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Rapid flickers in intensity of light may trigger or aggravate photosensitive epilepsy, epileptic seizure, or migraine headaches. [4] Conditions that may include sensitivity to light include vertigo and chronic fatigue syndrome. Controlled application of artificial light can be used in a program of light therapy to treat some disorders.
The normal human observer's relative wavelength sensitivity will not change due to background illumination under scotopic vision. The wavelength sensitivity is determined by the rhodopsin photopigment. This is a red pigment seen at the back of the eye in animals that have a white background to their eye called Tapetum lucidum.
Photophobia is a medical symptom of abnormal intolerance to visual perception of light. [1] As a medical symptom, photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical sensitivity of the eyes, [2] though the term is sometimes additionally applied to abnormal or irrational fear of light, such as ...
Photosensitivity occurs in multiple species including sheep, bovine, and horses.They are classified as primary if an ingested plant contains a photosensitive substance, like hypericin in St John's wort poisoning and ingestion of biserrula (Biserrula pelecinus) [3] in sheep, or buckwheat plants (green or dried) in horses.
There are two luminous efficiency functions in common use. For everyday light levels, the photopic luminosity function best approximates the response of the human eye. For low light levels, the response of the human eye changes, and the scotopic curve applies. The photopic curve is the CIE standard curve used in the CIE 1931 color space.
With the eye generally profusely watering, the type of tears being produced have little adhesive property. Water or saline eye drops tend therefore to be ineffective. Rather a 'better quality' of tear is required with higher 'wetting ability' (i.e. greater amount of glycoproteins ) and so artificial tears (e.g. viscotears ) are applied frequently.
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The human eye can function from very dark to very bright levels of light; its sensing capabilities reach across nine orders of magnitude. This means that the brightest and the darkest light signal that the eye can sense are a factor of roughly 1,000,000,000 apart. However, in any given moment of time, the eye can only sense a contrast ratio of ...