Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ADAPTATION, OCULAR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources
PubMed1987

Simultaneous opposing adaptive changes in cat vestibulo-ocular reflex direction for two body orientations.

The specificity of adaptation of vestibulo-ocular reflex direction was examined by exposing cats to combined pitch vestibular rotation and horizontal optokinetic motion at 0.25 Hz, while alternating body position between lying on the left side and lying on the right. The direction of optokinetic motion relative to head motion was reversed when the cat's body posture was changed so that, for example, if head upward rotation was coupled to leftward visual world motion when the cat was lying on its left side, then head upward rotation was coupled to rightward visual world motion when the cat was on its right side. Body position and optokinetic motion direction were changed every 10 min for a total of 2 h of adaptation on each side. Horizontal and vertical electrooculographic recordings were made during pitch rotations in darkness before and after adaptation. Saccades were removed from the records and vestibulo-ocular reflex gain was measured in the direction of optokinetic motion. In every case, the adaptation procedure produced a directional change in the vestibulo-ocular reflex specific to the posture during measurement and appropriate to reduce the retinal image motion caused by the combined vestibular and optokinetic stimuli. That is, adaptive horizontal eye movements measured on the two sides were in opposite directions for the same direction of head motion. This specificity suggests that adaptation of vestibulo-ocular reflex direction involves specific neural pathways that are controlled by body orientation signals which most likely arise from the otolith organs.

Adaptation, Physiological↗
PubMed1990

Adaptation to optically-increased interocular separation under naturalistic viewing conditions.

Mirror spectacles which enhance binocular disparity by optically doubling the normal separation between the eyes were used to create conditions of combined perceptual and oculomotor conflict. Apparent depth and distance, as well as tonic accommodation, tonic vergence, and accommodative-vergence gain (response AC/A ratio), were assessed immediately before and after a 30 min exposure period of naturalistic viewing with the spectacles. Wearing the spectacles produced an increase in tonic vergence, and perceptual aftereffects consisting of increased apparent distance and depth. The results indicate that oculomotor conflict associated with enhanced interocular separation may be resolved through adaptation of tonic vergence, rather than through alteration of accommodative-vergence gain. The results also demonstrate that perceptual conflict between disparity and multiple veridical depth cues does not necessarily produce adaptive modification of the relationship between binocular disparity and apparent depth.

Accommodation, Ocular↗
PubMed1985

Nearpoint visual stress: clinical implications.

A physiological model of nearpoint stress, based on autonomic arousal, was presented in a companion paper. This paper deals with clinical implications of the nearpoint stress model, including clinical manifestations, adaptive responses to nearpoint stress, and management of nearpoint stress-induced vision disorders.

Accommodation, Ocular↗
PubMed1984

Adaptation of tonic accommodation.

We compared the resting (dark) focus of accommodation before and after adapting to accommodative stimuli placed nearer or farther from an initial baseline resting focus. Short-term monocular adaptation (less than 2 min) did not result in consistent after-effects that were correlated with the adaptation stimulus. After short-term adaptation, accommodation returned to its resting level in 2-15 s. Long-term monocular adaptation (30 min) to a 6-D near stimulus resulted in a small (0.5-D) average increase in the resting focus of accommodation beyond the normal 2-15-s short-term decay. These observations illustrate a tonic adaptation of accommodation that is small and requires longer durations of adaptation than an analogous adaptation of the fusional vergence system to prism.

Accommodation, Ocular↗
PubMed1964

QUANTITATIVE STUDIES ON PIGMENT MIGRATION AND LIGHT SENSITIVITY IN THE COMPOUND EYE AT DIFFERENT LIGHT INTENSITIES.

Comparative electrophysiological and histological studies were made on the functional significance of the secondary iris pigment migration for the sensitivity of the eye in the noctuid moth Cerapteryx graminis. The pigment position at different adapting light intensities was studied as well as the influence of different positions on the sensitivity of the eye. Adapting light intensities above a certain value hold the pigment in light position. At a 3 log units lower intensity the pigment is brought into dark position and at light intensities between these limiting values the pigment attains intermediate positions. The results indicate that at light intensities between the limiting values the pigment shifts closely follow the changes in intensity of the environmental light. With the pigment in dark position the eye is about 1000 times more sensitive than when the pigment is in light position, there being a close relationship between the sensitivity of the eye and the position of the pigment at intermediate positions.

