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Results for “ACCOMMODATION, OCULAR”

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At least 37 records · Page 2Linked to original sources
PubMed1985

Ultrasound measures of vitreous chamber depth during ocular accommodation.

The vitreous chamber decreased in depth about 0.12 mm as accommodative demand increased from 0.2 to 7 D in nine accommodative steps. The depth decreases matched movement of the posterior lens surface toward the retina. Accommodation caused no significant increases in axial length compared to cyclopleged controls. These results do not favor the active role for the vitreous in accommodation proposed by Coleman in 1970. Computer analysis of A-scan interval counts demonstrated that multiple retinal complex peaks might erroneously point to vitreous or axial lengthening. About 30% of total lens thickening during accommodation was accounted for by posterior lens surface displacement.

Accommodation, Ocular↗
PubMed1995

Spectral bandwidth and ocular accommodation.

Previous studies have suggested that targets illuminated by monochromatic (narrow-band) light are less effective in stimulating the eye to change its focus than are black-white (broadband) targets. The present study investigates the influence of target spectral bandwidth on the dynamic accommodation response in eight subjects. The fixation target was a 3.5-cycle/deg square-wave grating illuminated by midspectral light of various bandwidths [10, 40, and 80 nm and white (CIE Illuminant B)]. The target was moved sinusoidally toward and away from the eye, and accommodation responses were recorded and Fourier analyzed. Accommodative gain increases, and phase lag decreases, with increasing spectral bandwidth. Thus the eye focuses more accurately on targets of wider spectral bandwidth. The visual system appears to have the ability to analyze polychromatic blur to determine the state of focus of the eye for the purpose of guiding the accommodation response.

Accommodation, Ocular↗
PubMed2001

Using diplopia as a warning of an inappropriate visual (ocular) accommodative response (WIVAR).

BACKGROUND: Over-accommodation, a tendency to focus at a distance closer than the desired distance, has been previously shown to occur when using a head-up display (HUD). METHODS: A simple system was developed as a warning of an inappropriate visual accommodative response (WIVAR) during flight training. Two lines, which are seen as four low-contrast lines (physiological diplopia) if the user is focused in the distance due to the link between convergence and accommodation, are projected onto the pilot's HUD combiner. RESULTS: The results show that by using the WIVAR system the accommodative response can be kept more distant when viewing forward-looking infra-red imagery (by 0.12 +/- 0.04 D; p < 0.05), performing a high cognitive workload task (by 0.07 +/- 0.03 D; p < 0.05) and especially when viewing in a Ganzfeld (by 0.41 +/- 0.12 D; p < 0.01). CONCLUSION: While collimated HUD imagery stimulates the user to a more distant focus, the use of the WIVAR lines can cause additional relaxation of accommodation.

Accommodation, Ocular↗
PubMedDate not supplied

[Effect of noise on ocular accommodation].

The goal of investigations was the determination of connection between the level of noise and the extra-auditory reaction of the organism--a change of the near point. Changes of accommodation determined by means of a black-and-white check-board test were monitored in the course and after 1 hour exposition to noise of 90 dB-A, 93 dB-A, 96 dB-A or 99 dB-A of the sound level. The results show that the deterioration of vision is a complicated exponential function of the intensity and time of the exposition to noise.

Accommodation, Ocular↗
PubMed1973

Vestibular influences on ocular accommodation in cats.

Electrical stimulation of the utricle in C-1 transected cats (whose labyrinths remained sensitive to natural stimulation) induced bilateral pupillary dilatation and bilateral 0.4 to 3.0 diopter lens change in an anti-accommodative direction. Both effects could still be induced two weeks after cutting the ipsilateral cervical sympathetic trunk. It is concluded that these effects take place by inhibiting the parasympathetic pathway originating in the Edinger-Westphal nucleus. The mediating pathways from the vestibular complex to the Edinger-Westphal nucleus pass through the brain stem in the region outside the medial longitudinal fasciculi.

Accommodation, Ocular↗