**Core Concept**
Isochromatic charts, also known as isochromatic or Ishihara charts, are a type of test used to assess color vision. They contain dots of different colors that, when viewed from a distance, form a number or shape that is invisible to people with certain types of color vision deficiency.

**Why the Correct Answer is Right**
The correct answer is related to the use of isochromatic charts in screening for color vision deficiency, particularly in individuals with red-green color blindness. The charts contain dots of red and green colors that are arranged in a specific pattern, and when viewed by a person with normal color vision, the dots blend together to form a number or shape. However, people with red-green color blindness may see the dots as a different number or shape due to their inability to distinguish between red and green colors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because isochromatic charts are not primarily used for detecting visual field defects or assessing visual acuity.
**Option B:** This option is incorrect because isochromatic charts are not used for detecting peripheral vision or assessing depth perception.
**Option C:** This option is incorrect because isochromatic charts are not used for detecting cataracts or assessing refractive errors.

**Clinical Pearl / High-Yield Fact**
Isochromatic charts are a widely used screening tool for color vision deficiency, and a common cause of color vision deficiency is genetic, with red-green color blindness being the most common type.

**Correct Answer:** D. Screening for color vision deficiency.