What Is the Inferior Oblique?

Inferior oblique muscle (IO) see extraocular muscles. It starts from the lateral side of the orbital plane tear groove of the maxilla and ends at the striated muscle on the sclera behind the equator outside the eyeball. The total length is about 37 mm, which is the shortest extraocular muscle. From the shallow fossa at the frontal medial angle of the inferior orbital wall and the lacrimal sac equivalent to the periosteum on the outside of the nasolacrimal duct orifice, it walks outwards and backwards. Widen to 9 to 10 mm to the attachment point. The average muscle width is 9.4 mm. The middle section intersects with the lower rectus muscle below the inferior rectus muscle, extending outward to the back of the eye equatorial and attached to the outer side of the posterior pole of the eye, with a shallow width of 9.4 mm, a tendon length of 1 mm, and the distance of the front attachment point. The limbus is 12 mm, which is 2 mm higher than the lower edge of the external rectus muscle, and is 51 ° from the visual axis. It is innervated by the oculomotor nerve, and 12 mm from the posterolateral side of the inferior rectus muscle is the innervation point.

Inferior oblique muscle (IO) see extraocular muscles. It starts from the lateral side of the orbital plane tear groove of the maxilla and ends at the striated muscle on the sclera behind the equator outside the eyeball. The total length is about 37 mm, which is the shortest extraocular muscle. From the shallow fossa at the frontal medial angle of the inferior orbital wall and the lacrimal sac equivalent to the periosteum on the outside of the nasolacrimal duct orifice, it walks outward and backward. The muscle at the beginning is oval, 4-5 mm in diameter, and gradually Widen to 9 to 10 mm to the attachment point. The average muscle width is 9.4 mm. The middle section intersects with the lower rectus muscle below the inferior rectus muscle, extending outward to the back of the eye equatorial and attached to the outer side of the posterior pole of the eye, with a shallow width of 9.4 mm, a tendon length of 1 mm, and the distance of the front attachment point The limbus is 12 mm, which is 2 mm higher than the lower edge of the external rectus muscle, and is 51 ° from the visual axis. It is innervated by the oculomotor nerve, and 12 mm from the posterolateral side of the inferior rectus muscle is the innervation point.

Chinese name

Inferior oblique

Foreign name

inferior oblique muscle, IO

Location

Anterior medial

Function

Pulling the eyeballs, turning the pupil upward

Inferior oblique muscle function

When the first eye position, the main role is external rotation, and the secondary role is upturn and external rotation; when the inward rotation of the eyeball is 51 ° from the first eye position, only the upward rotation effect is played; When the eye position is 39 °, external rotation and slight external rotation can be exerted.

Inferior oblique muscle related diseases-inferior oblique hyperfunction

Clinical manifestation of inferior oblique muscle

Rotational strabismus refers to the abnormal rotation of the eyeball around the visual axis. It is usually the force between the internally rotating muscles (upper obliques, upper rectus muscles) and the externally rotating muscles (lower obliques, lower rectus muscles). Caused by imbalance. Common congenital factors include: congenital superior oblique paralysis and primary inferior oblique hypertrophy. In addition, optical factors such as oblique axis astigmatism and structural abnormalities of Pully can cause eyeball rotation. Studies have shown that subjective rotation can only be detected by 6-year-olds who develop oblique hyperfunction after visual maturity. When the patient's eyes are looking inward, the upward deflection is obvious. The latter said that the eye in the inward position exhibits a characteristic symptom of hanging (more inward). When the patient turned out, the degree of upward deflection was reduced.

Inferior oblique muscle examination method

(1) Eye movement inspection: According to Maruo's classification method of inferior oblique hypertrophy, the degree of inferior oblique hypertrophy is divided into three degrees: when the inclination of the inferior oblique is upward, the degree of upward rotation is stronger than the contralateral eye. When turning in, an upturn is defined as ++, and the eye position in front of it is higher than the contralateral eye as +++.

(2) Simultaneous machine examination: For patients with binocular monocular function and normal retina correspondence, cross picture examination can be used to measure not only the horizontal and vertical slopes but also the rotation slope. In addition, ordinary grade I paintings (lions and cages, cars and doors, etc.) are used. The measurement of the V sign is measured by turning the picture up and down by 25 ° to measure the horizontal prism power, and the difference between the two values is calculated as the value of the V sign.

(3) Double Markov rod inspection: Subjective rotational strabismus degree can be quantitatively measured through the double Markov rod inspection. Also use a point light source to place a foot away in front of the eyes. The patient wears special glasses. The lens is a glass rod placed vertically. The frame is marked with a scale. One of the lenses has a triangular prism to see both eyes. The effect of line separation. People without rotation strabismus should see two parallel lines. For patients with rotation strabismus with binocular monovision, the two lines are not parallel. Adjust the knob on the frame to make the two lines parallel, and the measured degree is rotation. Slope.

Choice of inferior oblique surgery

(1) Large-angle exotropia, vertical strabismus is less than 5 , surgery for unilateral inferior oblique hyperfunction is not considered, and only exotropia is treated.

(2) Exotropia is accompanied by inferior oblique hyperfunction, vertical strabismus of 10 -20 , and surgical treatment of inferior oblique disconnection (no patients with more than 20 in vertical oblique strabismus were found).

(3) Patients with exotropia accompanied by V sign were treated with bilateral inferior oblique muscle broken key + exotropia surgery.

(4) In patients with exotropia accompanied by inferior oblique dysfunction and vertical dissociative strabismus (DVD), the inferior oblique is used for transposition. According to different DVD levels, choose different inversion methods (inferior oblique receding and inferior oblique transposition).