According to WHO criteria for blindness (used in NPCB), a person is classified as blind if their presenting visual acuity in the better eye is:

• A Less than 6/60 (20/200) or visual field less than 20 degrees
• B Less than 6/18 in both eyes
• C Less than 6/6 corrected with spectacles
• D Less than 3/60 (20/400) or visual field less than 10 degrees in the better eye with best correction ✓

Explanation

The WHO 2003 classification (ICD-10 update) defines blindness as presenting visual acuity worse than 3/60 (20/400, or 1/20) or visual field less than 10 degrees in the better eye. This replaced the older threshold of <3/60. For programmatic purposes in India, the NPCB uses <6/60 visual acuity in the better eye after best correction as the functional definition of blindness for programme enumeration, while economic blindness is defined as <3/60. Candidates should know both definitions.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.