What is the gold standard diagnostic test for Aqueous dry eye disease (ADDE)?

• A. Schirmer Tear Test (STT)
• B. Interferometry
• C. Tear osmolarity
• D. TBUT

Answer: (A)

In aqueous deficient dry eye, the central problem is reduced tear production from the lacrimal glands. The Schirmer tear test directly measures how much tear fluid is being produced over a short period, making it the best way to quantify aqueous tear production. A small filter paper strip is placed in the lower eyelid, and after about a minute the extent to which the strip wets reflects the volume of tear produced. Because this test specifically assesses lacrimal tear production, it accurately identifies aqueous deficiency.

Other tests assess different aspects of the tear film. Interferometry looks at the lipid layer, TBUT evaluates how long the tear film remains stable before breaking up, and tear osmolarity reflects the overall balance and inflammation of the tear film. While helpful for characterizing dry eye, none of these directly quantify tear production the way the Schirmer test does, which is why it remains the standard for diagnosing ADDE.

In clinical use, remember that normal values can vary by species and technique (with or without anesthesia affecting what is measured), so a result indicating markedly reduced tear production in the appropriate clinical context supports aqueous deficiency.