How Fast Is a Blink of an Eye?

Definition

A blink is when a person closes and opens her eyelids one or more times. This particular action may be reflexive, such as when the body feels the eyes need moisturizing, or conscious, such as when a person flutters his eyelashes by blinking fairly rapidly.

Purpose

The purpose of blinking is to keep the eyes healthy, clean and properly moisturized. The act of blinking spreads tears over the eyes and makes sure that they are always kept wet. Tears are made from the small, lacrimal glands in the eye, and they drain out through the nasolacrimal duct into the nose.

Speed

The human eye can blink much faster than a second, and, in fact, it's perfectly possible to blink several times in a single second. On average, a human eye takes between 300 and 400 milliseconds to complete a single blink. That's roughly between three-tenths and four-tenths of a second. So, logically speaking, a person may blink two and three times every second and barely notice it because the blink takes so little time.

Slow Factors

The 300 to 400 milliseconds for a blink is only an average human speed. This time can be affected--usually negatively--by a variety of factors. If there is any foreign substance in the eye, if the person blinking is sick or if there is an injury to the eye, a person's blinking time will be much slower. Additionally, factors such as how tired a person is or if he is on any medications can also slow down blinking time.

Fast Factors

Just as there are factors that will slow down a person's blinking, there are factors that may speed it up. Younger tend to blink faster than older people. Physical health may also figure in, as a healthier body will function more rapidly. Also, if a person is on drugs that would be classified as 'uppers,' such as cocaine or even caffeine, the speed of her blinks will likely increase.