In the ninth revision of the international classification of diseases, ‘Visual impairment’ is a visual acuity in the better eye of:
**Core Concept**
The ninth revision of the international classification of diseases (ICD-9) provides a standardized way of categorizing and reporting diseases, including visual impairments. Visual acuity is a crucial factor in assessing the severity of vision problems. In the ICD-9, visual impairments are classified based on the level of visual acuity in the better eye.
**Why the Correct Answer is Right**
Visual impairment is defined as a visual acuity of less than 6/18 in the better eye. This classification is based on the Snellen visual acuity chart, where 6/18 is the minimum standard for normal vision. A visual acuity of 6/18 or better indicates normal vision, while a visual acuity of less than 6/18 indicates a visual impairment. The ICD-9 uses this classification to categorize visual impairments into different levels of severity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the classification of visual impairments can vary slightly between different versions of the ICD and other classification systems. However, the ICD-9 provides a widely accepted standard for reporting visual impairments.
**Correct Answer: D. Less than 6/18.**