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The definition of 6/6 is somewhat arbitrary, since human eyes typically have higher acuity, as Tscherning writes, "We have found also that the best eyes have a visual acuity which approaches 2, and we can be almost certain that if, with a good illumination, the acuity is only equal to 1, the eye presents defects sufficiently pronounced to be ...
Visual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight , sight or vision . The various physiological components involved in vision are referred to collectively as the visual system , and are the focus of much research in psychology ...
This is different from visual acuity, which refers to how clearly a person sees (for example "20/20 vision"). A person can have problems with visual perceptual processing even if they have 20/20 vision. The resulting perception is also known as vision, sight, or eyesight (adjectives visual, optical, and ocular, respectively).
Visual acuity, or resolving power, is "the ability to distinguish fine detail" and is the property of cone cells. [42] It is often measured in cycles per degree (CPD), which measures an angular resolution, or how much an eye can differentiate one object from another in terms of visual angles. Resolution in CPD can be measured by bar charts of ...
Visual acuity is measured by the smallest letters that can be distinguished on a chart and is governed by the anatomical spacing of the mosaic of sensory elements on the retina. Yet spatial distinctions can be made on a finer scale still: misalignment of borders can be detected with a precision up to 10 times better than visual acuity, as ...
A related phenomenon is the visual system's capacity to calculate time-to-contact (TTC) of an approaching object from the rate of optical expansion – a useful ability in contexts ranging from driving a car to playing a ball game. However, the calculation of TTC is, strictly speaking, a perception of velocity rather than depth.
The fibers from the retina run along the optic nerve to nine primary visual nuclei in the brain, from which a major relay inputs into the primary visual cortex. A fundus photograph showing the back of the retina. The white circle is the beginning of the optic nerve. The optic nerve is composed of retinal ganglion cell axons and glia.
Beyond its literal sense concerning the visual system, the term scotoma is also used metaphorically in several fields, including neurology, neuropsychology, psychology, philosophy, and politics. The common theme of all the figurative senses is of a gap not in visual function but in the mind's perception, cognition, or world view.