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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)
Photic retinopathy is damage to the eye's retina, particularly the macula, from prolonged exposure to solar radiation or other bright light, e.g., lasers or arc welders.The term includes solar, laser, and welder's retinopathy and is synonymous with retinal phototoxicity. [1]
The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye. [3] In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at.
This can occur in low-light conditions, in the dark, or when the visual system amplifies light perception. In these cases, visual snow is a normal reaction of the body, related to the way photoreceptors (rods) and neurons respond to weak or insufficient stimuli. [citation needed]
This leads to the human eye being unable to resolve high spatial frequencies in low light since the observer is spatially averaging the light signal. [ 9 ] Another reason that vision is poor under scotopic vision is that rods, which are the only cells active under scotopic vision, converge to a smaller number of neurons in the retina.
Symptoms typically appear gradually over 5 to 20 minutes and generally last less than 60 minutes, leading to the headache in classic migraine with aura, or resolving without consequence in acephalgic migraine. [3] For many sufferers, scintillating scotoma is first experienced as a prodrome to migraine, then without migraine later in life ...
Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." [ 1 ] It is a disorientation -, vertigo -, and nausea -inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves .
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 ...