Blinking is a normal and physiologically important phenomenon. It is infrequent in newborn babies, hence their wide-eyed stare. The frequency slowly increases as the nervous system matures. Adults blink about 14-17 times a minute.
But why do we blink? The importance of blinking includes its protective role in preventing the entry of dust or any object into the eye, as well as shutting out too bright light from the unprepared eye. It also plays an essential role in keeping the eye moist and healthy, by spreading the tear film over the whole exposed surface of the eye. The rate of blinking increases when you’re talking, when you’re nervous, in pain, or when you’re exposed to very bright lights. Frequent blinking may also occur as a nervous tic in some people.
Causes and risk factors
Excessive blinking is caused by over-stimulation of the blinking reflex. This is most commonly due to a foreign body in the eye. This can be as simple as an ingrown eyelash rubbing against the front of the eyeball. Thus anything which causes a corneal abrasion causes excessive blinking and watering in an attempt to wash out the foreign body. Excessive blinking may also be caused by allergic reactions causing watering, itching and roughening of the conjunctiva.
In many children, especially boys, around the age of 5, incessant blinking becomes a habit. It may be an attention-getting device, but usually stops on its own in a few months. If there are other associated symptoms such as red or watering eyes, pain or swelling, prompt evaluation and treatment are required to correct the underlying cause.
Other causes include:
- dry eye
- blepharitis (inflammation of the eyelid)
- uveitis (inflammation of the iris)
- myopia (short sightedness)
- bright light
- eye strain
- long hours in front of a flickering monitor
Blepharospasm is a disease condition causing rapid and involuntary blinking. In this condition, abnormal nervous stimulation is the root cause. This results in spasmodic contraction of the ocular muscles without any obvious cause. Blepharospasm is classified as one type of abnormal muscle tone, or dystonia. Eye dystonia is commonly seen between the ages of 50 and 70 years, and may be of varying severity.
Blepharospasm due to dystonia is sometimes accompanied by other facial movements like sudden grimaces and rolling of the eyes. It is then called Meige’s syndrome. Other symptoms of this special condition include:
- twitching of the eyelids
- a feeling of heaviness around the eyes
- drooping of the eyelids
- swelling around the eye
- dry or gritty feeling of the eye
- excessive sensitivity to bright light or sunshine.
All these symptoms may be exaggerated and thus become more obvious in the presence of fatigue, anxiety, bright light, wind or dust, or while driving.
Other diseases involving excessive blinking
There are other disease states associated with excessive blinking. These include nervous system disorders involving movement such as:
- Tourette syndrome
- Parkinson’s disease
- Tardive dyskinesia caused by certain psychiatric medications
These are suspected when there are serious symptoms other than blinking, such as:
- numbness or weakness on one side of the body
- disorientation or confusion
- difficulties with speech or vision
- a sudden intense headache or severe vomiting
- other muscular symptoms
The presence of these medical conditions is confirmed by:
- a careful history, including the kind of medications the person is on
- physical examination
- imaging studies such as MRI or CT scans.
When does excessive blinking become abnormal?
Excessive blinking may be thought to be abnormal if:
- it affects normal life
- it interferes with normal vision, as when one is driving
- it doesn’t stop within a few hours
- it is associated with other symptoms, as above
Blepharospasm is treated with botox injections to relax or paralyze the muscles involved. This gives significant relief in more than 90% of patients. The condition itself persists over the long term in 75% of patients, but need not interfere with normal life activities unless it is of very severe degree.
[Futher Reading: Blinking]