Blinking
Blinking
Blinking (/ˈblɪŋkɪŋ/) is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi, not the full open and close. It is an essential function of the eye that helps spread tears across and remove irritants from the surface of the cornea and conjunctiva.
Etymology
The term "blink" comes from the Old English "blencan", meaning to move suddenly or to shift out of place. It is related to the Middle English "blenchen" and the Old Norse "blinka", both of which also mean to move suddenly or to flinch.
Function
Blinking serves various purposes:
- It keeps the eyes lubricated by spreading tears over its surface.
- It helps protect the eye from foreign bodies and bright light.
- It can also serve as a non-verbal communication signal (e.g., winking).
Frequency
The typical blinking rate is around 15-20 times per minute, although this can vary depending on factors such as fatigue, eye irritation, and concentration.
Related Terms
- Blepharospasm: An abnormal, involuntary blinking or spasm of the eyelids.
- Ptosis (eyelid): Drooping or falling of the upper or lower eyelid.
- Lacrimal apparatus: The physiological system containing the orbital structures for tear production and drainage.
- Meibomian gland: The tiny oil glands which line the margin of the eyelids (the edges which touch when the eyelids are closed).
External links
- Medical encyclopedia article on Blinking
- Wikipedia's article - Blinking
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