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Results for “ADAPTATION, OCULAR”

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At least 1,495 records · Page 83Linked to original sources
PubMed1998

Dynamic characteristics and adaptability of mouse vestibulo-ocular and optokinetic response eye movements and the role of the flocculo-olivary system revealed by chemical lesions.

The dynamic characteristics of reflex eye movements were measured in two strains of chronically prepared mice by using an infrared television camera system. The horizontal vestibulo-ocular reflex (HVOR) and horizontal optokinetic response (HOKR) were induced by sinusoidal oscillations of a turntable, in darkness, by 10 degrees (peak to peak) at 0.11-0.50 Hz and of a checked-pattern screen, in light, by 5-20 degreesat 0.11-0.17 Hz, respectively. The gains and phases of the HVOR and HOKR of the C57BL/6 mice were nearly equivalent to those of rabbits and rats, whereas the 129/Sv mice exhibited very low gains in the HVOR and moderate phase lags in the HOKR, suggesting an inherent sensory-motor anomaly. Adaptability of the HOKR was examined in C57BL/6 mice by sustained screen oscillation. When the screen was oscillated by 10 degrees at 0.17 Hz, which induced sufficient retinal slips, the gain of the HOKR increased by 0.08 in 1 h on average, whereas the stimuli that induced relatively small or no retinal slips affected the gain very little. Lesions of the flocculi induced by local applications of 0. 1% ibotenic acid and lesions of the inferior olivary nuclei induced by i.p. injection of 3-acetylpyridine in C57BL/6 mice little affected the dynamic characteristics of the HVOR and HOKR, but abolished the adaptation of the HOKR. These results indicate that the olivo-floccular system plays an essential role in the adaptive control of the ocular reflex in mice, as suggested in other animal species. The data presented provide the basis for analyzing the reflex eye movements of genetically engineered mice.

Animals↗
PubMed1987

Vestibulo-ocular reflex during magnified vision: adaptation to reduce visual-vestibular conflict.

This report describes the short-term effect of 2.2X telescopic spectacles on the vestibulo-ocular reflex (VOR) in seven volunteers. VOR gain was initially measured in darkness and light during passive sinusoidal rotations. Subjects were then rotated in light for 15 min while wearing telescopic spectacles. Dynamic visual acuity (DVA), vision during head rotation, was measured with telescopic spectacles. Initial VOR gain in darkness was 0.74 +/- 0.10 (mean +/- S.D.); VOR gain with unmagnified vision was 1.07 +/- 0.04. Initial VOR gain with magnified vision was 1.37 +/- 0.53. DVA was poorer than static acuity in three of four subjects. After adaptation, VOR gain in darkness increased to 0.83 +/- 0.12, with six of seven subjects exhibiting a gain increase of 7-23% (p less than 0.05 for 5). Adapted VOR gain with magnified vision was 1.54 +/- 0.25. Adapted performance was more consistent and oscillopsia was reduced. Adapted DVA improved 30-100% in four subjects. These changes indicate VOR adaptation to telescopic spectacles decreases visual-vestibular conflict.

Adaptation, Physiological↗
PubMed2006

Time course and development of light adaptation processes in the outer zebrafish retina.

Retinomotor movements are morphological changes in the outer retina in response to changing light conditions. They can be separated into two components: Migration of pigment granules within the microvilli of the retinal pigment epithelium (RPE) and positional changes in photoreceptor cells. These positional changes optimize exposure of the cone and rod photoreceptors to light. The aim of this study was to analyze both the time course of retinomotor movements in the adult zebrafish and the maturation of these processes in the developing fish. We show that retinomotor movements are used as a dark/light adaptation mechanism in zebrafish. In adult zebrafish, melanin granules of the RPE migrate with constant speed and reach the fully light adapted (LA) state approximately after 1 h. In contrast, about two thirds of double cone outer segment movements are finished in 5 min, and are fully completed in 10 to 20 min. During development there are three crucial stages leading to mature retinomotor movements in response to light: at 5 dpf (days post fertilization) the migration of pigment granules begins, at 20 dpf the pigment granules condense in the apical part of the RPE microvilli, and at 28 dpf, concomitant with the functional maturation of rods, the double cones contract as in adult retinas.

