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Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or colored dots across the whole visual field. [7] [4] Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches.
Green flash occurs because the atmosphere causes the light from the Sun to separate, or refract, into different frequencies. Green flashes are enhanced by mirages, which increase refraction. A green flash is more likely to be seen in stable, clear air, when more of the light from the setting sun reaches the observer without being scattered.
The primary causes include post-cataract surgery, certain medications, and, less commonly, neurological or ophthalmological conditions. Post-cataract surgery is a common cause, as replacing the natural lens with a synthetic one increases exposure to blue light, leading to temporary blue-tinted vision. This effect usually resolves as the eye adapts.
Illusory palinopsia is often worse with high stimulus intensity and contrast ratio in a dark adapted state.Multiple types of illusory palinopsia often co-exist in a patient and occur with other diffuse, persistent illusory symptoms such as halos around objects, dysmetropsia (micropsia, macropsia, pelopsia, or teleopsia), Alice in Wonderland Syndrome, visual snow, and oscillopsia.
A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red. Color phi phenomenon: The color phi phenomenon is a perceptual illusion in which a disembodied perception of motion is produced by a succession of still images. Contingent perceptual ...
Peduncular hallucinosis (PH) is a rare neurological phenomenon that causes vivid visual hallucinations that typically occur in dark environments and last for several minutes. Unlike some other kinds of hallucinations, the hallucinations that patients with PH experience are very realistic, and often involve people and environments that are ...
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. Procedures may include laser treatment, freezing, or surgery.
In teichopsia, migraine sufferers may see patterns that look like the shape of the walls of a star fort. As the scotoma area expands, some people perceive only a bright flickering area that obstructs normal vision, while others describe seeing various patterns. Some describe seeing one or more shimmering arcs of white or colored flashing lights.