The Effects of Changing Light Levels on Contrast Sensitivity in Patients With Glaucoma

AbstractThe validity of the Barten theoretical model for describing the vertebrate spatial contrast sensitivity function (CSF) and acuity at scotopic light levels has been examined. Although this model (which has its basis in signal modulation transfer theory) can successfully describe vertebrate CSF, and its relation to underlying visual neurophysiology at photopic light levels, significant discrepancies between theory and experimental data have been found at scotopic levels. It is shown that in order to describe scotopic CSF, the theory must be modified to account for important mechanistic changes, which occur as cone vision switches to rod vision. These changes are divided into photon management factors [changes in optical performance (for a dilated pupil), quantum efficiency, receptor sampling] and neural factors (changes in spatial integration area, neural noise, and lateral inhibition in the retina). Predictions of both scotopic CSF and acuity obtained from the modified theory were found to be in good agreement with experimental values obtained from the human, macaque, cat, and owl monkey. The last two species have rod densities particularly suited for scotopic conditions.

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Luminance and chromatic contrast sensitivity at high light levels

Journal of Vision ◽

10.1167/19.10.70b ◽

2019 ◽

Vol 19 (10) ◽

pp. 70b ◽

Cited By ~ 1

Author(s):

Sophie Wuerger ◽

Rafal Mantiuk ◽

Maria Perez-Ortiz ◽

Jasna Martinovic

Keyword(s):

Contrast Sensitivity ◽

High Light ◽

Chromatic Contrast ◽

Light Levels ◽

Chromatic Contrast Sensitivity

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Interspecific variation in the response of growth, crown morphology, and survivorship to light of six tree species in the conifer belt of the Bhutan Himalayas

Canadian Journal of Forest Research ◽

10.1139/x03-281 ◽

2004 ◽

Vol 34 (5) ◽

pp. 1093-1107 ◽

Cited By ~ 28

Author(s):

Georg Gratzer ◽

Andras Darabant ◽

Purna B Chhetri ◽

Prem Bahadur Rai ◽

Otto Eckmüllner

Keyword(s):

Tree Species ◽

Radial Growth ◽

Interspecific Variation ◽

Low Light ◽

Continuous Growth ◽

Light Levels ◽

Shade Tolerant Species ◽

Lower Light ◽

Crown Morphology ◽

Changing Light

The responses of radial and height growth, plant architecture, and the probability of mortality of saplings to varying light levels were quantified for six tree species in temperate conifer forests of the Bhutan Himalayas. Increases in growth with increasing light were comparable with those of high latitude tree species but lower than those of tropical tree species and temperate species in North America. The shade-tolerant species Tsuga dumosa (D. Don.) Eichler showed the strongest increase in radial growth at low light and reached asymptotic growth early. It had the deepest crowns in low light and a low decrease of leader growth with decreasing light. It represents a continuous growth type, which invests in height rather than lateral growth under low light conditions. Betula utilis D. Don. showed greater increases in radial growth and a higher mortality at low light than the more shade-tolerant Abies densa Griff., in keeping with the trade-off between survivorship and growth at low light. Picea spinulosa Griff, Larix griffithiana Carriére, and Pinus wallichiana A.B. Jackson showed small increases in growth at low light levels. The latter two species showed no capacity to adapt their morphology in response to changing light levels, which resulted in higher probabilities of mortality at lower light levels. Differences in the probability of mortality at different light levels were more pronounced than differences in the light-growth response, underlining the importance of survivorship at low light for successional dynamics.

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Two explanations of the dawn chorus compared: how monotonically changing light levels favour a short break from singing

Animal Behaviour ◽

10.1006/anbe.2002.3091 ◽

2002 ◽

Vol 64 (4) ◽

pp. 527-539 ◽

Cited By ~ 37

Author(s):

John M.C. Hutchinson

Keyword(s):

Dawn Chorus ◽

Light Levels ◽

Changing Light

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Light-regulated collective contractility in a multicellular choanoflagellate

10.1101/661009 ◽

2019 ◽

Cited By ~ 2

Author(s):

Thibaut Brunet ◽

Ben T. Larson ◽

Tess A. Linden ◽

Mark J. A. Vermeij ◽

Kent McDonald ◽

...

Keyword(s):

Animal Movement ◽

Swimming Behavior ◽

Undescribed Species ◽

Caribbean Island ◽

Sensory Inputs ◽

Light Levels ◽

Cgmp Pathway ◽

The Caribbean ◽

Tissue Deformations ◽

Changing Light

AbstractCollective cell contractions that generate global tissue deformations are a signature feature of animal movement and morphogenesis. Nonetheless, the ancestry of collective contractility in animals remains mysterious. While surveying the Caribbean island of Curaçao for choanoflagellates, the closest living relatives of animals, we isolated a previously undescribed species (here namedChoanoeca flexasp. nov.), that forms multicellular cup-shaped colonies. The colonies rapidly invert their curvature in response to changing light levels, which they detect through a rhodopsin-cGMP pathway. Inversion requires actomyosin-mediated apical contractility and allows alternation between feeding and swimming behavior.C. flexathus rapidly converts sensory inputs directly into multicellular contractions. In this respect, it may inform reconstructions of hypothesized animal ancestors that existed before the evolution of specialized sensory and contractile cells.One Sentence SummaryA newly described choanoflagellate species forms cup-shaped colonies that reversibly invert their curvature in response to light.

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