**Core Concept**
The National Programme for Control of Blindness (NPCB) classifies visual impairment based on visual acuity in the better eye. This classification is crucial for planning and allocating resources for blindness prevention and management programs.

**Why the Correct Answer is Right**
Visual acuity is measured in logarithmic units (logMAR) and expressed as a fraction, with 6/6 being normal vision. According to the World Health Organization (WHO) classification, a visual acuity of 3/60 is considered severe visual impairment (or low vision), and a visual acuity of 6/60 is considered moderate visual impairment. The NPCB uses these WHO criteria to classify visual impairment. In this case, the patient's better eye has a visual acuity of 6/60, which falls into the moderate visual impairment category.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a valid classification under the NPCB or WHO criteria.
**Option B:** This option is incorrect because the NPCB does not classify visual impairment based on age.
**Option C:** This option is incorrect because the NPCB classifies visual impairment based on visual acuity, not the type of eye disease or condition.

**Clinical Pearl / High-Yield Fact**
The NPCB uses the WHO classification to categorize visual impairment, which is essential for planning and allocating resources for blindness prevention and management programs.

**Correct Answer: D.**