What will the STT results be in dogs/humans with EDED?

• A. Lower than normal
• B. Higher than normal
• C. Within normal limits
• D. Cannot be measured

Answer: (C)

STT, or Schirmer Tear Test, measures how much tear fluid the lacrimal glands produce over a minute. A result within normal limits means the aqueous tear production is adequate. Ectodermal dysplasia (EDED) can affect various structures that make up the tear film—such as goblet cells and meibomian glands—leading to a poorer tear film quality or evaporative dryness, even when the lacrimal glands are producing tears normally. So, in many dogs and humans with EDED, the tear quantity is preserved, giving a normal STT value. For reference, normal STT ranges are about 15–25 mm/min in dogs and roughly 10–25 mm/min in humans, depending on the method used. If STT were low, that would indicate reduced aqueous production, but that scenario is not typical for EDED when the question focuses on the overall pattern described.