What condition results from dysfunction of the orbicularis oculi muscle?

The condition resulting from dysfunction of the orbicularis oculi muscle is lagophthalmos. This muscle is responsible for closing the eyelids and facilitating blinking, which is essential for spreading tears across the cornea and keeping the eye moist. When the orbicularis oculi muscle does not function properly, it can lead to an inability to fully close the eyelids, resulting in lagophthalmos. This condition can expose the eye to environmental irritants, increase the risk of corneal damage, and contribute to dryness and discomfort.

In contrast, ptosis refers to the drooping of the upper eyelid, often due to issues with the levator palpebrae muscle, rather than the orbicularis oculi. Entropion is characterized by the inward rolling of the eyelid margin, which is not directly associated with dysfunction of the orbicularis oculi but rather with changes in the connective tissue or muscle tone in the eyelid. Exophthalmos refers to the protrusion of the eyeball, usually due to conditions like thyroid disease, and does not involve the orbicularis oculi muscle directly affecting eyelid closure.