In congenital nasolacrimal duct obstruction (CNLDO), the site of membranous obstruction that fails to canalise at birth is:
- A Valve of Hasner (plica lacrimalis) at the junction of the nasolacrimal duct and inferior meatus ✓
- B Valve of Rosenmüller at the common canalicular opening
- C Lacrimal sac at its junction with the canaliculi
- D Valve of Krause in the upper nasolacrimal duct
Correct answer: A. Valve of Hasner (plica lacrimalis) at the junction of the nasolacrimal duct and inferior meatus
Explanation
CNLDO results from failure of canalisation of the distal nasolacrimal duct at the valve of Hasner, which is a membranous fold at the lower end of the nasolacrimal duct as it enters the inferior meatus of the nasal cavity. This persists in approximately 6% of term neonates and resolves spontaneously in >90% by 12 months. Rosenmüller's valve is at the common internal punctum; it prevents retrograde reflux. Persistent obstruction beyond 12–13 months is an indication for nasolacrimal duct probing.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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