Search results for "Ophthalmology"
showing 10 items of 1738 documents
Synergy of spatial frequency and orientation bandwidth in texture segregation
2021
Defining target textures by increased bandwidths in spatial frequency and orientation, we observed strong cue combination effects in a combined texture figure detection and discrimination task. Performance for double-cue targets was better than predicted by independent processing of either cue and even better than predicted from linear cue integration. Application of a texture-processing model revealed that the oversummative cue combination effect is captured by calculating a low-level summary statistic (\(\Delta CE_m\)), which describes the differential contrast energy to target and reference textures, from multiple scales and orientations, and integrating this statistic across channels wi…
Optical coherence tomography of chorioretinal and choroidal folds
2007
. Purpose: To report the optical coherence tomography (OCT) findings in cases of chorioretinal and choroidal folds. Methods: Eight subjects with folds of the fundus of the eye were examined with fundus photography, fluorescein angiography, B-scan ultrasonography and Stratus OCT. Results: Two types patterns were found on OCT. Five cases showed undulating retinal as well as retinal pigment epithelial lines of normal thickness; these were defined as chorioretinal folds. The posterior vitreous surface often adhered to the crests of the folds only. Three cases exhibited a wavy appearance of the retinal pigment epithelium and a flat retinal surface; these were classified as choroidal folds. Co…
Tear film stability over a myopia control contact lens compared to a monofocal design
2021
Background: To compare the short-term effect of two contact lenses on pre-lens tear film stability and comfort: dual-focus contact lens (MiSight) and a monofocal contact lens (Proclear 1-day).Methods: This randomised, double-masked, crossover study was performed in twenty-eight healthy, myopic volunteers aged between 18 and 32 years (23.5 +/- 4.1 years). Only one randomly chosen eye was assessed. Distance vision and refraction were evaluated at baseline. Each contact lens type (monofocal and dual-focus) was randomly fitted, always in both eyes. A visual analogue scale between 0 and 10 was used to assess general comfort, physical comfort, and visual comfort. Tear Film Surface Quality (TFSQ) …
Spectral transmission of the pig lens: Effect of ultraviolet A+B radiation
2014
Summary Objective To determine the spectral transmission curve of the crystalline lens of the pig. To analyse how this curve changes when the crystalline lens is irradiated with ultraviolet A + B radiation similar to that of the sun. To compare these results with literature data from the human crystalline lens. Procedures We used crystalline lenses of the common pig from a slaughterhouse, i.e. genetically similar pigs, fed with the same diet, and slaughtered at six months old. Spectral transmission was measured with a Perkin-Elmer Lambda 35 UV/VIS spectrometer. The lenses were irradiated using an Asahi Spectra Lax-C100 ultraviolet source, which made it possible to select the spectral emissi…
Light scattering in artificial fog and simulated with light scattering filter.
2009
Disability glare, affecting e.g. road safety at night, may result either from intraocular light scattering or from external conditions such as fog. Measurements were made of light scattering in fog and compared with intraocular straylight data for normal eyes and eyes with simulated cataract. All measurements were made with a direct compensation flicker method. To estimate light scattering levels in fog, straylight measurements were carried in a fog chamber for different densities of fog. Density was characterized by the meteorological term visibility V and ranged from 7 to 25. Test distance for measurements in the fog was constant at 5 m. Cataract eye conditions were simulated by placing a…
Optical and Visual Quality of the Visian Implantable Collamer Lens Using an Adaptive-Optics Visual Simulator
2013
To evaluate visual and optical quality of the implantable collamer lens for different powers and sizes of incision surgery.Prospective study in humans.An adaptive optics visual simulator was used to measure 3 powers of implantable collamer lenses and simulate the implantable collamer lens wavefront aberration's pattern for small- and large-incision surgery. Visual acuity (VA) and contrast sensitivity were measured in 11 observers for 3- and 5-mm pupils. Modulation transfer function, point spread function, and Strehl ratio were calculated.At 3 mm pupil, no statistically significant differences were found between both incision sizes for any implantable collamer lens power, except for -15 diop…
The effect of spherical aberration on visual performance and refractive state for stimuli and tasks typical of night viewing
2018
Purpose: The aim of this work was to examine the impact of Seidel spherical aberration (SA) on optimum refractive state for detecting and discriminating small bright lights on a dark background. Methods: An adaptive-optics system was used to correct ocular aberrations of cyclopleged eyes and then systematically introduce five levels of Seidel SA for a 7-mm diameter pupil: 0, ± 0.18, and ± 0.36 diopters (D) mm−2. For each level of SA, subjects were required to detect one or resolve two points of light (0.54 arc min diameter) on a dark background. Refractive error was measured by adjusting stimulus vergence to minimize detection and resolution thresholds. Two other novel focusing tasks for si…
Multilayer amniotic membrane transplantation in severe ocular graft versus host disease
2001
To clarify the usefulness of multilayer amniotic membrane transplantation in an unusual case of calcareous corneal degeneration in a patient with graft-versus-host disease.A 20-year-old Caucasian woman had bilateral calcareous corneal degeneration of one year of evolution, secondary to graft-versus-host disease. Treatment for both eyes with topical steroids and antibiotic ointment was not successful. Right eye had a spontaneous corneal perforation, and a three-layer circle amniotic membrane graft was applied to the whole cornea.During a follow-up period of 20 months we observed stability of the corneal epithelium and stroma. The amniotic membrane-covered area showed rapid epithelization, re…
Electrophysiological findings of neuronal ceroid lipofuscinosis in heterozygotes.
1988
Nineteen obligate heterozygotes, 8 individuals at risk of being heterozygote, and 10 patients afflicted with four different forms of neuronal ceroid lipofuscinosis were examined electrophysiologically. The group of obligate heterozygotes was compared to age-matched control groups. Statistically significant differences were found between scotopic b-wave amplitudes, P-ERG amplitudes, and EOG light peaks of the obligate carriers of the juvenile type and the control subjects. The photopic L-ERGs and the latencies of the VEPs were mostly within the normal range. The findings represent the first evidence of functional ophthalmological changes in obligate carriers of neuronal ceroid lipofuscinosis…
Congenital hypertrophy of the retinal pigment epithelium and familial polyposis of the colon.
1987
Inquiries to Manuel Diaz Llopis, M.D., Cl Cirilo Amoros No. 1 PTA 2, Valencia 46004, Spain. Familial polyposis of the colon is a dominant autosomal disorder that is characterized by hundreds and sometimes thousands of adenomatous polyps throughout the entire colon, which begin in adolescence. Virtually all pa tients with familial polyposis develop carcino ma of the colon by age 50 years. A total colectomy should be carried out early in adult life in affected persons. Because of the autosomal dominant inheritance pattern, an intensive sur vey of family members must be conducted. There is no phenotype biochemical abnormality or serologic marker that indicates whether a familial member will…