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Progress in Brain Research 2001
Review
Topics: Animals; Calcium; Dark Adaptation; Electroretinography; Models, Neurological; Photoreceptor Cells; Retina; Retinal Pigments; Sensory Thresholds; Vision, Ocular
PubMed: 11420957
DOI: 10.1016/s0079-6123(01)31031-2 -
Journal of Experimental Zoology. Part... Nov 2020
Topics: Adaptation, Biological; Animals; Behavior, Animal; Biological Evolution; Caves; Characidae; Dark Adaptation; Darkness
PubMed: 33258551
DOI: 10.1002/jez.b.23014 -
The British Journal of Ophthalmology Jun 1994
Topics: Dark Adaptation; Humans; Kinetics; Macular Degeneration; Retinal Diseases; Retinitis Pigmentosa
PubMed: 8060922
DOI: 10.1136/bjo.78.6.426 -
Eye (London, England) 1998Following exposure of the eye to an intense light that 'bleaches' a significant fraction of the rhodopsin, one's visual threshold is initially greatly elevated, and... (Review)
Review
Following exposure of the eye to an intense light that 'bleaches' a significant fraction of the rhodopsin, one's visual threshold is initially greatly elevated, and takes tens of minutes to recover to normal. The elevation of visual threshold arises from events occurring within the rod photoreceptors, and the underlying molecular basis of these events and of the rod's recovery is now becoming clearer. Results obtained by exposing isolated toad rods to hydroxylamine solution indicate that, following small bleaches, the primary intermediate causing elevation of visual threshold is metarhodopsin II, in its phosphorylated and arrestin-bound form. This product activates transduction with an efficacy about 100 times greater than that of opsin.
Topics: Animals; Bufo marinus; Dark Adaptation; Humans; Hydroxylamine; Retinal Rod Photoreceptor Cells; Rhodopsin
PubMed: 9775211
DOI: 10.1038/eye.1998.139 -
Acta Medica Orientalia 1952
Topics: Adaptation, Ocular; Dark Adaptation; Eye; Pregnancy; Vision, Ocular
PubMed: 12975994
DOI: No ID Found -
Investigative Ophthalmology & Visual... Mar 2009To investigate dark adaptation during hypoxia in patients with chronic respiratory failure.
PURPOSE
To investigate dark adaptation during hypoxia in patients with chronic respiratory failure.
METHODS
At three visits, dark adaptation was recorded by computerized dark adaptometry in 13 patients with chronic respiratory insufficiency treated by long-term oxygen therapy. At visits 1 and 3, the patients were administered their usual oxygen supplement. At visit 2, no oxygen was given. At each visit, an analysis of arterial blood gases measured pH, partial pressure of O(2) (Pao(2)), partial pressure of CO(2) (Paco(2)), base excess (BE), standard bicarbonate (HCO(3)), and arterial oxygen saturation. Pulse oximetry (POX) was also recorded.
RESULTS
Significant differences were recorded between visits 1 and 2 and between visits 2 and 3 for Pao(2), arterial oxygen saturation, and POX; no differences were found for pH, Paco(2), BE, or HCO(3). No differences were seen between visits 1 and 3 for any of the laboratory parameters. All patients had normal and unchanged dark adaptation at the three visits.
CONCLUSIONS
Hypoxia in chronic respiratory insufficiency was associated with normal dark adaptation, in contrast to hypoxia in healthy persons at high altitudes, which is known to produce impaired dark adaptation. The result may partly reflect the influence of Paco(2) on the lumen of choroidal and retinal vessels. At high altitudes, with hypocapnic vasoconstriction the oxygen supply to the retina is further compromised, resulting in reduced dark adaptation. The authors hypothesize that respiratory insufficiency with hypercapnia or normocapnia will have larger choroidal and retinal vessel lumens, added to by further dilation of retinal vessels during hypoxia. The tentative net effect would be preserved dark adaptation.
