Blinking

Blinking is the rapid closing and reopening of the eyelids. It protects the eye from injury, helps maintain a healthy ocular surface, and spreads the tear film to keep the eye lubricated and free of debris.

Most blinking is spontaneous (basal blinking) and occurs without conscious control to maintain tear distribution. In adults, basal blinks occur about 10–15 times per minute at rest, with frequency often decreasing during intense visual tasks and increasing in dry or windy environments or when fatigued. Voluntary blinking can be deliberately initiated for expression or to momentarily interrupt vision. Reflex blinking is triggered by threats such as a foreign object, bright light, or air movement and tends to be rapid and protective.

Anatomy and control: The eyelids are opened by the levator palpebrae superioris (innervated by the oculomotor nerve) and closed by the orbicularis oculi (innervated by the facial nerve). Blinking is coordinated by brainstem circuits, with higher-level input from the frontal lobe during voluntary blinking. The tear film, spread by blinking, consists of lipid, aqueous, and mucin layers. Tears are produced by the lacrimal glands, and the meibomian glands provide lipids that reduce tear evaporation, supporting surface health between blinks.

Clinical relevance: Abnormal blinking patterns can indicate ocular surface disease, fatigue, or neurological conditions. Excessive blinking may accompany dry eye, irritation, or tic disorders, while reduced blinking can occur with fatigue or certain neurological impairments. Disorders affecting eyelid movement, such as blepharospasm or ptosis, can impair blinking and eyelid function.