Certified Paraoptometric (CPO) Practice Exam 2025

What is the primary function of the nasolacrimal duct?

1. The storage of tears

2. The drainage system for tears to exit the eye

3. The production of tears

4. The protection of the eye from foreign objects

The correct answer is: The drainage system for tears to exit the eye

The primary function of the nasolacrimal duct is to serve as the drainage system for tears, allowing them to exit the eye. Tears are produced by the lacrimal glands and spread across the surface of the eye during blinking to keep it moist and free from debris. After their role in lubrication, tears need to be drained away, preventing overflow and maintaining proper ocular health. The nasolacrimal duct transports the tears from the lacrimal sac into the nasal cavity, which is why we may notice a runny nose when we cry. This function is crucial for maintaining the delicate balance of tear film on the eye's surface, which aids in clear vision and protects the cornea. While tears are indeed stored in the lacrimal sac before they enter the nasolacrimal duct, that storage is not the duct's primary function; it is focused on drainage. Tear production occurs in the lacrimal glands, and the eye's protection from foreign objects is managed by the eyelids and eyelashes. Thus, the drainage of tears is the key role that the nasolacrimal duct fulfills.