Search results for "Light"

Effects of a 21 days space flight on the mechanical performance and the EMG power spectrum of the leg muscles

2002

Subjective Satisfaction in Long-term Orthokeratology Patients

2013

Purpose: To AU3 evaluate the subjective satisfaction in visual stability, night vision complains, and light distortion phenomena, and also the number of hours and days per week of lens wear, in patients with myopia undergoing orthokeratology (OK) treatment for at least 1 year. Methods: A visual analog scale (VAS) questionnaire containing 18 items was administered to 44 patients, 29 women and 15 men (mean age, 24.39 6 9.11 years), with a baseline spherical equivalent refractive error of 22.40 6 0.94 diopters and astigmatism up to 20.5 diopters. Average treatment period by the time of data collection was 19 6 7 months. Patients rated their satisfaction with the correction, with complaints of …

Light distortion of soft multifocal contact lenses with different pupil size and shape

2020

Purpose: To study the light distortion effects of soft multifocal contact lenses and the influence of different pupil size and shape.Methods: A total of 14 eyes of 7 healthy contact lens users (mean age 28.6 +/- 8.5 years) were recruited. The "Light Disturbance Analyser" device was employed for light characterization. The selected lenses were the monthly disposable "Biofinity multifocal" (CooperVision, CA, USA), both centre-distance and centre-near designs (addition power + 2.50 D). Two circular pupils of 3 mm and 5 mm of diameter, and an elliptical shape (3 horizontal and 5 vertical mm) were used. Metrics such as the light distortion index (LDI), best-fit circle radius and its irregularity…

Enhanced inflammatory and T-helper-1 type responses but suppressed lymphocyte proliferation in patients with seasonal affective disorder and treated …

2015

Abstract Background Animals show seasonal changes in the endocrine and immune system in response to winter stressors. Even though increased inflammation has been implicated in the pathophysiology of depression, whether immune disorder is a key mediator in seasonal affective depression (SAD) is unknown. Here, we hypothesized that short photoperiods in winter may induce inflammatory response, which contributes to SAD, and that light treatments should normalize immune function and improve depressive symptoms. Methods Twenty patients with a diagnosis of SAD, and a score on the HAM-29 of 20 or higher were recruited for this study. Twenty-one healthy subjects with no personal and family history o…

Changes in pattern induced flicker colors are mediated by the blue-yellow opponent process.

1992

The colors of Benham's Top [pattern induced flicker colors (PIFCs)] were matched with color stimuli provided by a computer aided color mixer. Subjects viewed a series of specifically modified black and white disks and matched the resulting subjective color with a comparison field containing the color generated by additive mixing. Different phase relations between the apparently colored ring and the surround were tested. The color loci of all PIFCs were found to lie on a plane in receptor three-space which is given by the axis of the shortwave receptor excitation and a vector given by combining the middle and long wave receptor excitation directions in a fixed ratio of nearly 1:1. From the o…

Electromechanical delay in human skeletal muscle under concentric and eccentric contractions.

1979

In contraction of skeletal muscle a delay exists between the onset of electrical activity and measurable tension. This delay in electromechanical coupling has been stated to be between 30 and 100 ms. Thus, in rapid movements it may be possible for electromyographic (EMG) activity to have terminated before force can be detected. This study was designed to determine the dependence of the EMG-tension delay upon selected initial conditions at the time of muscle activation. The right forearms of 14 subjects were passively oscillated by a motor-driven dynamometer through flexion-extension cycles of 135 deg at an angular velocity of approximately equal to 0.5 rad/s. Upon presentation of a visual s…

Objective measurement of intraocular forward light scatter using Hartmann-Shack spot patterns from clinical aberrometers. Model-eye and human-eye stu…

2007

Purpose To apply software-based image-analysis tools to objectively determine intraocular scatter determined from clinically derived Hartmann-Shack patterns. Setting Aston Academy of Life Sciences, Aston University, Birmingham, United Kingdom, and Department of Optics, University of Valencia, Valencia, Spain. Methods Purpose-designed image-analysis software was used to quantify scatter from centroid patterns obtained using a clinical Hartmann-Shack analyzer (WASCA, Zeiss/Meditec). Three scatter values, as the maximum standard deviation within a lenslet for all lenslets in the pattern, were obtained in 6 model eyes and 10 human eyes. In the model-eye sample, patterns were obtained in 4 sessi…

Surface Lightness Influences Perceived Room Height

2010

Surprisingly little scientific research has been conducted on the effects of colour and lightness on the perception of spaciousness. Practitioners and architects typically suggest that a room's ceiling appears higher when it is painted lighter than the walls, while darker ceilings appear lower. Employing a virtual reality setting, we studied the effects of the lightness of different room surfaces on perceived height in two psychophysical experiments. Observers judged the height of rooms varying in physical height as well as in the lightness of ceiling, floor, and walls. Experiment 1 showed the expected increase of perceived height with increases in ceiling lightness. Unexpectedly, the perce…

Color and lightness constancy in different perceptual tasks

1998

Color and lightness constancy with respect to changing illumination was studied with three different perceptual tasks: ranking of colored papers according (1) to their lightness and (2) to their chromatic similarity in photopic, mesopic, and scotopic states of adaptation, and (3) recognition of remembered colored papers after changes of illumination in photopic vision. Constancy was found in the second task, only. Excitations of light receptors and luminance channels were computed to simulate the empirical rank orders. Results of the first task can be predicted with the hypothesis that luminance channels are activated, if lightness is asked for. Sequences arranged with respect to chromatic …

Effect of luminance on photopic visual acuity in the presence of laser speckle

1988

Visual acuity in coherent and incoherent light has been determined by using square-wave gratings of 100% contrast. Luminance was varied from 3 to 400 cd/m2. Coherent illumination resulted in a 40% loss of visual acuity. This is probably due to the masking effect of coherent spatial noise (speckle). However, the most interesting finding is the change in shape of the photopic visual-acuity-luminance function. With coherent illumination, the function is vertically displaced and of a different gradient. An increase in luminance produces a decrease in visual acuity. This indicates that the masking effect of the speckle is dependent on luminance. Two observers were used, and similar results were …