What condition is characterized by a spasm of the orbicularis oculi muscle?

Blepharospasm is characterized by the involuntary spasm of the orbicularis oculi muscle, leading to excessive blinking and difficulty keeping the eyes open. This condition is often associated with irritation, inflammation, or various ocular diseases, and can manifest as a protective reflex response to light, wind, or foreign body sensation in the eye.

In blepharospasm, the spasms can be sustained or intermittent and may severely impact the affected individual's vision and quality of life. This condition is distinct from other eyelid conditions as it primarily involves muscle activity rather than structural abnormalities of the eyelids or surrounding tissues.

Other options represent different eyelid disorders: blepharitis involves inflammation of the eyelid margins, ectropion refers to the outward turning of the eyelid, and entropion is characterized by the inward turning of the eyelid. These conditions affect the eyelid's positioning and may lead to complications such as irritation or infection, but they do not involve the spasmodic muscle contractions seen in blepharospasm.