evaluated theoretically in comparison with Small Aperture Corneal Inlay (SACI). ZEMAX OpticStudio software was employed for the simulations in an eye model with different pupil diameters (3.0 mm and 4.5 mm). The employed merit functions in the analysis were the Modulation Transfer Function (MTF), the area under the MTF (MTFa), and the Point Spread Function (PSF). Comparison was made with the SACI at different defocus conditions. Results. The bifo…
Image quality with multifocal intraocular lenses and the effect of pupil size
2007
Purpose To analyze the image quality with a refractive and 2 hybrid refractive–diffractive multifocal intraocular lenses (IOLs) in vitro to determine the IOL modulation transfer function (MTF) following the EN-ISO international standard for distance and near vision and to study the IOLs' behavior with different pupil sizes. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods This study evaluated 4 IOLs: the hybrid refractive–diffractive AcrySof ReSTOR SN60D3 (Alcon) and Tecnis ZM900 (AMO), the refractive ReZoom NXG (AMO), and the monofocal AcrySof SN60WF (Alcon). The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Sci…
Imaging Quality of Bifocal Piggyback Intraocular Lens versus ReSTOR and TECNIS Multifocal Lenses
2009
Purpose The imaging quality provided by a piggyback integrated by a monofocal intraocular lens (IOL) + a bifocal IOL of zero power and +3.75 diopters of addition is compared with the optics quality of a simple multifocal IOL of the same power and addition. Methods The imaging quality was evaluated by determining the modulation transfer function (MTF), using an artificial eye simulating in vivo conditions of the anterior chamber, including an artificial cornea and a wet cell containing physiologic solution where the IOL was positioned. The MTFs of the bifocal piggyback for near and distance vision were measured, with pupil diameters of 3 and 5 mm, and compared with the MTFs of an equivalent …
Prevalence and Time Trends in Myopia Among Children and Adolescents.
2020
Background Myopia (near-sightedness) is increasing worldwide, especially in Asia. The aim of this study was to describe trends in the prevalence of myopia in Germany. Methods We analyzed data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS; baseline survey 2003-2006, N = 17 640; wave 2, 2014-2017, N = 15 023). The presence of myopia was determined from a parent questionnaire and validated by the use of a visual aid. The population prevalence of myopia was calculated. Based on the KiGGS wave 2 data, potential risk factors for myopia were identified by means of logistic regression. Results The prevalence of myopia at the age of 0-17 years in Germany…
Uveal effusion syndrome complicated by anterior ischemic optic neuropathy
1995
We report on a case of idiopathic uveal effusion syndrome complicated by AION. To our knowledge such an association hasn't been previously described. We suggest that scleral thickening caused obstruction of vortex veins followed by uveal effusion and compression of posterior ciliary arteries within their intrascleral tract, leading to AION. Nevertheless it can't be excluded that AION was the result of mechanical compression on ciliary vessels of optic disc by choroidal detachment. © 1996, Kluwer Academic Publishers. All rights reserved.
Judging body weight from faces: the height-weight illusion.
2012
Being able to exploit features of the human face to predict health and fitness can serve as an evolutionary advantage. Surface features such as facial symmetry, averageness, and skin colour are known to influence attractiveness. We sought to determine whether observers are able to extract more complex features, namely body weight. If possible, it could be used as a predictor for health and fitness. For instance, facial adiposity could be taken to indicate a cardiovascular challenge or proneness to infections. Observers seem to be able to glean body weight information from frontal views of a face. Is weight estimation robust across different viewing angles? We showed that participants stron…
Functional and biomechanical changes in keratoconic corneas after implantation of intracorneal ring segments 5 and 6mm in diameter
2012
Purpose To determinate biomechanical and functional changes in human keratoconic corneas after triangular section ring implantation in two designs. Methods Retrospective study of biomechanical properties of 46 patients (60 eyes) with keratoconus undergoing surgery Keraring® intracorneal ring segments divided into two groups according to 5 or 6 mm of diameter. Surgical technique to made the channel was with IntraLase femtosecond laser. UCVA and BSCVA were measured and biomechanical factors provided by the device ORA before surgery and postoperatively one month, 3 months and 6 months. Results After surgery, we obtained a significant increase (p 0.05). At baseline- 6 months, the improvement in…