The nasolacrimal duct is not fully patent until what age?

• A. Two to three months of age
• B. Three to five months of age
• C. Five to seven months of age
• D. Seven to nine months of age

Answer: (C)

Patency of the nasolacrimal duct develops as the canalization of the duct finishes after birth. Right after birth, the distal Hasner valve is often not fully open, causing transient obstruction that leads to tearing and discharge in infancy. As canalization progresses, most infants have a fully patent duct by about five to seven months of age. This timing explains why congenital nasolacrimal duct obstruction often improves spontaneously within the first several months. If obstruction persists beyond that window, further evaluation may be needed.