Thickest poion of sclera is ?
**Core Concept**
The sclera is the white, fibrous, protective layer of the eyeball, comprising about 80% of its surface area. Its thickness varies across different regions, with the thickest portion providing optimal structural support to the eye.
**Why the Correct Answer is Right**
The thickest portion of the sclera is the **posterior sclera**, which is located at the back of the eye, near the optic nerve. This region is thicker due to the presence of a dense layer of collagen fibers and elastin, providing strength and elasticity to the sclera. The posterior sclera also contains the optic nerve and the blood vessels that supply the eye.
**Why Each Wrong Option is Incorrect**
* **Option A:** The **anterior sclera** is actually thinner than the posterior sclera, as it is less dense and more prone to injury.
* **Option B:** The **equatorial region** of the sclera is thicker than the anterior sclera but still thinner than the posterior sclera.
* **Option C:** The **limbus**, the border between the sclera and the cornea, is a transitional zone and not the thickest portion of the sclera.
**Clinical Pearl / High-Yield Fact**
The sclera's thickness varies across different regions, and its thickest portion provides optimal structural support to the eye. Remember the acronym **POSTERIOR** to recall the thickest portion of the sclera: P - posterior, O - optic nerve, S - sclera, T - thickness, E - elasticity, R - region, I - important, O - optic nerve, R - region.
**Correct Answer: C. The equatorial region is not the thickest portion of sclera.