Search results for "Photon"
showing 10 items of 3171 documents
Visual quality comparison of conventional and Hole-Visian implantable collamer lens at different degrees of decentering
2013
Purpose To compare the visual quality of implantable collamer lens (ICL) with and without central hole (Hole ICL and conventional ICL) at different degrees of decentering. Methods An adaptive optics visual simulator (crx1, Imagine Eyes, Orsay, France) was used to simulate the –3, –6 and –12 dioptres (D) conventional and Hole ICLs in three conditions: centred and decentred 0.3 and 0.6 mm. Visual acuity (VA) at high-contrast, medium-contrast and low-contrast and contrast sensitivity (CS) were measured in 15 observers for 3 and 4.5 mm pupils. Results No statistically significant differences in VA and CS were found between conventional and Hole ICLs for any ICL powers and pupil sizes evaluated …
Optical and Visual Simulation of Standard and Modified Spherical Aberration Implantable Collamer Lens Post Myopic LASIK Surgery
2013
To evaluate the visual quality achieved in patients undergoing standard or modified implantable Collamer lens (ICL) to correct residual myopic error after laser-assisted in situ keratomileusis (LASIK) surgery.The adaptive optics visual simulator was used to simulate LASIK surgery of moderate and high myopia with a myopic regression corrected by a standard and modified ICL. Visual acuity (VA) and contrast sensitivity (CS) were measured in 14 subjects at 3- and 4.5-mm pupil. Point spread function and simulated retinal images were calculated.Comparing LASIK plus standard ICL and LASIK plus modified ICL simulations, for moderate myopia, VA improvement was less than 1 line in all VA contrasts an…
Image quality and visual performance in the peripheral visual field following photorefractive keratectomy.
2002
ABSTRACT PURPOSE: A theoretical and experimental study was performed to assess the possible effects of photorefractive keratectomy (PRK) on retinal image quality and thresholds in the peripheral visual field. METHODS: Simple optical calculations suggest that although the quality of the retinal image at the fovea of the postoperative PRK eye may be comparable to that in an emmetropic eye, images in the peripheral field may be markedly worse, since peripheral ray bundles may pass partly through ablated and partly through unablated cornea, giving a simultaneous-vision bifocal effect. This would be expected to create an annular zone of confusion, so that light from two different directions in o…
A Passive-Marker-Based Optical System for Computer-Aided Surgery in Otorhinolaryngology: Development and First Clinical Experiences
1999
Objectives: To develop a new type of optical computer-aided surgery (CAS) device that overcomes some of the restrictions of common systems and to examine its accuracy and usability under laboratory and intraoperative conditions. Study Design: Prospective study using laboratory experiments and intraoperative data collection. Methods: An optical CAS system applying passive optical markers for coordinate determination was developed. Laboratory accuracy measurements were obtained on a Plexiglas model with known coordinates of fiducial markers, before and after predefined table movements. Intraoperative accuracy measurements were recorded from 24 patients undergoing endonasal surgery of the para…
Correlates of increased lean muscle mass in women with polycystic ovary syndrome.
2009
ObjectiveMuscle mass plays an important role in determining cardiovascular and metabolic risks in polycystic ovary syndrome (PCOS). In addition, whether lean mass influences carotid intima-media thickness (IMT) in PCOS has not been assessed.DesignProspective investigation.MethodsNinety-five women with PCOS were age- and weight-matched to 90 ovulatory controls. All women had dual X-ray absorptiometry for lean, fat and bone mass, and bone mass density (BMD). Serum testosterone, sex hormone-binding globulin, insulin, and glucose and carotid IMT were determined. Free androgen index (FAI) and insulin resistance (by QUICKI) were calculated.ResultsIn PCOS, waist circumference and insulin were high…
Noninvasive assessment of Crohn's disease activity: a comparison of 18F-fluorodeoxyglucose positron emission tomography, hydromagnetic resonance imag…
2002
Detection of disease activity in Crohn's disease (CD) is of crucial importance for diagnosis and management of the disease. Noninvasive methods for monitoring are desirable and comprise hydromagnetic resonance imaging (hydro-MRI) and leukocyte scintigraphy. In addition, a recent case report indicated the potential of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to assess CD activity. However, comparative prospective studies are lacking.Between February, 1999 and August, 2000, 59 patients with CD were enrolled in a prospective study to assess disease activity by FDG-PET, hydro-MRI, and immunoscintigraphy with anti-nonspecific cross-reacting antigen 95 antigranulocyte antibod…
On-eye optical quality of daily disposable contact lenses for different wearing times
2012
Purpose To quantify the optical quality of various daily disposable contact lenses in vivo and to ascertain its variation in terms of wearing time by means of objective non-invasive determination of wavefront patterns. Methods The crx1 adaptive-optics system was used to measure the wavefront aberrations in 15 myopic eyes before and at 2-h intervals after contact lens fitting, over a 12-h wearing period. Seven types of contact lenses having different material, water content and lens design were evaluated in this study: Dailies Total1, Dailies AquaComfort Plus, Proclear 1 Day, 1-Day Acuvue TruEye, 1-Day Acuvue moist, SofLens daily disposable and Clariti 1-Day. The aberration data were analyse…
Crystalens HD Intraocular Lens Analysis Using an Adaptive Optics Visual Simulator
2013
PURPOSE To compare visual and optical quality of the Crystalens HD intraocular lens (IOL) with that of a monofocal IOL. METHODS The wavefront aberration patterns of the monocular Akreos Adapt AO IOL and the single-optic accommodating Crystalens HD IOL were measured in a model eye. The Crystalens IOL was measured in its nonaccommodative state and then, after flexing the haptic to produce 1.4 mm of movement, in its accommodative state. Using an adaptive optics system, subjects' aberrations were removed and replaced with those of pseudophakes viewing with either lens. Monocular distance visual acuity (DVA) at high (100%), medium (50%), and low (10%) contrast and contrast sensitivity (CS) were …
Role of Octreoscan and Correlation with MR Imaging in Graves' Ophthalmopathy
1995
Since the identification of somatostatin receptors on lymphocytes, orbital infiltration with mononuclear cells in Graves' ophthalmopathy has provided a rationale for receptor imaging with the radiolabeled somatostatin analog Octreotide. In 40 patients with Graves' ophthalmopathy and 10 controls, 110 MBq indium-Octreotide were administered i.v., and scans were performed at 4 and 24 h after injection. An uptake ratio between the orbits and the brain was determined. In 20 ophthalmophathy patients, magnetic resonance imaging (MRI) of the orbits was performed and the T2 relaxation time was measured within the rectus muscles. Compared to controls (4 h Octreotide uptake: median 6.0 counts/pixel/MB…
BMI and an anthropometry-based estimate of fat mass percentage are both valid discriminators of cardiometabolic risk: A comparison with DXA and bioim…
2013
Objective. To determine whether categories of obesity based on BMI and an anthropometry-based estimate of fat mass percentage (FM% equation) have similar discriminative ability for markers of cardiometabolic risk as measurements of FM% by dual-energy X-ray absorptiometry (DXA) or bioimpedance analysis (BIA).Design and Methods. A study of 40–79-year-old male (n=205) and female (n=388) Finns. Weight, height, blood pressure, triacylglycerols, HDL cholesterol, and fasting blood glucose were measured. Body composition was assessed by DXA and BIA and a FM%-equation.Results. For grade 1 hypertension, dyslipidaemia, and impaired fasting glucose >6.1 mmol/L, the categories of obesity as defined b…