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Nyctalopia (/ ˌ n ɪ k t ə ˈ l oʊ p i ə /; from Ancient Greek νύκτ-(núkt-) 'night' ἀλαός (alaós) 'blind, invisible' and ὄψ (óps) 'eye'), [1] also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
Visual snow is a phenomenon where a person perceives visual disturbances, such as fine graininess or "static," in their field of vision. This can occur in low-light conditions, in the dark, or when the visual system amplifies light perception.
Averted vision works because there are virtually no rods (cells which detect dim light in black and white) in the fovea: a small area in the center of the eye. The fovea contains primarily cone cells, which serve as bright light and color detectors and are not as useful during the night. This situation results in a decrease in visual ...
A phosphene is the perception of light without light actually entering the eye, for instance caused by pressure applied to the closed eyes. A phenomenon that could be entoptical if the eyelashes are considered to be part of the eye is seeing light diffracted through the eyelashes.
Scotopic vision occurs at luminance levels of 10 −3 [7] to 10 −6 [citation needed] cd/m 2.Other species are not universally color blind in low-light conditions. The elephant hawk-moth (Deilephila elpenor) displays advanced color discrimination even in dim starlight.
Glare can be generally divided into two types, discomfort glare and disability glare. [1] Discomfort glare is a psychological sensation caused by high brightness (or brightness contrast) within the field of view, which does not necessarily impair vision. [2]
That may mean lashing out when dinner isn’t what they thought it would be or getting frustrated when they can’t find something. ... “You can see [the person with dementia] change at a ...
The opposite problem, known as hemeralopia, that is, inability to see clearly in bright light, is much rarer. The fovea is blind to dim light (due to its cone-only array) and the rods are more sensitive, so a dim star on a moonless night must be viewed from the side, so it stimulates the rods. This is not due to pupil width since an artificial ...