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Nyctalopia (/ ˌ n ɪ k t ə ˈ l oʊ p i ə /; from Ancient Greek νύκτ-(núkt-) 'night' ἀλαός (alaós) 'blind, invisible' and ὄψ (óps) 'eye'), [1] also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases.
How these symptoms affect the patient depends on to which organs or body parts blood supply is inhibited. Typical symptoms of Flammer syndrome are cold hands or feet, low blood pressure, occasional white and red patches on the face or neck, and migraine-like pain or a feeling of pressure behind the upper eyelid.
This is the reverse of a redout, or a reddening of the vision, which is the result of negative g-forces caused by performing an outside loop, that is by pushing the nose of the aircraft down. Redouts are potentially dangerous and can cause retinal damage and hemorrhagic stroke .
Effect of night blindness. Left: good night vision. Right: nightblind. Insufficiency of adaptation most commonly presents as insufficient adaptation to dark environment, called night blindness or nyctalopia. [35] The opposite problem, known as hemeralopia, that is, inability to see clearly in bright light, is much rarer.
The ANS controls some of the body's natural processes such as sweating, skin flushing and pupil response to stimuli. [1] Individuals with this syndrome have an absence of sweat skin flushing unilaterally, usually on one side of the face, arms and chest. It is an autonomic disorder that may occur at any age.
Ocular ischemic syndrome is the constellation of ocular signs and symptoms secondary to severe, chronic arterial hypoperfusion to the eye. [1] Amaurosis fugax is a form of acute vision loss caused by reduced blood flow to the eye; it may be a warning sign of an impending stroke, as both stroke and retinal artery occlusion can be caused by thromboembolism due to atherosclerosis elsewhere in the ...
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 ]
Angle-closure glaucoma should be considered if there is painful loss of vision with a red eye, nausea or vomiting. [4] The eye pressure will be very high typically greater than 40 mmHg. [5] Emergent laser treatment to the iris may prevent blindness. [4]