What is the palpebral fissure function?
This narrow, crescent-shaped fold of conjunctiva, located in the medial canthus, allows for lateral movement of the eye without stretching the bulbar conjunctiva.
Why do palpebral fissures occur?
Congenital dysmorphisms The chromosomal conditions trisomy 9 and trisomy 21 (Down syndrome) can cause the palpebral fissures to be upslanted, whereas Marfan syndrome can cause a downslant. An increase in vertical height can be seen in genetic disorders such as cri-du-chat syndrome.
Which cranial nerve affects palpebral fissures?
Touching the medial canthus of the palpebral fissure stimulates the ophthalmic branch of the trigeminal nerve which runs into the skull through the orbital fissure and once inside the brainstem triggers a motor response via the facial nerve.
What muscle opens the palpebral fissure?
In small animals, the size of the palpebral fissure primarily depends on normal tone in the levator palpebrae superioris muscle. This muscle is innervated by somatic efferent fibers of the oculomotor nerve (CN III), providing for elevation of the upper eyelid.
What is the meaning of palpebral?
Definition of palpebral : of, relating to, or located on or near the eyelids.
How is palpebral fissure measured?
The palpebral fissure and the greatest width of the vermilion border of the upper lip were measured with a rigid plastic ruler marked with 1 mm intervals. The measurement of the palpebral fissure was taken with the ruler at the greatest horizontal axis between the eye endocanthion and its exocanthion.
What genetic disorders cause palpebral slant?
General Discussion. Pallister W syndrome is a rare genetic disorder characterized by unusual facial features such as clefting of the palate and the upper lip, a broad flat nose, widely spaced slanted eyes, and/or downslanting eyelid folds (palpebral fissures).
Does palpebral fissure increase with age?
They found that the palpebral fissure width increased by more than 10% between 12 and 25 years, but decreased by nearly 10% between 45 and 85 years (P = 0.01).
How do you test for CN 3?
Inability to follow and object in direction of CN III (the quickest test is to observe upward gaze which is all CN III; the eye on the affected side does not look upward) Inability to open the eyelid. CN III dysfunction causes the eyelid on the affected side to become “droopy”.
What is lid lag hyperthyroidism?
Lid lag can be measured by comparing the upper eyelid position in downgaze to its position in primary gaze relative to a fixed point like the pupil. 1. Lid lag happens when there is increased contraction of the levator palpebrae muscles of the eyelids. 6. Lid lag subsides when the hyperthyroidism is treated.
What nerve closes the eyelid?
The oculomotor nerve is the third cranial nerve (CN III). It allows movement of the eye muscles, constriction of the pupil, focusing the eyes and the position of the upper eyelid.
What is palpebral edema?
Definition. Edema in the region of the eyelids. [ from HPO]
What is a palpebral fissure?
Palpebral Fissure. The palpebral fissure is the area between the open eyelids. Although numerous variations exist in the positional relationship of the lid margins to the limbus, generally the upper lid just covers the superior limbus when one’s eyes are open and looking straight ahead.
What causes narrow palpebral fissure in horses?
In the horse and farm animals, a narrow palpebral fissure occurs with facial nerve dysfunction (loss of function of the levator anguli oculi medialis muscle). An elevated third eyelid will be apparent with sympathetic denervation, as well as secondary to atrophy of the muscles of mastication.
What is a hemifacial fissure?
Hemifacial spasm—A narrowed palpebral fissure occurs with spasm of the facial muscles on one side. A small palpebral fissure occurs following extensive atrophy of the muscles of mastication, as the eye retracts into the orbit.