Vitamin A deficiency causes corneal xerosis and keratomalacia. The WHO grading of xerophthalmia that indicates irreversible corneal damage and imminent blindness is:

• A XN — night blindness
• B X1B — conjunctival xerosis (Bitot's spots)
• C X3B — keratomalacia affecting ≥1/3 of the cornea ✓
• D X2 — corneal xerosis

Explanation

The WHO grading of xerophthalmia classifies: XN (night blindness), X1A (conjunctival xerosis), X1B (Bitot's spots), X2 (corneal xerosis), X3A (corneal ulceration/keratomalacia <1/3 cornea), X3B (keratomalacia ≥1/3 cornea), XS (corneal scar), XF (xerophthalmic fundus). X3B — keratomalacia affecting one-third or more of the corneal surface — represents irreversible melting of the cornea leading to permanent blindness (phthisis bulbi). X3A and beyond indicate corneal involvement; X3B is the threshold for likely blindness. Stages XN to X2 are largely reversible with vitamin A supplementation.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.