WHO definition of blindness
**Core Concept**
The World Health Organization (WHO) defines blindness as a visual impairment that severely affects an individual's daily life. This definition is based on the visual acuity of an individual, which is a measure of their ability to see objects clearly at a distance.
**Why the Correct Answer is Right**
The WHO definition of blindness is a visual acuity of less than 3/60 in the better eye with the best possible correction, which is the ability to see objects clearly at a distance of 3 meters. This definition takes into account the impact of visual impairment on an individual's quality of life, rather than just their visual acuity. The measurement of visual acuity is typically done using a Snellen chart, which is a standardized tool for assessing visual acuity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the WHO definition of blindness is based on visual acuity, not visual field defects. While visual field defects can significantly impact an individual's daily life, they are not the primary factor in the WHO definition of blindness.
**Option B:** This option is incorrect because the WHO definition of blindness does not specify a particular age at which visual impairment is considered blindness. Visual impairment can occur at any age, and the WHO definition is intended to be universal and applicable across different age groups.
**Option C:** This option is incorrect because the WHO definition of blindness is based on visual acuity, not the presence of eye diseases or conditions. While certain eye diseases or conditions can cause visual impairment, the WHO definition is focused on the severity of the visual impairment, rather than its cause.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the WHO definition of blindness is based on visual acuity, and not just the presence of visual impairment. This definition is critical for understanding and addressing the global burden of blindness, as well as for providing appropriate rehabilitation and support to individuals with visual impairment.
**Correct Answer:** C.