**Core Concept**
The Amsler grid test is a simple, non-invasive tool used to detect and monitor visual field defects and maculopathy in patients with macular degeneration, diabetic retinopathy, or other conditions affecting the central vision.

**Why the Correct Answer is Right**
The Amsler grid consists of a grid of horizontal and vertical lines that intersect at right angles, with a central dot. Patients with visual field defects or maculopathy will report seeing distortions, missing areas, or wavy lines in the grid. This is because the macula, the area at the back of the eye responsible for central vision, is affected by the underlying condition. The Amsler grid test relies on the patient's subjective report of any abnormalities in the grid, which can indicate macular dysfunction.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the Amsler grid test, which is primarily used for detecting visual field defects and maculopathy.
**Option B:** This option is incorrect as the Amsler grid test is not used to measure visual acuity, which is typically assessed using Snellen charts.
**Option C:** While the Amsler grid test can be used to monitor changes in visual field defects over time, it is not primarily used for detecting amblyopia.

**Clinical Pearl / High-Yield Fact**
The Amsler grid test is a simple, yet effective tool for detecting maculopathy and visual field defects, and should be part of the routine eye examination for patients at risk of these conditions.

**Correct Answer: D. Detecting visual field defects and maculopathy.**