blink

blink

the involuntary movement of one or both eyelids of both eyes simultaneously. The frequency varies between species. Cats blink the least, with the possible exception of owls. In birds it is the lower eyelid which is moved up to meet the upper lid. In mammals the upper eyelid is moved down to meet the lower lid. The blink is a part of several reflexes including the palpebral, conjunctival and menace reflexes.

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blink reflex

see blink response.

blink response

absent in lesions of the ophthalmic branch of the trigeminal nerve. Called also blink reflex.

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blink 

A temporary closure of the eyelids (usually of both eyes). Blinks are usually involuntary but may be voluntary. The frequency of blinking is conditioned by a number of external and internal factors, e.g. glare, wind, emotion, attention, tiredness, etc. Normal blink rate is about 10 blinks per minute, although there are wide variations. The duration of a full blink is approximately 0.3-0.4 s. Blink rates are often altered with contact lens wear and in some diseased states (e.g. chalazion, Graves' disease). See corneal reflex; wink.