What is visual impairment?

According to the International Classification of Diseases 11th Revision published by World Health Organization, visual impairment is categorized into four groups based on an individual's better eye visual acuity:

• Blind – visual acuity worse than 3/60

• Severe – visual acuity better than 3/60, but worse than 6/60

• Moderate – visual acuity better than 6/60, but worse than 6/18

• Mild – visual acuity better than 6/18, but worse than 6/12