Visual acuity (VA) commonly refers to the clarity of vision, but technically rates a person's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye influence the sharpness of an image on its retina. Neural factors include the health and functioning of the retina, of the neural pathways to the brain, and of the interpretative faculty of the brain.
The most commonly referred-to visual acuity is distance acuity or far acuity (e.g., "20/20 vision"), which describes someone's ability to recognize small details at a far distance. This ability is compromised in people with myopia, also known as short-sightedness or near-sightedness. Another visual acuity is near acuity, which describes someone's ability to recognize small details at a near distance. This ability is compromised in people with hyperopia, also known as long-sightedness or far-sightedness.
A common optical cause of low visual acuity is refractive error (ametropia): errors in how the light is refracted in the eyeball. Causes of refractive errors include aberrations in the shape of the eyeball or the cornea, and reduced ability of the lens to focus light. When the combined refractive power of the cornea and lens is too high for the length of the eyeball, the retinal image will be in focus in front of the retina and out of focus on the retina, yielding myopia. A similar poorly focussed retinal image happens when the combined refractive power of the cornea and lens is too low for the length of the eyeball except that the focused image is behind the retina, yielding hyperopia. Normal refractive power is referred to as emmetropia. Other optical causes of low visual acuity include astigmatism, in which contours of a particular orientation are blurred, and more complex corneal irregularities.
Refractive errors can mostly be corrected by optical means (such as eyeglasses, contact lenses, and refractive surgery). For example, in the case of myopia, the correction is to reduce the power of the eye's refraction by a so-called minus lens.
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
The human eye is a sensory organ, part of the sensory nervous system, that reacts to visible light and allows humans to use visual information for various purposes including seeing things, keeping balance, and maintaining circadian rhythm. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer layers, such as the outermost, white part of the eye (the sclera) and one of its inner layers (the pigmented choroid) keeping the eye essentially light tight except on the eye's optic axis.
Peripheral vision, or indirect vision, is vision as it occurs outside the point of fixation, i.e. away from the center of gaze or, when viewed at large angles, in (or out of) the "corner of one's eye". The vast majority of the area in the visual field is included in the notion of peripheral vision. "Far peripheral" vision refers to the area at the edges of the visual field, "mid-peripheral" vision refers to medium eccentricities, and "near-peripheral", sometimes referred to as "para-central" vision, exists adjacent to the center of gaze.
Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. It results in decreased vision in an eye that typically appears normal in other aspects. Amblyopia is the most common cause of decreased vision in a single eye among children and younger adults. The cause of amblyopia can be any condition that interferes with focusing during early childhood.
Introduction aux phénomènes propagatifs dans les circuits hydrauliques, calculs de coups de béliers, comportement transitoire d'aménagements hydroélectriques, simulation numériques 1D du comportement
This course focuses on the production of utopian scenarios using experimental composition techniques. By means of digital montage, the fictitious scenes are meaningfully conveyed in a series of images
Basic knowledge ofthe classical non-destructive testing methods as they are used today in industrial applications and the advanced
(mosily imaginé) technologies used for the analysis of materials and
Explores hydraulic machines under transient conditions and hydroacoustic applications for hydroelectric installations, covering equilibrium chimneys, diaphragm cavitation, and turbine stability.
Understanding the brain requires an integrated understanding of different scales of organisation of the brain. This Massive Open Online Course (MOOC) will take the you through the latest data, models
Understanding the brain requires an integrated understanding of different scales of organisation of the brain. This Massive Open Online Course (MOOC) will take the you through the latest data, models
Using batteries of visual tests, most studies have found that there are only weak correlations between the performance levels of the tests. Factor analysis has confirmed these results. This means that a participant excelling in one test may rank low in ano ...
Using batteries of visual tests, most studies have found that there are only weak correlations between performance levels of tests in healthy young adults. Factor analysis has confirmed these results. This means that a participant excelling in one test may ...
EPFL2024
, , ,
Electrical stimulation of the visual nervous system could improve the quality of life of patients affected by acquired blindness by restoring some visual sensations, but requires careful optimization of stimulation parameters to produce useful perceptions. ...