The eye blinks when the tear film breaks up and it feels dryness. Frequent blinking — blinking more often than about every 10 seconds, or blinking constantly — can be a sign of a foreign body in the eye, a feeling of a foreign body in the eye, dryness, scratchiness, grittiness, or a short tear break-up time that is a sign of evaporative dry eye.
References
Relation between blink frequency and break-up time?
Prause JU, Norn M.
Acta ophthalmologica
1987 Feb;65(1):19-22.
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