Adaptation, Ocular↗
PubMed1983

Adaptive change of the vestibulo-ocular reflex in the cat: the effects of a long-term frequency-selective procedure.

Ocular movements of naive and adapted cats were recorded by classical electronystagmography techniques during: (1) sinusoidal vestibular stimulation, (2) sinusoidal optokinetic stimulation, (3) sinusoidal additive visual-vestibular stimulation, and (4) sinusoidal conflicting visual-vestibular stimulation. Adaptation of the horizontal vestibulo-ocular reflex (VOR) was produced in adult cats by sustained combined sinusoidal rotation of the cat and its surroundings (fixed-field conditions). This procedure was applied for four hours for four consecutive days. On the fifth day the VOR in darkness, the OKR, the VOR in the light and the visual suppression of the VOR were studied. VOR gain decreased from day to day and some relative frequency-specificity emerged. The gain of the visually inhibited VOR also diminished after training. This change was also frequency-specific. OKN gain, tested by a set of sinusoidal rotations, was found to be virtually unchanged. In the naive cat, VOR modified by the visual stimulus (fixed or moving) could be computed by an algebraic summation of the VOR and OKR eye movement compensations. After training, the gain of the VOR in situations where the VOR was interacting with the OKR remained easily predictable by the algebraic summation of the isolated VOR and OKR compensations.

Animals↗
PubMed1986

Dynamic interactions between accommodation and convergence are velocity sensitive.

Aftereffects of accommodation and vergence occur following approximately 1 min of adaptation to lenses and prisms respectively. This observation can be interpreted to mean that accommodation and vergence responses have phasic and tonic components. We have examined the role that these proposed subcomponents play in mutual interactions between accommodation and vergence. Both accommodative vergence (AV) and vergence accommodation (VA) were unresponsive to low temporal frequency variations (less than 0.1 Hz) in defocus and disparity respectively. However, both AV and VA were responsive to higher temporal frequency stimuli (up to 0.5 Hz). When negative feedback to the stimulated system was cancelled electronically, both AV and VA become responsive to low temporal frequency stimuli. The ratio or gain of accommodative vergence/accommodation (AC/A) and vergence accommodation/vergence (CA/C) increased nonlinearly with stimulus amplitude. Vergence aftereffects resulted from stimulation of AV and accommodative aftereffects resulted from stimulation of VA. These results are interpreted to mean there could be a complementary relationship between the amplitude of the AC/A ratio and proposed tonic adaptation of accommodation, and between the amplitude of the CA/C ratio and proposed tonic adaptation of vergence. A low saturation limit or stimulus window for tonic adaptation may account for the amplitude dependent nonlinearities of the AC/A and CA/C ratios.

Accommodation, Ocular↗
PubMed2002

The history of research into the disorders of reading and accommodation in strabismic amblyopia.

During the past 150 years, research on amblyopia and nystagmus has developed in five different waves (W1-W5). Amblyopia was initially regarded to be enigmatic and believed to be related to eccentric fixation (W1, after 1850); later, it was ascribed to disorders in refraction or accommodation (W2, around 1900). After 1900 (W3), phylogenetic explanations appeared, and after 1945 (W4) concepts based on successful orthoptic practice came to the fore. Since 1965 (W5), research on amblyopia has been guided by modern insights into neuroanatomy and neurophysiology. In contrast to amblyopia, nystagmus has always been a well-defined symptomatic entity. Even though amblyopia and nystagmus are both symptoms of strabismus, their understanding has therefore developed along different paths. In juvenile strabismus, defects in binocularity lead to monolateral amblyopia, while defects in contour vision lead to bilateral nystagmus. In the present paper, these five waves of amblyopia research are described in more detail, with particular attention to the concepts of adaptation, visual fields, and sensory and motor functions as related to disorders in reading and accommodation.

Accommodation, Ocular↗