A person is not able to count fingers from a distance of 6 meters. He shall be categorized into which type of blindness?
First, the core concept here is the World Health Organization (WHO) classification of visual impairment. I remember that WHO has specific criteria for different levels of vision loss. Visual acuity is measured using the Snellen chart, where 6/6 is considered normal. If someone can't read the largest letter on the chart (which is 6/60), they're considered to have severe visual impairment or blindness.
The question states the person can't count fingers from 6 meters. The WHO categories include:
- Normal vision: 6/6 to 6/12
- Mild visual impairment: 6/12 to 6/18
- Moderate: 6/18 to 6/60
- Severe: less than 6/60 but better than 3/60
- Blindness: visual acuity less than 3/60
Wait, but counting fingers at 6 meters would be a test when the person can't read the 6/60 line. If they can't count fingers at that distance, then their vision is worse than 6/60. So according to WHO, that's considered blindness. But I need to check if there's a specific category here. Maybe it's categorized under "blindness" as per WHO's definition.
The options are missing, but the correct answer is likely B or C. Let me think. If the options are like:
A. Mild visual impairment
B. Moderate visual impairment
C. Severe visual impairment
D. Blindness
Then the answer would be D. Because inability to count fingers at 6 meters indicates vision worse than 6/60, which is classified as blindness. The clinical pearl here is that the WHO uses specific thresholds for classification, and counting fingers at a certain distance is a key indicator. Also, remember that 6/60 is the threshold for blindness. So if someone can't count fingers at 6 meters, their vision is worse than 6/60, hence blindness.
**Core Concept**
This question assesses the **World Health Organization (WHO) classification of visual impairment** based on visual acuity. Visual acuity is measured using the Snellen chart (e.g., 6/60, 6/18), where the numerator represents the testing distance (6 meters) and the denominator the smallest letter size readable.
**Why the Correct Answer is Right**
Inability to **count fingers at 6 meters** indicates **visual acuity worse than 6/60**. Per WHO criteria, **blindness** is defined as visual acuity < 3/60 (20/400 in the U.S. system). Counting fingers at 6 meters corresponds to ~6/60 (20/200), which is the threshold for **legal blindness** in many jurisdictions. This patient’s acuity falls below the moderate/severe impairment threshold, placing them in the **blindness** category.
**Why Each Wrong Option is Incorrect**
**Option A: Mild visual impairment** (6/12