Everyone blinks. The average adult blinks 14 to 17 times a minute, or about 13,440 to 16,320 times a day while awake.1 When we don’t blink as often as we should, our eyes may feel dry, irritated, heavy, or tired, and our overall vision can be impacted.
In addition to maintaining the integrity of the corneal surface, blinking also helps us process visual input. How can an action that takes less than a second have such a significant role in our vision?
The mechanics of blinking
Blinking is important for the maintenance of the ocular surface as it provides mechanical protection, activates the lacrimal pump, stimulates expression of the meibomian glands, and distributes the tear film.2
Blinks may be categorized as spontaneous, voluntary, or reflexive:
- Spontaneous blinks: Occur in the absence of any obvious stimulus. They are the most common form of blinking and are responsible for maintaining the integrity of the ocular surface and tear film stability.3
- Voluntary blinks: These are intentionally performed eyelid movements to close the eyes. They are used for a variety of purposes, including communication and alleviating ocular discomfort.3
- Reflex blinks: Occur involuntarily in response to threatening or startling stimuli, including irritants on the ocular surface, bright lights, or loud sounds.4
How do we define a successful blink?
Efficient blinking requires a combination of all three types of blinking, but spontaneous blinking is the most important for maintenance of the tear film and corneal surface. Blink behavior can be difficult to assess clinically as it varies based on factors like air temperature, humidity, and movement, as well as fatigue, mood, and interest in an activity.
An efficient blink should have the following characteristics:5
- Complete and full
- Soft, relaxed, and light
- Brief, quick, and rapid
If any of these characteristics are missing, there can be detrimental impacts to the ocular surface and, subsequently, on visual comfort. For example, if the blink is not complete, then there is a portion of the cornea that is left nearly constantly exposed to the environment, resulting in disruption of the tear film and symptoms of ocular irritation.
Conditions that affect blinking
There are several systemic and ophthalmic conditions that can influence blinking.
Digital eye strain
With our increasing reliance on screen time for work and school, as well as our increased desire to spend our leisure time on screens, “computer vision syndrome” is becoming a more recognized condition. Frequent screen use has been associated with an increase in incomplete blinks and a decrease in blink rate.6
Dry eye
Symptoms of dry eye disease (DED) cause an increase in blink rate due to an increase in reflex blinking. As tear breakup time decreases and/or tear film hyperosmolarity increases to the point of awareness, reflex blinking becomes more critical for the maintenance of the ocular surface.7,8
Corneal abrasions
The mechanical force of blinking can cause increased pain and discomfort for patients suffering from corneal abrasions. This is why bandage contact lenses, which provide a barrier between the eyelid and the cornea, are an important tool in the treatment of corneal abrasions.9
Conjunctivitis
Discomfort caused by conjunctivitis, be it viral, bacterial, or allergic, generally leads to an increase in blink rate; however, the discomfort caused by blinking itself can also lead to a reduction in blink rate.10
Blepharospasm
Blepharospasm is an involuntary eyelid closure due to excessive intermittent or sustained contraction of the orbicularis oculi muscle, which causes excessive blinking and difficulty opening the eyelid.11 Patients who suffer from blepharospasm are thus left unable to fully open their affected eye(s) during an episode.
Exotropia
Patients with intermittent exotropia often use blinking as a way to improve their control over their deviation and re-establish binocular vision. In one study of children with exotropia, 43% reported blinking to control their eyes and 40% reported blinking a lot.12
The role of blinking in visual information processing
While maintaining the ocular surface is critical to eye health, research has found that humans blink more frequently than is needed to sufficiently maintain the tear film. These extra blinks may have another purpose—processing visual input.
One study found improvement in performance in object recognition tasks following eye blinks. The researchers hypothesized that this is due to changes in large-scale network activity after blinking, leading to an “attentional refresh.” Blinking allows for a release of attention, freeing the individual to switch their attention to another stimulus.13
Improvement in visual information processing through blinking may seem counterintuitive, as blinking temporarily occludes the retina and prevents the eye from acquiring visual information. Research has shown, however, that the modulation of input to the retina during a blink actually improves contrast sensitivity due to luminance changes.
Blinking allows us to better evaluate visual input at low spatial frequencies, which researchers believe may outweigh the loss of visual input during the blink.14
Final takeaways
As often as we blink throughout the day, the benefits of blinking are probably not at the forefront of most people’s minds. Our role as primary eyecare providers is to educate our patients on the importance of blinking, not only for their ocular surface, but also for their visual information processing.
When patients have abnormal blinking habits, it is important to determine the cause and determine what intervention, if any, is needed to maximize their blinking efficiency and give them their best visual prognosis.
