ExoticRx · exoticrx.com/drugs/phenol-red-thread-test
US brand names:Zone-Quick
pH-sensitive dye thread placed in lower conjunctival fornix. Tears change thread color from yellow to red, measuring tear production in 15 seconds.
Less invasive than Schirmer tear test. Good for exotic species and cats. Normal values differ by species. Not a therapeutic agent.
Species references:All Cat (Domestic) drugsAll Dog (Domestic) drugs
Each ExoticRx dose rule is graded by the strength of its primary evidence — see the editorial process.
A dog/cat sample is shown here. Cited dosing for all 2 species — reptiles, birds, pocket pets, livestock, and equine — is free on the per-species pages above. Pro adds the weight-based calculator for every species.
| Species | Route | Dose | Frequency | Evidence | Source |
|---|---|---|---|---|---|
| Cat (Domestic) | TOPICAL (ophthalmic) | Normal cat: >15mm wetting | PRN (diagnostic) | Moderate | Brown, M.H., Brightman, A., Butine, M., & Moore, T. (1997) The phenol red thread tear test in healthy cats. Veterinary & Comparative Ophthalmology, 7, 249-252. — Verified against Veterinary Ophthalmology (Gelatt), 6th Ed, p.628 (2026-08-01). |
| Dog (Domestic) | TOPICAL (ophthalmic) | Place folded end in lower conjunctival fornix for 15 seconds | PRN (diagnostic) | Moderate | Brown, M.H., Galland, J.C., Davidson, H.J., & Brightman, A.H. (1996) The phenol red threat tear test in dogs. Veterinary & Comparative Ophthalmology, 6, 274-277. — Verified against Veterinary Ophthalmology (Gelatt), 6th Ed, p.628 (2026-08-01). |
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