Visual acuity - Biotech, Pharma and Life Science Channel
Visual acuity (VA) is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain.
Visual acuity is a measure of the spatial resolution of the visual processing system and is usually tested in a manner to optimise and standardise the conditions. To this end, a Snellen Chart a sufficient distance away allows approximation to infinity in the way the lens attempts to focus. Twenty feet is essentially infinity from an optical perspective (the difference in optical power required to focus at 20 feet versus infinity is only 0.164 diopters). Whilst in an eye exam, lenses of varying powers are used to precisely correct for refractive errors, using a pinhole will largely correct for refractive errors and allow VA to be tested in other circumstances.
In the term "20/20 vision", the numerator refers to the distance in feet between the subject and the chart. The denominator is the distance at which the lines that make up those letters would be separated by a visual angle of 1 arc minute, which for the lowest line that is read by an eye with no refractive error (or the errors corrected) is usually 20 feet.
Source; Adapted from Wikipedia
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Videos
What is visual acuity?
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Medical and Biotech [MESH] Definitions
Neuroendoscopes
Instruments for the visual examination of interior structures related to NEUROSURGICAL PROCEDURES. There are two broad categories of neuroendoscopes, the rigid scope and the flexible scope, for various types of procedures.
Pattern Recognition, Physiological
The analysis of a critical number of sensory stimuli or facts (the pattern) by physiological processes such as vision (PATTERN RECOGNITION, VISUAL), touch, or hearing.
Whole Body Imaging
The creation of a visual display of the inside of the entire body of a human or animal for the purposes of diagnostic evaluation. This is most commonly achieved by using MAGNETIC RESONANCE IMAGING; or POSITRON EMISSION TOMOGRAPHY.
Posterior Leukoencephalopathy Syndrome
A condition that is characterized by HEADACHE; SEIZURES; and visual loss with edema in the posterior aspects of the CEREBRAL HEMISPHERES, such as the BRAIN STEM. Generally, lesions involve the white matter (nerve fibers) but occasionally the grey matter (nerve cell bodies).
Attentional Blink
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.
