Search results for "contrast sensitivity"

Surgical management of subfoveal choroidal neovascular membranes in age-related macular degeneration by macular relocation: experiences of an early-s…

2009

The MARAN (Macular Relocation in Age-related Neovascular disease) trial was planned to assess the effectiveness of full macular relocation (MR) in patients with neovascular age-related macular degeneration (AMD).Randomised, prospective, controlled clinical trial.Patients suffering from visual loss because of AMD were randomised to either surgery or a control group receiving standard treatment (observation or photodynamic therapy (PDT)). The primary end point was the change of visual acuity (VA) (ETDRS) 52 weeks after randomisation compared with initial VA, and secondary end points included reading performance, contrast sensitivity, stability of fixation, eye-specific quality of life, and th…

Effect of Color on Contrast Sensitivity with Two Different Accommodative Stimuli

1993

We studied the influence of color and accommodation on the contrast sensitivity function (CSF). At the same time, we measured the effect of axial chromatic aberration (ACA) on the CSF. The CSF's of two observers were determined using red, green, blue, and white light, at 5- and 0.5-m viewing distances. At 5 m the CSF's were measured with natural vision and also with lenses which compensated the ACA. Results show that the effect of ACA on the CSF is to reduce the sensitivity to blue with respect to the red. The difference in sensitivity between these two colors is between 50 and 150% and varies with the frequency and the subject. When the ACA is compensated the influence of the color on the …

Luminance Information Is Required for the Accurate Estimation of Contrast in Rapidly Changing Visual Contexts.

2020

Summary Visual perception scales with changes in the visual stimulus, or contrast, irrespective of background illumination. However, visual perception is challenged when adaptation is not fast enough to deal with sudden declines in overall illumination, for example, when gaze follows a moving object from bright sunlight into a shaded area. Here, we show that the visual system of the fly employs a solution by propagating a corrective luminance-sensitive signal. We use in vivo 2-photon imaging and behavioral analyses to demonstrate that distinct OFF-pathway inputs encode contrast and luminance. Predictions of contrast-sensitive neuronal responses show that contrast information alone cannot ex…

Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review

2010

AbstractWe review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli - factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early …

Accommodative Functions with Multifocal Contact Lenses: A Pilot Study

2011

PURPOSE: To evaluate accommodative response and facility in presbyopic patients fitted with several types of simultaneous-image multifocal contact lenses (CLs). METHODS: Six presbyopic patients, unadapted wearers of simultaneous-image bifocals, were fitted with the Focus Progressives and the low- and high-addition Pure Vision simultaneous vision multifocal CLs. Each individual wore each of the three types of lenses in successive random order. Accommodative response, accommodative facility, visual acuity, and contrast sensitivity at distance and near were evaluated in all cases. A control group of eight non-presbyopic patients was also studied. RESULTS: The mean age was 28.6 +/- 2.72 and 51.…

Comparison of short-term light disturbance, optical and visual performance outcomes between a myopia control contact lens and a single-vision contact…

2020

Purpose To compare the optical and visual performance of a dual-focus (DF) contact lens used for myopia control with a single-vision (SV) contact lens of the same material. Methods A randomised, double-masked crossover study. Twenty-eight healthy, myopic volunteers between 18 and 32 years of age (23.49 +/- 4.07 years) participated in this study. The sensory dominant eye for distance vision was determined. Refraction, best-corrected visual acuity (VA) and aberrations for 3 mm and 5 mm pupil diameters were quantified without a contact lens in situ. Subjects were fitted with two contact lens designs: DF and SV, both made of omafilcon A material. The Quality of Vision (QoV) questionnaire, over-…

ACUITA’ VISIVA, PERFORMANCE DI LETTURA, QUALITA’ DELLA VITA E SENSIBILITA’ AL CONTRASTO SOGGETTIVA ED ELETTROFUNZIONALE IN PAZIENTI AFFETTI DA CATARA…

Prospective visual evaluation of apodized diffractive intraocular lenses

2006

To evaluate distance, intermediate, and near visual performance in patients who had multifocal apodized diffractive intraocular lens (IOL) implantation.Fernández-Vega Ophthalmological Institute, Oviedo, Spain.The best corrected distance visual acuity, best distance-corrected near visual acuity, intermediate visual acuity, distance contrast sensitivity under photopic and mesopic conditions, and patient satisfaction were measured in 325 patients and 335 patients who had bilateral implantation of the model SA60D3 IOL (AcrySof ReSTOR, Alcon) and model SN60D3 IOL (AcrySof Natural ReSTOR), respectively.At the 6-month postoperative visit, binocular best corrected distance acuity with the ReSTOR IO…

Choice of spatial frequency for contrast sensitivity evaluation after corneal refractive surgery.

2002

ABSTRACT PURPOSE: To study the utility of measurements of contrast sensitivity at different spatial frequencies as an index of visual recovery following refractive surgery. METHODS: Contrast sensitivity at 1.5, 3, 6, 12, and 18 c/deg was measured with the Stereo Optical FACT chart in 20 patients after photorefractive keratectomy (PRK) using the Nidek EC-5000 excimer laser system, and in 18 patients following laser in situ keratomileusis (LASER). Contrast sensitivity was measured preoperatively and 1, 3, 6, and 12 months after surgery. RESULTS: Results showed a statistically significant reduction (P<01) in contrast sensitivity at all spatial frequencies in PRR patients during the first an…

Luminance and contrast in visual perception of time to collision.

2013

AbstractMany animals avoid dark, approaching objects seen against a lighter background but show no or weaker reactions to stimuli with inverted contrast. We investigated whether human observers would respond differently to such stimuli in terms of estimated time-to-arrival. We varied luminances of an approaching, light or dark disk and a plain, grey background, and for several conditions, continuously adjusted calibrations so as to keep contrast and/or overall lightness constant. Since no effects were found, we conclude that humans are able to discard luminance and contrast for the task at hand. Generally, however, performance was affected by different, consecutive regimes of feedback: Init…