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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 ...
Light sensitivity or photosensitivity refers to a notable or increased reactivity to light. Apart from vision , human beings have many physiological and psychological responses to light. In rare individuals an atypical response may result in serious discomfort, disease, or injury.
The first symptoms most people notice are difficulty reading fine print, particularly in low light conditions, eyestrain when reading for long periods, blurring of near objects or temporarily blurred vision when changing the viewing distance. Many extreme presbyopes complain that their arms have become "too short" to hold reading material at a ...
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The retina lines the inside of the eye. It is light-sensitive and communicates visual messages to the brain. If the retina detaches, it moves and shifts from its normal position. This can cause photopsia, but can also cause permanent vision loss. Medical attention is needed to prevent vision loss.
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 ...
Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light.In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity.
The human eye uses three types of cones to sense light in three bands of color. The biological pigments of the cones have maximum absorption values at wavelengths of about 420 nm (blue), 534 nm (bluish-green), and 564 nm (yellowish-green). Their sensitivity ranges overlap to provide vision throughout the visible spectrum.