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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 ...
uncontrollable squinting/closing of eyes; light sensitivity (photophobia) squinting/eyes closing during speech; uncontrollable eyes closing shut (rare instances completely causing blindness) In addition, in some patients, the dystonic spasms may sometimes be provoked by certain activities, such as talking, chewing, or biting.
Presbyopia is a physiological insufficiency of optical accommodation associated with the aging of the eye; it results in progressively worsening ability to focus clearly on close objects. [4] Also known as age-related farsightedness [5] (or as age-related long sight in the UK [6]), it affects many adults over the age of 40. A common sign of ...
Photopsia is the presence of perceived flashes of light in the field of vision. It is most commonly associated with: [4] posterior vitreous detachment; migraine aura (ocular migraine / retinal migraine) migraine aura without headache; scintillating scotoma; retinal break or detachment; occipital lobe infarction (similar to occipital stroke)
Most older adult humans lose photopic spatial contrast sensitivity. Adults in their 70s tend to require about 30–60% more contrast to detect high spatial frequencies than adults in their 20s. [3] The human eye uses scotopic vision under low-light conditions (luminance level 10 −6 to 10 −3.5 cd/m 2), and mesopic vision in intermediate ...
Typical measurements of light have used a Dosimeter. Dosimeters measure an individual's or an object's exposure to something in the environment, such as light dosimeters and ultraviolet dosimeters. In order to specifically measure the amount of light entering the eye, personal circadian light meter called the Daysimeter has been developed. [11]
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Visual perception is the ability to interpret the surrounding environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and mesopic vision (twilight vision), using light in the visible spectrum reflected by objects in the environment.