Adaptation, Ocular↗
PubMed2003

Lazy eyes zebrafish mutation affects Müller glial cells, compromising photoreceptor function and causing partial blindness.

A behavioral assay based on the optokinetic reflex was used to screen chemically mutagenized zebrafish larvae for deficits in visual function. A homozygous recessive mutation, lazy eyes (lze), was isolated based on the observation that 5-day postfertilization (dpf) mutants displayed weaker and less frequent eye movements than wild-type fish in response to moving stripes. Electroretinographic (ERG) recordings revealed that mutants had severely reduced a- and b-wave amplitudes relative to wild-type fish, indicating outer retinal dysfunction. Retinal lamination and cellular differentiation were normal in the lze retina; however, mutant photoreceptor cells had small outer segments and pyknotic nuclei were occasionally observed in the outer retina and the marginal zone of lze. Cone, rod, amacrine, bipolar, and Müller cell marker analyses indicated that the typical lze retina contained fewer rod photoreceptors and fewer Müller cells than wild-type fish at 5 dpf. At 3 dpf, however, mutant retinas had normal numbers of rod photoreceptors and Müller cells, suggesting that the initial differentiation of these cell types occurred normally. Rod photoreceptor histology was normal at this early stage, but Müller cells were often hypertrophied, suggesting that they were unhealthy. Constant light rearing of mutant animals accelerated the Müller cell degeneration, severely worsened the visual deficit, but had no obvious affect on the photoreceptors. When ERG responses and Müller cell degeneration from the same mutant animals were analyzed, the extent of the Müller cell loss matched closely the degree to which ERG responses were reduced. In summary, the lze gene appears to be required for Müller cell viability and normal visual function. The lze mutant may be a model for the study of the involvement of Müller cells in photoreceptor development and function.

Adaptation, Ocular↗
PubMed2001

Structure and functional connections of presynaptic terminals in the vertebrate retina revealed by activity-dependent dyes and confocal microscopy.

The fluorescent dyes sulforhodamine 101 (SR 101) and FM1-43 were used as activity-dependent dyes (ADDs) to label presynaptic terminals in the retinas of a broad range of animals, including amphibians, mammals, fish, and turtles. The pattern of dye uptake was studied in live retinal preparations by using brightfield, fluorescence, and confocal microscopy. When bath-applied to the retina-eyecup, these dyes were avidly sequestered by the presynaptic terminals of virtually all rods, cones, and bipolar and amacrine cells; ganglion cell dendrites and horizontal cells lacked significant dye accumulation. Other structures stained with these dyes included pigment epithelial cells, cone outer segments, and Müller cell end-feet. Studies of dye uptake in dark- and light-adapted preparations showed significant differences in the dye accumulation pattern in the inner plexiform layer (IPL), suggesting a dynamic, light-modulated control of endocytotic activity. Presynaptic terminals in the IPL could be segregated on the basis of volume: bipolar varicosities in the IPL were typically larger than those of amacrine cells. The combination of retrograde labeling of ganglion cells and presynaptic terminal labeling with ADDs served as the experimental preparation for three-dimensional reconstruction of both structures, based on dual detector, confocal microscopy. Our results demonstrate a new approach for studying synaptic interactions in retinal function. These findings provide new insights into the likely number and position of functional connections from amacrine and bipolar cell terminals onto ganglion cell dendrites.

Adaptation, Ocular↗
PubMed1992

Color electroretinography. A method for separation of dysfunctions of cones.

