**Core Concept**
Amblyopia, also known as lazy eye, is a vision development disorder in which the brain favors one eye over the other due to unequal visual input, leading to reduced vision in the affected eye. This condition often results from anatomical or physiological abnormalities in the eye, such as strabismus (misaligned eyes), cataracts, or refractive errors.

**Why the Correct Answer is Right**
The correct answer accurately describes amblyopia as a disorder caused by abnormal visual input during critical periods of visual development, which can lead to permanent vision loss if left untreated. In amblyopia, the brain suppresses the signal from the affected eye, resulting in reduced visual acuity. This suppression can occur due to factors such as strabismus, where the eyes are not aligned, causing the brain to favor the eye with the clearer image.

**Why Each Wrong Option is Incorrect**
* **Option A:** Amblyopia is not caused by a lack of visual input, but rather unequal visual input.
* **Option B:** Amblyopia is not a result of a single episode of visual deprivation, but rather prolonged periods of unequal visual input during visual development.
* **Option C:** Amblyopia is not a condition that can be easily reversed with corrective lenses alone, as it requires specific treatments such as patching or vision therapy to re-establish normal visual input.

**Clinical Pearl / High-Yield Fact**
Amblyopia is a treatable condition, especially when identified and treated early in life. Patching the stronger eye to force the brain to rely on the weaker eye is a common treatment approach. Early detection and treatment can help restore normal vision in the affected eye.

**Correct Answer: D. Amblyopia is a disorder caused by abnormal visual input during critical periods of visual development, leading to permanent vision loss if left untreated.**