glare

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glare

(glār),
A sensation caused by brightness within the visual field that is sufficiently greater than the luminance to which the eyes are adapted; results in annoyance, discomfort, and decreased visual performance.

glare

(glār) discomfort in the eye and depression of central vision produced when a bright light enters the field of vision, particularly when the eye is adapted to dark. It is direct g. when the image of the light falls on the fovea and indirect g. when it falls outside the fovea.

glare

a strong, dazzling light that may cause discomfort to the eye. Visual problems that result from glare often involve inadequate lighting conditions; they particularly affect individuals with cataracts or other disease conditions. The condition is relieved somewhat by using incandescent rather than fluorescent lighting, wearing a visor, wearing special antiglare lenses, and using a matte-black cardboard typoscope for reading words on a glaring white paper.

glare

A visual condition in which the observer feels either discomfort and/or exhibits a lower performance in visual tests (e.g. visual acuity or contrast sensitivity). This is produced by a relatively bright source of light (called the glare source) within the visual field. A given bright light may or may not produce glare depending upon the location and intensity of the light source, the background luminance, the state of adaptation of the eye or the clarity of the media of the eye.
direct glare Glare produced by a source of light situated in the same or nearly the same direction as the object of fixation.
disability glare Glare which reduces visual performance without necessarily causing discomfort.
discomfort glare Glare which produces discomfort without necessarily interfering with visual performance.
eccentric glare See indirect glare.
indirect glare Glare produced by an intense light source situated in a direction other than that of the object of fixation. Syn. eccentric glare.
glare source See glare.
glare tester An instrument for measuring the effect of glare on visual performance. There exist several (e.g. Brightness Acuity Tester (BAT), Miller-Nadler Glare Tester, Optec 1500 Glare Tester). Glare testing is valuable in patients with corneal and lenticular opacities before and after surgery and in elderly patients in whom adaptation to glare is usually more difficult. The Miller-Nadler Glare Tester consists of a glare source surrounding a Landolt C. The instrument contains 19 black Landolt C, all of the same size, 6/120 (or 20/400). Each Landolt C is presented in one of four orientations and from the highest to the lowest contrast at which the subject can no longer judge in which direction the letter appears. The contrast threshold is expressed in percentage disability glare.The
Brightness Acuity Tester (BAT) is a standardized glare source of light. It is presented in a hemisphere held over one eye. The light source can subtend a visual angle of 8 to 70 degrees at a vertex distance of 12 mm. The patient is asked to read a visual acuity chart through a small aperture in the hemisphere. The chart can be a low-contrast or high-contrast log MAR visual acuity chart or, for example, the Pelli-Robson contrast sensitivity chart.
veiling glare Glare caused by scattered light and producing a loss of contrast.
References in classic literature ?
The unveiled, low sun glared angrily from a chaotic sky upon a confused and tremendous sea dashing itself upon a coast.
At the sound of its discharge, the doctor rose up erect, like a spectre, and glared around him.
Hearing this, the King glared at his Counselor with a furious expression and tugged at his own long white whiskers until he pulled them so hard that he yelled with pain.
Numa glared intently at the quiet body in the dust.
She had on her shoulders a garment red with the blood of men, and terribly she glared and gnashed her teeth.
Hollow from hunger, Sheeta, the panther, glared greedily at the tempting meat so close at hand, but the sight of the great bulls beyond gave him pause.