**Core Concept**
Radial keratotomy is a surgical procedure used to correct myopia (nearsightedness) by altering the shape of the cornea. The goal is to reduce the refractive power of the cornea, allowing light to focus further back in the eye and reducing the severity of myopia.

**Why the Correct Answer is Right**
Radial keratotomy involves making small radial incisions in the cornea, which causes the cornea to flatten and decrease its refractive power. This procedure is typically performed for mild to moderate myopia, as it can effectively reduce the refractive error and improve vision. The radial incisions disrupt the normal curvature of the cornea, allowing the surrounding corneal tissue to collapse and flatten, thereby reducing the refractive power.

**Why Each Wrong Option is Incorrect**
* **Option A:** Radial keratotomy is not typically used for astigmatism, as it can actually worsen this condition by creating irregular corneal curvature. Astigmatism correction often requires different surgical procedures, such as astigmatic keratotomy or LASIK with astigmatism correction.
* **Option B:** Radial keratotomy is not a procedure for presbyopia, which is age-related loss of near vision due to decreased accommodation. Presbyopia correction often involves multifocal intraocular lenses or other surgical procedures.
* **Option C:** Radial keratotomy is not used for hyperopia (farsightedness), as it can actually worsen this condition by reducing the refractive power of the cornea. Hyperopia correction often requires different surgical procedures, such as hyperopic LASIK or phakic intraocular lenses.

**Clinical Pearl / High-Yield Fact**
Radial keratotomy is a relatively old surgical procedure, and it has largely been replaced by newer techniques like LASIK and PRK, which offer more precise and effective correction of refractive errors.

**Correct Answer: C. Myopia**