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Some mental control can be exerted over these closed-eye visualizations, but it usually requires a bit of relaxation and concentration to achieve. [1] [2] When properly relaxed, it is possible to cause regions of intense black, bright white or even colors such as yellow, green, or pink to appear in the noise. These regions can span the entire ...
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.
Prosopometamorphopsia is a visual disorder characterized by altered perceptions of faces. In the perception of a person with the disorder, facial features are distorted in a variety of ways including drooping, swelling, discoloration, and shifts of position. Prosopometamorphopsia is distinct from prosopagnosia, which is characterised by the ...
According to WebMD, cicada eggs are a food source for oak leaf itch mites — tiny arachnids that aren't even a quarter of a millimeter in length and that are "invisible to the naked eye." Each ...
Scleral tattooing is the practice of tattooing the sclera, or white part, of the human eye. Rather than being injected into the tissue, the dye is injected between two layers of the eye, then gradually spreads. The process remains uncommon due to professionals' discomfort performing the procedure [ 1] and is illegal in the American states ...
Scintillating scotoma is a common visual aura that was first described by 19th-century physician Hubert Airy (1838–1903). Originating from the brain, it may precede a migraine headache, but can also occur acephalgically (without headache), also known as visual migraine or migraine aura. [ 4]
Entoptic phenomena (from Ancient Greek ἐντός (entós) 'within' and ὀπτικός (optikós) 'visual') are visual effects whose source is within the human eye itself. (Occasionally, these are called entopic phenomena, which is probably a typographical mistake.) In Helmholtz 's words: "Under suitable conditions light falling on the eye ...
An afterimage is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological ( palinopsia ). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical ...