## Core Concept
Anisometropia refers to a condition where there is a significant difference in the refractive power between the two eyes. This condition can lead to difficulties in binocular vision and may cause problems such as amblyopia if not corrected properly.

## Why the Correct Answer is Right
The term "Anisometropia" comes from the Greek words "aniso" meaning unequal and "metron" meaning measure. In ophthalmology, it specifically refers to a type of refractive error where one eye has a significantly different refractive power compared to the other eye. This can manifest as different levels of myopia, hyperopia, or astigmatism between the two eyes.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because anisometropia specifically refers to the difference in refractive error between the two eyes, not the same refractive error in both eyes.
- **Option B:** This option is incorrect because isometropia would imply the same or equal refractive error in both eyes, which is the opposite of anisometropia.
- **Option C:** While this option might seem related, anisometropia specifically refers to the condition of having different refractive powers in the eyes, not just any difference in vision.

## Clinical Pearl / High-Yield Fact
A key clinical consideration in anisometropia is the potential for amblyopia, particularly if the condition is not corrected early in life. Significant anisometropia can lead to difficulties with binocular vision, including stereopsis, and may require specialized treatment such as corrective lenses, and in some cases, refractive surgery.

**Correct Answer:** D. Different refractive error in both eyes.