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.
