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Related Experiment Videos

What does the phenol red thread test actually measure?

A Tomlinson1, K J Blades, E I Pearce

  • 1Department of Vision Sciences, Glasgow Caledonian University, United Kingdom. A.Tomlinson@gcal.ac.uk

Optometry and Vision Science : Official Publication of the American Academy of Optometry
|May 1, 2001
PubMed
Summary
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The phenol red thread test (PRT) does not accurately measure tear volume or production. This study found no correlation between PRT results and other established tear measurement techniques.

Area of Science:

  • Ophthalmology
  • Biomedical Engineering

Background:

  • The phenol red thread test (PRT) is a common method for assessing tear film characteristics.
  • Its ability to accurately quantify tear volume or production remains debated.

Purpose of the Study:

  • To determine if the phenol red thread test (PRT) measures tear volume or tear production.
  • To compare PRT results with established tear assessment techniques.

Main Methods:

  • Twenty asymptomatic subjects underwent the PRT (Zone Quick, Menicon).
  • PRT results were compared with tear turnover rate measured by fluorophotometry and tear volumes derived from tear meniscus height and fluorometric data.

Main Results:

  • No statistically significant correlation was found between PRT wetting and tear turnover rate (p > 0.05).

Related Experiment Videos

  • PRT wetting also showed no correlation with tear volumes measured by fluorophotometry or tear meniscus height (p > 0.05).

    • Conclusions:

    • The study found no clear experimental evidence supporting the PRT as a measure of tear production or volume.
    • It is suggested that the PRT may reflect fluid uptake, minor reflex tearing, and thread absorption properties rather than true tear volume or production.