Dow nward and outward movement of eyeball is caused by
**Core Concept**
The downward and outward movement of the eyeball is a complex process involving the coordinated action of several extraocular muscles. This movement is essential for the accurate alignment of the visual axis with the target object in space.
**Why the Correct Answer is Right**
The downward and outward movement of the eyeball is primarily caused by the action of the inferior oblique muscle. The inferior oblique muscle originates from the maxillary bone and inserts into the sclera of the eyeball. When it contracts, it rotates the eyeball downward and outward, allowing for the accurate alignment of the visual axis with the target object in space. This movement is also facilitated by the action of the lateral rectus muscle, which abducts the eyeball and helps to maintain its outward rotation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the superior oblique muscle primarily causes the downward and inward movement of the eyeball, not downward and outward.
* **Option B:** This option is incorrect because the medial rectus muscle primarily causes the adduction of the eyeball, not downward and outward movement.
* **Option D:** This option is incorrect because the superior rectus muscle primarily causes the elevation of the eyeball, not downward and outward movement.
**Clinical Pearl / High-Yield Fact**
The inferior oblique muscle is responsible for the downward and outward movement of the eyeball, and its dysfunction can lead to hypertropia and esotropia of the affected eye. This is an important clinical correlation to remember when evaluating patients with eye movement disorders.
**Correct Answer:** C.