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Visual snow: dynamic, continuous, tiny dots observed across the entire visual field at any time of the day, regardless of lighting conditions, persisting for more than three months. The dots are usually black/gray on a white background and gray/white on a black background; however, they can also be transparent, white flashing, or colored.
Photopsias is defined as an effect on the vision that causes appearances of anomalies in the vision. Photopsias usually appear as: flickering lights; shimmering lights; floating shapes; moving dots; snow or static; Photopsias are not generally a condition on their own, but a symptom of another condition.
In the test, the person looks with each eye separately at the small dot in the center of the grid. Patients with macular disease may see wavy lines or some lines may be missing. Amsler grids are supplied by ophthalmologists, optometrists or from web sites, and may be used to test one's vision at home. The original Amsler grid was black and white.
Eye examination for visual acuity. Visual acuity is a measure of the spatial resolution of the visual processing system. VA, as it is sometimes referred to by optical professionals, is tested by requiring the person whose vision is being tested to identify so-called optotypes – stylized letters, Landolt rings, pediatric symbols, symbols for the illiterate, standardized Cyrillic letters in ...
Color blindness is usually an inherited problem or variation in the functionality of one or more of the three classes of cone cells in the retina, which mediate color vision. [2] The most common form is caused by a genetic condition called congenital red–green color blindness (including protan and deutan types), which affects up to 1 in 12 ...
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Close-up of an LCD, showing a dead green subpixel as a black rectangle. A defective pixel is a pixel on a liquid crystal display (LCD) that is not functioning properly. The ISO standard ISO 13406-2 distinguishes between three different types of defective pixels, [1] while hardware companies tend to have further distinguishing types.
An ophthalmoscopic view of the retina showing advanced signs of diabetic retinopathy including two pale cotton wool spots. Cotton wool spots are opaque fluffy white patches on the retina of the eye that are considered an abnormal finding during a funduscopic exam (also called an ophthalmoscopic exam). [1]