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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.
The underlying mechanism is believed to involve excessive excitability of neurons in the right lingual gyrus and left anterior lobe of the cerebellum. Another hypothesis proposes that visual snow syndrome could be a type of thalamocortical dysrhythmia and may involve the thalamic reticular nucleus (TRN). A failure of inhibitory action from the ...
Ocular hypertension is the presence of elevated fluid pressure inside the eye (intraocular pressure), usually with no optic nerve damage or visual field loss. [1] [2]For most individuals, the normal range of intraocular pressure is between 10 mmHg and 21 mmHg. [3]
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 ]
For eye pressures, a value of 28 hPa (21 mmHg) above atmospheric pressure 1,010 hPa (760 mmHg) is often used, with higher pressures leading to a greater risk. [2] [26] However, some may have high eye pressure for years and never develop damage. [2] Conversely, optic nerve damage may occur with normal pressure, known as normal-tension glaucoma. [27]
Intra-ocular pressure ISNT: Inferior, Superior, Nasal, Temporal rule used to assess optic disc appearance K: Keratometry OS oculus sinister (left eye) LHyperT or LHT: Left hypertropia LHypoT: Left hypotropia LO: Lenticular opacity L/R FD: L/R fixation disparity L/R: L hyperphoria Left ET: Left esotropia LVA: Low vision aid MDU: Mallett distance ...
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One example of a pressure phosphene is demonstrated by gently pressing the side of one's eye and observing a colored ring of light on the opposite side, as detailed by Isaac Newton. [ 7 ] [ 8 ] [ 9 ] Another common phosphene is "seeing stars" from a sneeze , laughter, a heavy and deep cough, blowing of the nose , a blow on the head or low blood ...