UPSC-CMS 2010 — Ophthalmology

Q: Consider the following : 1. Night blindness 2. Corneal xerosis 3. Conjunctival xerosis 4. Keratomalacia What is the correct sequence of the above in the progress of clinical presentation of vitamin A deficiency blindness?

1-3-2-4. ***1-3-2-4*** - This is the **correct sequence** according to WHO classification of xerophthalmia in vitamin A deficiency. - **Night blindness (XN)** is typically the **earliest clinical manifestation**, resulting from impaired rod photoreceptor function due to insufficient rhodopsin synthesis. - This is followed by **conjunctival xerosis (X1A)**, characterized by dryness and thickening of the bulbar conjunctiva, often accompanied by Bitot's spots (X1B) - foamy triangular patches of keratinized epithelium. - As deficiency progresses, **corneal xerosis (X2)** develops, with dryness extending to the corneal surface, creating a hazy, lusterless appearance. - The final and most severe stage is **keratomalacia (X3)**, involving corneal softening, ulceration, and potential perforation leading to irreversible blindness. *2-1-4-3* - This sequence incorrectly places **corneal xerosis** before **night blindness**. - Night blindness is a functional symptom that appears early, while corneal xerosis is a later structural change. - The progression also illogically places keratomalacia before conjunctival xerosis. *1-2-3-4* - This sequence incorrectly suggests **corneal xerosis** precedes **conjunctival xerosis**. - In vitamin A deficiency, xerosis (dryness) affects the **conjunctiva first**, then progresses to involve the **cornea**. - The conjunctiva is more susceptible to early changes than the cornea. *1-3-4-2* - This sequence incorrectly places **keratomalacia** before **corneal xerosis**. - Keratomalacia represents corneal softening and melting, which cannot occur before the cornea becomes xerotic (dry). - Corneal xerosis is a **prerequisite** for the development of keratomalacia. [Practice more Ophthalmology PYQs on OnCourse]

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Consider the following : 1. Night blindness 2. Corneal xerosis 3. Conjunctival xerosis 4. Keratomalacia What is the correct sequence of the above in the progress of clinical presentation of vitamin A deficiency blindness?