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Pressure phosphenes can persist briefly after the rubbing stops and the eyes are opened, allowing the phosphenes to be seen on the visual scene. Hermann von Helmholtz and others have published drawings of their pressure phosphenes. One example of a pressure phosphene is demonstrated by gently pressing the side of one's eye and observing a ...
Some may be individual red blood cells swollen due to osmotic pressure. Others may be chains of red blood cells stuck together; diffraction patterns can be seen around these. [2] Others may be "coagula of the proteins of the vitreous gel, to embryonic remnants, or the condensation round the walls of Cloquet's canal " that exist in pockets of ...
Visual snow is a phenomenon where a person perceives visual disturbances, such as fine graininess or "static," in their field of vision. This can occur in low-light conditions, in the dark, or when the visual system amplifies light perception.
Closed-eye hallucinations and closed-eye visualizations (CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They should not be confused with phosphenes , perceived light and shapes when pressure is applied to the eye's retina, or some other non-visual external cause stimulates the eye.
Intraocular pressure varies throughout the night and day. The diurnal variation for normal eyes is between 3 and 6 mmHg and the variation may increase in glaucomatous eyes. During the night, intraocular pressure may not decrease [ 17 ] despite the slower production of aqueous humour. [ 18 ]
Amaurosis fugax (Ancient Greek: ἀμαύρωσις, amaurosis meaning 'darkening', 'dark', or 'obscure', Latin: fugax meaning 'fleeting') is a painless temporary loss of vision in one or both eyes. [ 3 ]
He documented it in his 90-year-old grandfather [21] who was nearly blind from cataracts in both eyes. [7] After Bonnet's grandfather received bilateral cataract surgery, his vision evolved from slightly better to complete deterioration over time. [6] It was around this period that his visual hallucinations started. [6]
The red reflex (also called the fundal reflex) refers to the reddish-orange reflection of light from the back of the eye, or fundus, observed when using an ophthalmoscope or retinoscope. The red reflex may be absent or poorly visible in people with dark eyes, and may even appear yellow in Asians or green/blue in Africans. [1]