**Core Concept:** Blindness is a visual impairment that significantly affects a person's daily life and quality of life. The World Health Organization (WHO) defines blindness based on visual acuity.

**Why the Correct Answer is Right:** According to the WHO, blindness is defined as the visual acuity of less than 3/60, which corresponds to counting fingers (CF) at a distance of 6 meters. This means that the individual cannot discern the shapes and details of objects at this distance, significantly affecting their ability to perform daily tasks and activities.

**Why Each Wrong Option is Incorrect:**

A. **3/60**: This option is incorrect because it is the threshold for severe visual impairment, not blindness. Severe visual impairment (SVI) is defined as visual acuity of 3/60 to 6/60, allowing the individual to recognize faces but not read or write.

B. **Counting fingers (CF)**: Although this is the correct answer in terms of visual acuity, the distance is incorrect. The correct distance for counting fingers is 6 meters, not the provided 1 meter.

C. **Visual acuity of 6/180**: This option is incorrect because it represents moderate visual impairment, not blindness. Moderate visual impairment is defined as visual acuity of 6/18 to 3/60, allowing the individual to recognize faces but not read or write.

D. **Visual acuity of 6/6**: This option is incorrect because it represents normal vision, with visual acuity of 6/6 indicating that an individual can read letters on an eye chart at a distance of 6 meters.

**Clinical Pearl:** It is essential for healthcare professionals to accurately diagnose and define visual impairments, as it has significant implications for patient care, rehabilitation, and access to appropriate resources and support.

**Correct Answer:** B. Counting fingers (CF) at a distance of 6 meters.

Blindness, according to the WHO, is defined as visual acuity of less than 3/60, which corresponds to the inability to discern counting fingers (CF) at a distance of 6 meters. This definition ensures that the individual cannot recognize objects or faces and significantly affects their daily functioning, justifying the need for rehabilitation and appropriate resources.