In congenital nasolacrimal duct obstruction (CNLDO), the most common site of obstruction and the correct timing for probing if conservative treatment fails are:

• A Obstruction at the canaliculus; probe at 6 weeks of age
• B Obstruction at the common canaliculus; immediate dacryocystorhinostomy at 3 months
• C Obstruction at the distal end (valve of Hasner); probe after 12–18 months if conservative treatment (massage + topical antibiotics) fails ✓
• D Obstruction at the valve of Rosenmuller; probing at 6 months is mandatory regardless of massage

Explanation

In CNLDO, the obstruction is most commonly at the valve of Hasner (at the distal end of the nasolacrimal duct where it opens into the inferior meatus of the nose) due to failure of canalization of a membranous remnant. Spontaneous resolution occurs in up to 90% of cases by 12 months with Crigler massage (pressure over lacrimal sac) and topical antibiotics for secondary infection. Probing is recommended after 12–18 months if conservative treatment fails. Before 12 months, most cases resolve spontaneously and probing carries a small but real risk under general anaesthesia.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.