**Core Concept**
The underlying principle being tested here is the concept of **crossed fibers or crossed nerve supply** in the optic nerve, which plays a crucial role in the phenomenon being described.

**Why the Correct Answer is Right**
In this scenario, the injury to one eye (the injured eye) causes a loss of vision in the opposite (healthy) eye due to the crossed fibers in the optic nerve. This phenomenon occurs because the nerve fibers from each eye are mixed together in the optic chiasm, allowing for some degree of cross-talk between the two eyes. When the injured eye is stimulated, it can still send signals to the brain via the intact nerve fibers, but the signals from the healthy eye are blocked due to the injury. After corneal grafting, the injured eye is able to send clear signals, and the patient regains vision in that eye.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the phenomenon being tested. The phenomenon is not related to a difference in refractive power between the two eyes.
* **Option B:** This option is incorrect because it is not a recognized medical term, and it does not accurately describe the phenomenon being tested.
* **Option C:** This option is incorrect because it implies that the injury is affecting the healthy eye directly, which is not the case.

**Clinical Pearl / High-Yield Fact**
This phenomenon is a classic example of a **crossed nerve supply**, which can lead to unexpected consequences in patients with eye injuries.

**Correct Answer: C. Heterotropia**