Topics: Aged; Aged, 80 and over; Blood Gas Analysis; Chronic Disease; Dark Adaptation; Female; Humans; Hydrogen-Ion Concentration; Hypoxia; Male; Middle Aged; Oximetry; Oxygen; Partial Pressure; Respiratory Insufficiency
PubMed: 18936146
DOI: 10.1167/iovs.08-2104 -
Scandinavian Journal of Psychology 1992It has previously been suggested that long-term dark adaptation is controlled by bleaching signals that regulate the activity of an allosteric, positively cooperative... (Review)
Review
It has previously been suggested that long-term dark adaptation is controlled by bleaching signals that regulate the activity of an allosteric, positively cooperative protein (Stabell et al., 1986a, b). Recent biochemical evidence strongly supports this assumption, indicating that the primary regulator of the light-sensitive channels in the plasma membrane of the outer segments of the photoreceptors is a homo-oligomeric, allosteric, positively cooperative protein. In this report, we discuss the possibility that signals from bleached photopigments may control the dark-adaptation process through the allosteric protein of the plasma membrane. It is suggested that the concentrations of the bleached photopigment and of the allosteric effector are reciprocal quantities.
Topics: Animals; Dark Adaptation; Humans; Models, Neurological; Photoreceptor Cells; Retinal Pigments
PubMed: 1594893
DOI: 10.1111/j.1467-9450.1992.tb00808.x -
Vision Research Nov 1999Older adults have serious difficulty seeing under low illumination and at night, even in the absence of ocular disease. Optical changes in the aged eye, such as...
Older adults have serious difficulty seeing under low illumination and at night, even in the absence of ocular disease. Optical changes in the aged eye, such as pupillary miosis and increased lens density, cannot account for the severity of this problem, and little is known about its neural basis. Dark adaptation functions were measured on 94 adults ranging in age from the 20s to the 80s to assess the rate of rod-mediated sensitivity recovery after exposure to a 98% bleach. Fundus photography and a grading scale were used to characterize macular health in subjects over age 49 in order to control for macular disease. Thresholds for each subject were corrected for lens density based on individual estimates, and pupil diameter was controlled. Results indicated that during human aging there is a dramatic slowing in rod-mediated dark adaptation that can be attributed to delayed rhodopsin regeneration. During the second component of the rod-mediated phase of dark adaptation, the rate of sensitivity recovery decreased 0.02 log unit/min per decade, and the time constant of rhodopsin regeneration increased 8.4 s/decade. The amount of time to reach within 0.3 log units of baseline scotopic sensitivity increased 2.76 min/decade. These aging-related changes in rod-mediated dark adaptation may contribute to night vision problems commonly experienced by the elderly.
Topics: Adult; Aged; Aged, 80 and over; Aging; Dark Adaptation; Humans; Middle Aged; Retinal Rod Photoreceptor Cells
PubMed: 10748929
DOI: 10.1016/s0042-6989(99)00092-9 -
Federation Proceedings 1946
Topics: Accommodation, Ocular; Dark Adaptation; Eye; Humans; Vision Tests
PubMed: 21020738
DOI: No ID Found -
Gerontology 1991The human eye is capable of adjusting to wide variations in light intensity by altering the pupil size and the sensitivity of the retina to light. Falls are one of the...
The human eye is capable of adjusting to wide variations in light intensity by altering the pupil size and the sensitivity of the retina to light. Falls are one of the commonest problems of old age, and the causes are multifactorial. As falls often occur at night, this study was designed to compare dark adaptation in groups of elderly fallers and non-fallers. Twenty-two female patients in a geriatric assessment ward were included in the study and classified as 'fallers' or 'non-fallers'. A full ophthalmic examination was performed on each subject, and dark adaptation measured, in a single-blind fashion, using the Friedmann visual field analyser; following initial bleaching of the retinal photoreceptors, the room was placed in total darkness and retinal sensitivity measured every minute for 20 min. The values, expressed as log filter density, were plotted against duration of time in the dark. The mean values at 5 min were 0.9 in the fallers and 1.4 in the non-fallers (p less than 0.02 unpaired t test) and at 20 min 2.2 and 3.2, respectively (p less than 0.04). These results indicate reduced retinal sensitivity and hence impaired dark adaptation in the falling group. Lighting levels in the homes of many old people have been shown to be inadequate. Impaired dark adaptation may leave an elder person virtually blind for a minute or more on moving from a bright room to a darker area. The provision of night lights in the homes of recurrent fallers may offset the influence of impaired dark adaptation.
Topics: Accidental Falls; Aged; Aged, 80 and over; Dark Adaptation; Female; Humans; Lighting
PubMed: 1916313
DOI: 10.1159/000213264