Disability ceificate for poor vision if 4/60, is impairment percentage of:

**Core Concept**
The World Health Organization (WHO) uses the International Classification of Functioning, Disability and Health (ICF) to classify and measure health and disability. The ICF defines impairment as a significant deviation or loss of psychological, physiological, or anatomical structure or function. Impairment is further classified into different domains, including vision.

**Why the Correct Answer is Right**
Impairment in vision is measured using the LogMAR (Logarithm of the Minimum Angle of Resolution) visual acuity chart. However, for the purpose of disability certification, the Snellen visual acuity chart is often used. The Snellen chart uses a logarithmic scale, with a normal visual acuity of 6/6. Impairment percentage is calculated based on the distance visual acuity in the better eye with the best possible correction. A visual acuity of 4/60 corresponds to a significant impairment, and the impairment percentage is calculated accordingly.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a specific percentage or calculation method.
**Option B:** This option is incorrect because it is not a recognized method for calculating impairment percentage.
**Option C:** This option is incorrect because it is a common distractor and does not provide a specific percentage or calculation method.

**Clinical Pearl / High-Yield Fact**
When calculating impairment percentage, it's essential to use the Snellen visual acuity chart and the ICF classification system. A visual acuity of 4/60 corresponds to a significant impairment, and the impairment percentage is calculated accordingly.

**Correct Answer:** 70%.