While the famous saying ‘in the blink of an eye’ refers to the fastness of things, some questions come to the curious minds,
How many times do we blink our eyes in a minute, in one hour or in a day? Why do we do that? Why do we even have eyelids?
Scientific studies show that we normally blink our eyes (both eyes at a time) 15-20 times per minute, around 1,200 times per hour, which comes around 28,800 times in a day. We do it more often if there is wind blowing towards our eyes or if there are foreign particles in the eye (dust/insects), or if the eyes are infected by certain diseases. We blink so many times that during the time that we are awake, 10% of the time we have our eyes closed.
We do it because we need to lubricate and moisturize the visible part of our eyeball and the cornea, and to protect it from dust, wind friction or over-bright light.
It is done by a complex mechanism in our eyes called as the lacrimal apparatus. To make it simple, let’s begin with the tear glands. We have glands just above our eyeball in the front called as lacrimal glands. They continuously secrete lacrimal fluid, commonly known as tears (when the fluid overflows our eyes). To spread this secretion evenly we have a conjunctival sac over the visible part of the eyeball, continued on the inner side of the eyelids, this sac is open (incomplete) when the eyes are open and closes (completes) when the eyes are closed. It is when the eyes are blinked again and again the fluid is evenly distributed on the eyeball (just like spreading butter on bread). That is why we have eye lids, so that they can do the even distribution of the lacrimal fluid on the eye ball and also protect the eyes from foreign particles.
The excess fluid is drained in the nose by a canal that connects the conjunctival sac on the eye to wall of nose, from where it is distributed in the nose as well. That’s why we have runny nose when we cry.
While blinking is natural and healthy, deliberate closure of one eye (winking), might not be so!
– Dr. Vaseemraja
Assistant Professor Anatomy