Search results for "Ophthalmology"
showing 10 items of 1738 documents
Illusory contours from pictorially three-dimensional inducing elements: counterevidence for Parks and Rock's example.
1993
In 1990 Parks and Rock claimed that, in pictorially three-dimensional (3-D) inducing patterns, an illusory figure does not emerge if a clear occlusion event is not present. A new pictorially 3-D pattern is presented which contradicts this claim. Two experiments were carried out. The first was aimed at ascertaining the presence of an illusory figure in the new 3-D pattern; the second was aimed at offering evidence that in Parks and Rock's pattern the disappearance of the illusory figure could be due to local interferences caused by the line elements in contact with the inducing borders. The results tend to contradict Parks and Rock's conclusions.
Corneal and Refractive Astigmatism in Adults: A Power Vectors Analysis
2009
Purpose. In this article, we examine the relationship between corneal and refractive astigmatism (including with the rule, against-the-rule, and oblique astigmatism) in an adult population using power vectors. Methods. Refractive and keratometric measures of astigmatism were conducted on right eyes of 105 white subjects aged 18 to 59 years. We performed a linear regression of refractive astigmatic error on corneal astigmatism, using the J0 and J45 components of the astigmatism. Results. We obtained a statistically significant regression relationship between the corneal (C) and refractive (R) astigmatism for both J0 and J45 components, namely, RJ0 = 1.07 × CJ0 − 0.28; and RJ45 = 1.46 × CJ45 …
A Slippery Slope: Estimated Slant of Hills Increases with Distance
2014
The slopes of hills tend to be greatly overestimated. Previous studies have found that slope estimates are significantly greater when estimated verbally than with a proprioceptive measure. It has yet to be determined whether these estimates are made for the entire extent of the slope, or whether the estimates in closest proximity are estimated using a different process. Since some parietal cortex neurons respond differently to objects within arm's reach, short-distance slope estimation may utilize these or analogous neurons. Alternatively, greater implied effort might make longer slopes seem steeper. We determined that both verbal and proprioceptive reports of slope are overestimates that …
Curvature of iris profile in spectral domain optical coherence tomography and dependency to refraction, age and pupil size - the MIPH Eye&Health …
2016
Purpose Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the iris. We performed spectral domain OCT examinations in healthy emmetropic, hyperopic and myopic subjects to investigate iris curvature and its associations. Methods In a cross-sectional study, out of 4617 eyes (2309 subjects) those with refractive errors of +3 dioptres were identified by objective refraction. The iris was examined using the anterior segment mode of a spectral domain 3D OCT-2000 (Topcon Inc., Japan) in the temporal meridian, and OCT scans were investigated with respect to presence and amount of convex and concave iris configuration. Ninety-three eyes of 50 s…
Associations of reading posture, gaze angle and reading distance with myopia and myopic progression
2016
Purpose To study the associations of habitual reading posture, gaze angle in reading and reading distance with myopia and changes in myopia among myopic children. Methods A total of 240 myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983–1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were conducted for 237–238 subjects. A further examination was conducted at the mean age of 23.2 years for 178 subjects. Habitual reading posture was elicited by questionnaire at study outset. Reading distance was measured with a Clement Clark accommodometer and gaze angl…
External and internal facial features modulate processing of vertical but not horizontal spatial relations.
2019
Some years ago an asymmetry was reported for the inversion effect for horizontal (H) and vertical (V) relational face manipulations (Goffaux & Rossion, 2007). Subsequent research examined whether a specific disruption of long-range relations underlies the H/V inversion asymmetry (Sekunova & Barton, 2008). Here, we tested how detection of changes in interocular distance (H) and eye height (V) depends on cardinal internal features and external feature surround. Results replicated the H/V inversion asymmetry. Moreover, we found very different face cue dependencies for both change types. Performance and inversion effects did not depend on the presence of other face cues for detecting H changes.…
Contrast sensitivity and glare disability by halogen light after monofocal and multifocal lens implantation
2000
BACKGROUND—Standard examination of contrast sensitivity under conditions of glare disability is performed with incandescent light. A new halogen glare test that simulates glare as seen with oncoming vehicle headlights was used to measure glare disability in patients implanted with multifocal and monofocal intraocular lenses (IOLs). METHODS—28 patients with an average age of 69 years (SD 12 years) were implanted with a monofocal IOL (SI-40NB, Allergan) and 28 patients with an average of 66 years (12 years) were implanted with a refractive multifocal IOL (Array-SA-40N, Allergan). All patients were followed for 5 months postoperatively. Contrast sensitivity at four spatial frequencies (3, 6, 1…
A simple description of age-related changes in crystalline lens thickness.
2010
Purpose An increase in lens thickness is often described as a linear function of age. However, contradictory opinions exist about whether the lens thickness continues to increase after 50 years of age. Differences in slope exist between this increase in younger and older people, but these findings are inconsistent with the linear behavior of an increase in the lens thickness throughout life. We investigated among different functions, including slope variation, which would be the best to show the relation between lens thickness and age. An available model portraying lens growth could be advantageous in many practical applications. The possibility of differences between sexes in lens thicknes…
Effect of age in the ciliary muscle during accommodation: Sectorial analysis
2017
Abstract Purpose To compare changes in the ciliary muscle area at different sectors between pre-presbyopic and presbyopic eyes during accommodation by means of an anterior segment optical coherence tomographer (OCT). Methods The anterior ciliary muscle area was measured in 20 healthy and phakic pre-presbyopic eyes, whose mean age was 23.3 ± 4.4 years, and in 20 healthy and phakic presbyopic eyes, whose mean age was 46.5 ± 5.2 years. The relative change in the cross-sectional area of the ciliary muscle was measured at the nasal, inferior, and temporal sectors between 0 and −3 D of vergence, in −1 D step. A linear model was used to assess the correlation of each eye parameter with the accommo…
Repeatability assessment of biometric measurements with different refractive states and age using a swept-source biometer
2018
Background We aim to assess if refractive error or age may influence the repeatability of measurements using a swept-source biometer. Methods A total of 61 subjects were evaluated with IOLMaster 700 acquiring measurements of axial length (AL), central corneal thickness (CCT), white-to-white distance (WTW), anterior aqueous depth (AQD), lens thickness (LT), and keratometry (K) readings. Repeatability was evaluated classifying the sample according to the refractive state and age by the calculation of the within-subject standard deviation (Sw), coefficient of repeatability, and intraclass correlation coefficient. Results Very similar Sw was acquired among groups for AL, CCT, and WTW. Differenc…