The dynamics of tear flow within a phenol red impregnated thread

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Physiology

Background:

• Accurate measurement of tear flow is crucial for diagnosing and managing dry eye disease.
• Existing methods for tear flow assessment have limitations in precision and ease of use.
• Phenol red impregnated threads offer a standardized approach to quantify tear fluid dynamics.

Purpose of the Study:

• To describe a laboratory method for producing phenol red impregnated threads for tear flow measurement.
• To evaluate tear flow rates in different age groups using the phenol red thread test.
• To determine the relationship between thread insertion time and tear wetting rate.

Main Methods:

• Phenol red impregnated threads were used to measure tear flow in two age groups (younger and older adults).
• Threads were placed on the lower eyelid margin for varying durations (15s to 120s).
• Tear wetting of the threads was quantified, and data were analyzed for age and gender dependency.

Main Results:

• Significant differences in mean thread wetting were observed between age groups at insertion times of 30, 60, and 90 seconds.
• The rate of thread wetting demonstrated an exponential relationship with the period of thread insertion.
• Tear wetting was not found to be dependent on gender, and the exponential constant was attributed to thread material properties.

Conclusions:

• The phenol red thread test provides a reliable method for assessing tear flow, with notable age-related variations.
• Tear flow dynamics can be accurately modeled using an exponential function of insertion time.
• The developed method offers a practical approach to tear flow assessment, reaching equilibrium by 120 seconds.