Electroretinograms to white and color stimuli were recorded in four normal subjects and nine subjects with different cone dysfunctions, including protanopia, cone dystrophy, cone dystrophy with supernormal b-waves at dark adaptation, cone dystrophy with missing b-waves during light adaptation and rod-cone dystrophy with blue cone hypersensitivity. Color stimuli were obtained with Kodak Wratten filters in blue, blue-green, green, yellow and red. Electroretinograms to all stimuli were recorded during dark and light adaptation with different stimulus intensities and to 30-Hz flicker stimulation. In protanopia, responses to red during light adaptation and flicker stimulation were reduced. All cone dystrophies showed reduced amplitudes and prolonged implicit times to red when dark adapted. The light-adapted responses were equally reduced to all color stimuli in cone dystrophy and cone dystrophy with supernormal b-waves. Contrary to other cone dystrophies, in cone dystrophy with missing b-waves, responses to red were severely reduced and responses to green were preserved, indicating a predominantly red cone dysfunction. Blue cone hypersensitivity was clearly distinct from other dystrophies in having large response to blue and blue-green and much smaller responses to all other colors in all stimulus conditions. The electroretinogram with color stimuli allowed separation of different cone dysfunctions and identification of new retinal dysfunction syndromes.

Adaptation, Ocular↗
PubMed1977

Involutional diabetic retinopathy.

The end-stage or involutional phase of proliferative diabetic retinopathy may result in stabilization of vision for long periods of time. However, the clinical resemblance to the progressive tapetoretinal degenerations suggests that marked functional impairment of the retina is present in such eyes. We studied 19 eyes with involutional retinopathy to document the status of the retinal function. Studies included fluorescein angiography, visual field examination, dark adaptation testing, color vision testing, electro-oculography and electroretinography (ERG). The results indicated marked functional abnormalities in all eyes. The ERG tracings showed uniformly subnormal responses and delayed implicit times, similar to those of dominantly inherited retinal pigment degeneration, and indicative of a progressive retinal disorder. In two patients, color vision testing showed defects similar to those seen in inherited tritanopia; and in the remaining patients, defects were indicative of an acquired blue-yellow dyschomatopsia.

Adaptation, Ocular↗
PubMed1981

Alteration of GABA system in frog retina following short light and dark adaptations - a quantitative comparison with retinal taurine.

Effect of short light and dark adaptations on retinal GABA and taurine was studied using bull frog (Rana catesbiana). The retinal GABA was increased significantly in light-adapted state, and this increase was accompanied by the increases of L-glutamate decarboxylase (GAD) activity and [3H]-GABA release. The activation of retinal GABA-transaminase succinic semialdehyde dehydrogenase (GABA-T:SSADH) was also observed after a lag period of several hours. Under the same experimental conditions, however, no significant changes were noted in retinal taurine content and cysteine sulfinate decarboxylase (CSD) activity. These findings suggest that a short light adaptation induces differential effects on retinal GABA and taurine, and the activation of GABAergic neurons in the retina may be involved in the process of short light adaptation.

Adaptation, Ocular↗
PubMed1984

Color fundamentals deduced from carp ganglion cell responses.

Retinal ganglion cell responses were used to derive the action spectra (fundamentals) of the photopic color mechanisms in carp. Both silencing and chromatic adaptation techniques were used. The former proved to be more successful than the latter, because weak (even subthreshold) dynamic signals in one mechanism (mostly the red) caused strong effects on the other mechanisms. With chromatic adaptation these interacting signals were unavoidable, whereas with the silencing technique the modulation of the silenced mechanism was eliminated. The resultant pure action spectra agree well with the electrophysiological data of cone pedicles and horizontal cells. They differ, however, from the log-absorption specta found by microspectrophotometry. Apart from the differences in the slope of the long wavelength tails, the spectra also differ in the short wavelength region. The latter may indicate that in A-2 pigments, the beta-band absorption has a lower efficiency than the main-band absorption.

Action Potentials↗