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Eyesight standards for beach lifeguards
Published in Mike Tipton, Adam Wooler, The Science of Beach Lifeguarding, 2018
Contrast sensitivity function (CSF) is a property of a healthy retina, which is able to enhance contrast areas in the visual field by ‘lateral inhibition’ – a within-retina process of horizontal signal coding. It is considered an important property of visual function, as objects in real life do not usually appear in full contrast, but in subtle shades of different tints. In poor lighting conditions, CSF is believed to play a more important role for visual acuity in most real-life visual tasks.
Optical and visual metrics
Published in Pablo Artal, Handbook of Visual Optics, 2017
The reciprocal of the minimum perceptible contrast is called sensitivity (Pelli and Bex 2013). The contrast sensitivity function (CSF) tells us how sensitive we are to the various frequencies of visual stimuli or, stated equivalently, tells us what is the maximum spatial frequency that we can see for each possible value of contrast. The CSF is the reciprocal of the CTF.
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
Sensitivity to variations in light intensity across the visual field, determined from the THRESHOLD contrast for a SINE WAVE GRATING. (Contrast = (Imax-Imin)/ (Ux+Imin) where Imax, I^ arc the intensities at the peak and trough of the sine wave.) The use of sine waves of different spatial frequencies gives a pure measure of the sensitivity of the VISUAL SYSTEM to contrast at various spatial scales (the contrast sensitivity function). This is greatest at a spatial frequency around 3 cycles/degree. Reduced sensitivity at lower frequencies reflects LATERAL INHIBITION in the RECEPTIVE FIELD of a retinal ganglion cell, which diminishes the neural response from gradual variations of light intensity. At high frequencies sensitivity falls to zero at the limit set by visual ACUITY.
Physical Activity Self-Efficacy in Older Adults with Vision Loss: A Grounded Theory Study
Published in Occupational Therapy In Health Care, 2023
Beth A. Barstow, Nataliya V. Ivankova, Laura K. Vogtle, Laura Dreer, Brian Geiger, Laurie A. Malone
Participants were excluded from the study if they possessed a physical condition limiting PA engagement identified using the General Health Questionnaire (GHQ). The GHQ is a non-standardized self-report consisting of a series of 17 health conditions common to older adults. Sixteen participants (10 women, 6 men) were enrolled in the study; their mean age was 81 years of age (range = 67 to 92). All participants were White except one who was Black. Six participants were from high-income neighborhoods while ten resided in middle to low income areas. Chart review revealed all participants possessed near normal to moderate deficits in visual acuity and moderate to severe impairment in contrast sensitivity function. Fifty percent had macular scotomas. Refer to Table 1 for specifics.
Clinical procedures in primary eye care, 5th edition
Published in Clinical and Experimental Optometry, 2021
The following chapter of assessment of visual function examines in detail the theory and method of measuring distance and near visual acuity across a series of visual acuity charts for adults and children. Contrast sensitivity function is described, and the procedure outlined for clinical testing. A brief genetic description of colour vision anomalies is discussed followed by procedures for routine colour vision testing in clinic for both congenital and acquired colour vision deficiencies. The chapter ends with a detailed description of visual pathways and the fundamentals of perimetry. The common perimetric testing strategies for screening and threshold measures in a clinical setting are discussed with a guide to interpretation.
Effect of vitamin D deficiency on spatial contrast sensitivity function
Published in Clinical and Experimental Optometry, 2022
In clinical practice, contrast sensitivity is commonly evaluated using sine-wave gratings in which sequential light and dark bars with unclear borders are viewed3 The number of light bars per unit length of these gratings identifies the cycle per degree (cpd) that is the unit of spatial frequency. The value of cpd is directly proportional to the level of contrast sensitivity.1 Contrast sensitivity function encompasses the changes in contrast sensitivity measured in terms of spatial frequency.