If a secondary bacterial infection develops within the blocked duct (a condition called dacryocystitis), the fluid turns into a thick, milky white, yellow, or green discharge.

A veterinarian will perform a physical exam and may perform a . They place a harmless green dye in the eye; if the duct is open, the dye should appear at the nostril within a few minutes. If it doesn't, a blockage is confirmed.

: Antibiotic or anti-inflammatory eye drops are used if infection or swelling is the primary cause.