The Under-compensatory Roll aVOR Does Not Affect Dynamic Visual Acuity.
Summary of "The Under-compensatory Roll aVOR Does Not Affect Dynamic Visual Acuity."
Rotations of the head evoke compensatory reflexive eye rotations in the orbit to stabilize images onto the fovea. In normal humans, the angular vestibulo-ocular reflex (aVOR) gain (eye/head velocity) changes depending on the head rotation plane. For pitch and yaw head rotations, the gain is near unity, but during roll head rotations, the aVOR gain is ∼0.7. The purpose of this study was to determine whether this physiological discrepancy affects dynamic visual acuity (DVA)-a functional measure of the aVOR that requires subjects to identify letters of varying acuities during head rotation. We used the scleral search coil technique to measure eye and head velocity during passive DVA testing in yaw, roll, and pitch head impulses in healthy controls and patients with unilateral vestibular hypofunction (UVH). For control subjects, the mean aVOR gain during roll impulses was significantly lower than the mean aVOR gain during yaw and pitch impulses; however, there was no difference in DVA between yaw, roll, or pitch. For subjects with UVH, only aVOR gain during head rotations toward the affected side (yaw) were asymmetric (ipsilesional, 0.32 ± 0.17, vs. contralesional, 0.95 ± 0.05), with no asymmetry during roll or pitch. Similarly, there was a large asymmetry for DVA only during yaw head rotations, with no asymmetry in roll or pitch. Interestingly, DVA during roll toward the affected ear was better than DVA during yaw toward the affected ear-even though the ipsilesional roll aVOR gain was 60 % lower. During roll, the axis of eye rotation remains nearly perpendicular to the fovea, resulting in minimal displacement between the fovea and fixation target image projected onto the back of the eye. For subjects with UVH, the DVA score during passive horizontal impulses is a better indicator of poor gaze stability than during passive roll or pitch.
Department of Otolaryngology Head and Neck Surgery, Johns Hopkins School of Medicine, 601 N. Caroline St, JHOC Rm 6245, Baltimore, MD, 21287-0910, USA, firstname.lastname@example.org.
This article was published in the following journal.
Name: Journal of the Association for Research in Otolaryngology : JARO
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22526736
- DOI: http://dx.doi.org/10.1007/s10162-012-0330-7
Medical and Biotech [MESH] Definitions
Corneal Wavefront Aberration
Asymmetries in the topography and refractive index of the corneal surface that affect visual acuity.
Temporary visual deficit or impaired visual processing occurring in a rapid serial visual presentation task. After a person identifies the first of two visual targets, the ability to detect the second target is impaired for the next few hundred milliseconds. This phenomenon is called attentional blink.
Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.
Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions. Visual disability refers to inability of the individual to perform specific visual tasks, such as reading, writing, orientation, or traveling unaided. (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132)
Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.
To maintain visual fixation on a distant target during head rotation, the angular vestibulo-ocular reflex (aVOR) should rotate the eyes at the same speed as the head and in exactly the opposite direct...
We investigated spatial responses of the aVOR to small and large accelerations in six canal-plugged and lateral canal nerve-sectioned monkeys. The aim was to determine whether there was spatial adapta...
Body position relative to gravity is continuously updated to prevent falls. Therefore, the brain integrates input from the otoliths, truncal graviceptors, proprioception and vision. Without visual cue...
Gain adaptation of the yaw angular vestibular ocular reflex (aVOR) induced in side-down positions has gravity-independent (global) and -dependent (localized) components. When the head oscillation angl...
ABSTRACT: BACKGROUND: When roll-tilted, the subjective visual vertical (SVV) deviates up to 40degrees from earth-vertical and trial-to-trial variability increases with head roll. Imperfections in the...
This study is evaluating reflex board training to see if it will help people who frequently roll their ankles. We are investigating several tests that evaluate the ability of the neuromus...
The purpose of this study is to see if dynamic contrast enhanced (DCE) MRI imaging makes it possible to distinguish benign conditions of the breast from malignant tumors and provide better...
Reading can be an uncomfortable and difficult task for some people. Symptoms include unpleasant somatic and perceptual effects, such as eye-strain, headache, and blurred text, despite norm...
This study will use a method called dynamic light scattering (DLS) to study the lens of the eye in young normal subjects. The DLS device uses a very dim laser light to study the lens of th...
The purpose of this study is to evaluate whether this new method of taking pictures called Dynamic Area Telethermometry (DAT) might be a good way of looking at patients with cancer that is...