Printer Friendly Format

BLINKING

NORMAL BLINKING

Blinking is a physiologic response which involves relaxation of the levator muscle (which opens the eyelids) with simultaneous contraction of the palpebral portion of the orbicularis oculi muscles (which closes the eyelids).

Normal or spontaneous blink rates vary from twelve to twenty blinks per minute. The blink rate in infants is much lower and may normally be only one or two blinks per minute.

BLINKING IS A NORMAL FUNCTION THAT HELPS TO REMOVE FOREIGN MATERIAL

Blinking can be divided into spontaneous, reflex, and voluntary blinking. Heightened levels of awareness or increased anxiety may increase the blink rate whereas decreased spontaneous blink rates may result from anything that will depress the central nervous system.

Blinking helps to cleanse the cornea and anterior segment of the eye. Rapid phase cinematography has demonstrated that the blink closes the eyelids from their lateral most portions toward the nasal portion thus causing a squeegee effect pushing tears and foreign material toward the nasolacrimal collecting system, near the nasal insertion of the eyelids.

Blinking also serves to wet the cornea and redistribute the tear film over it. This serves to create an optically smooth interface between the corneal surface and the surrounding atmosphere.

DECREASED BLINKING

Decrease in spontaneous blinking may occur with central nervous depression, either drug related or when a patient is in a coma. It is also noted in some diseases of the central nervous system such as Parkinson's Disease.

Reflex blinking may also be decreased. Defects that reduce the sensation of the cornea, such as herpes keratitis or a congenital lack of sensation (Riley-Day Syndrome), may cause decreased intensity of afferent impulses or decreased stimulation for reflex blinking.

If the decreased corneal sensation is accompanied by other cranial nerve defects, the brain stem and the region of the cerebello-pontine angle, should be investigated.

Decreased intensity of strength of the blink may be caused by seventh cranial nerve dysfunction. This may be due to Bell's Palsy or to injury of the seventh cranial nerve. In either of these situations, the afferent or sensory pathway remains intact, but the efferent pathway to close the lids is abnormal. (The patient will usually have corneal sensation.)

EXCESSIVE BLINKING

Excessive blinking may be related to either increased duration of lid closure or it may be due to an increased rate of blinking. Prolonged lid closure may be related to blepharospasm (which is very uncommon in children), central nervous system stimulation, and tardive dyskinesia (a side effect of some tranquilizers). Increased blinking rate may be due to irritative lesions in the central nervous system (meningitis) or ocular abnormalities.

Some ocular abnormalities which are associated with increased blinking rate are: albinism, corneal dystrophy, achromatopsia, and any condition that may cause diffraction of light striking the cornea, such as a corneal abrasion or a corneal scratch caused by a foreign body lodged under the eyelid. An allergy may cause blinking with or without sensations of ocular irritation. The allergic blinking pattern can exhibit an increased frequency for lid closure and /or "rolling" of the eyes.

EXCESSIVE BLINKING IN CHILDREN IS FREQUENTLY DUE TO A NERVOUS TIC

Finally, the most common cause of excessive blinking is behavior abnormalities commonly referred to as tics. These habits usually last for 2 - 3 months or so and are not associated with ocular pathology. These common tic disorders are transient and usually last less than a year. These repetitive activities are self limited and are not associated with vocal or other complex involuntary activity. Tics may be accompanied by functional eyelid pulling, squinting, or rapid voluntary blinking.

TOURETTE SYNDROME

This rare syndrome will usually develop in childhood (mean age 7 years old) and is a life long disorder. In most families this will follow an autosomal dominant hereditary pattern of inheritance modified by environmental factors. This syndrome comprises multiple complex motor and / or vocal tics which occur concurrently.

EVALUATION

To evaluate the blinking, a complete history should be obtained. The drug history should include use of phenothiazines (antiemetics), since these may cause tar dive dyskinesia.
David Taylor, M.D. has outlined some helpful questions in his book "Pediatric Ophthalmology".

1. Is it the blink or is it the duration of the blink that is abnormal?

2. Does the blink occur at any specific situation, time of day, or in bright sunlight? What is its relation to stress or a particular social situation? Does the blink occur in the wind or when the child is attempting to look at something?

3. Is the eye or eyelid ever red or painful? Is the eyelid being irritated by a condition such as blepharitis?

4. Does the entire lid twitch or just a portion of the lid (myokymia)? Do other facial muscles also twitch (hemifacial spasm)? Are there accompanying eye movement disorders Are there eyelid disorders or any signs of central nervous disease?

5. Is there a history of behavioral or psychological problems?

6. What is the duration of symptoms? (Tourettes Syndrome should become a consideration when the blinking persists more than a year and is associated with other signs such as vocal tics and other complex movements.)

The physical exam should include a measurement of visual acuity to exclude large degrees of astigmatism or other undetected refractive errors.

The external eyelids should be examined. The lid margins and the bulbar and palpebral conjunctiva of the lower and upper lids should be inspected. When palpebral blinking is associated with allergy the conjunctiva is irritated or has a cobble stone appearance. When this is observed, the search for an irritant or an allergen should be investigated. This is best done by a review of exposure or activity earlier in the day or during the previous day. If there is suspicion of a foreign body, fluorescein stain of the cornea can be applied and a cobalt blue light can be used to detect any corneal surface irregularities. A careful search for a foreign body or eyelash in the cul de sac or on the cornea should be done in any patient with monocular blinking or squinting.

In older children, examination using a slit lamp may be helpful. The cornea should be checked for sensation prior to installation of any anesthetic drops.

Other systemic symptoms should be looked for. Are there signs or symptoms of a seizure disorder or a neurological problem? If it is possible, refraction and a cover test should be performed to test for refractive errors and to exclude strabismus.

Some forms of achromatopsia may be associated with blinking and blepharospasm. Color vision testing will help to diagnose this defect. Children with albinism will have increased ERG responses and although the diagnosis is obvious on external examination, this test may be performed in very select situations.

In most children, the examination will be normal and if it is, reassurance can be given to the parent. In such cases, the blinking is usually a self-limited problem, due to a tic. Blinking will last for several weeks or for a few months and will then disappear. Sometimes all that is necessary is to reassure the child (and parent) that the eye exam is normal. The child should be reassured that the tic will gradually subside following the exam. It is best not to be confrontational to the child, which is, telling him or her that there is no problem or that you shouldn't be doing this. Rather, give the child reassurance and let the child eliminate the blinking at his or her own volition. If there is an allergic component, elimination of the allergen or reducing the exposure to the allergen is suggested. IF THERE ARE SIGNS OF AN ALLERGY - TREATMENT IS INDICATED. Eye drops such as a topical antihistamine or Mast Cell Stabilizer may help. Use of mild topical corticosteroids four times a day may be helpful. Tics will increase with anxiety and if this is a component, a source of the problem may be looked for.

Brabec, Levin and Nelson have examined causes for functional blinking in childhood and found that new situations such as a new sibling, beginning reading in school, a new school situation, or a death in the family, were common problems that were associated with the onset of excessive blinking. Similar observations were made by Catalano, Trevisani and Simon when they investigated functional eyelid pulling in children. Further information on the differential diagnosis can be gained from Ellis's chapter in the book, Decision Making in Pediatric Ophthalmology edited by Gerhard Cibis, M.D.

Pediatric Ophthalmology and Strabismus, Inc.