Blink, incomplete

The diagnosis of lagophthalmos or incomplete blink is usually made based on the patient s symptoms, slit-lamp examination, and gross observation during a blink. Patients usually complain of ocular irritation, which is worse upon awakening. Biomicroscopy reveals SPK over the inferior portion of the cornea or over the area of exposure. The patient should be asked to blink while at the slit lamp they should be closely examined outside of the slit lamp, which will often reveal the exposure or occasionally a femily member will confirm that the patient sleeps with his or her eyes open. 

The seventh cranial nerve is responsible for eyelid closure during the blink reflex. Partial or complete disturbance of cranial nerve VII can interrupt these impulses, resulting in incomplete lid closure. Loss of muscular tone can also lead to ectropion, disruption of the lacrimal pump, and ultimately impaired tear drainage. 

Evaporative loss can also occnr from abnormal ocular surfece exposure, due to incomplete blink, nocturnal lagophthalmos, exophthalmos, proptosis, cranial nerve VII palsy, lid retraction, or other eyelid position and apposition disorders. Contact lenses may also contribute to an increased tear evaporation rate. 

Numerous neurologic and mechanical fectors may result in chronic corneal drying due to infrequent or incomplete blinking or inadequate eyelid closure (lagophthalmos). The resultant irritation to the corneal tissue is known as exposure keratopathy. 

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