What does a normal STT indicate about tear production?

• A. Normal aqueous tear production
• B. Reduced tear production
• C. Excessive tear production
• D. Unreliable tear production

Answer: (A)

Schirmer tear test measures how much aqueous tear fluid is produced over a fixed period. A normal result means there is adequate aqueous tear production. In most dogs and cats, a normal STT value is around 15 mm/min or higher (often cited roughly 15–25 mm/min). If the STT is normal, the aqueous component of the tear film is sufficient, so dry eye due to tear production deficiency is unlikely. Remember, this test only assesses the aqueous portion of tears and does not evaluate tear film quality, mucin, lipid layers, or tear evaporation, so other factors can still contribute to ocular surface dryness or irritation even with a normal STT.