Basal precorneal tear turnover in the human eye

Area of Science:

• Ophthalmology
• Tear Film Dynamics
• Corneal Physiology

Background:

• The precorneal tear film is crucial for maintaining ocular surface health and visual acuity.
• Understanding tear film turnover is essential for diagnosing and managing dry eye disease and other ocular surface disorders.

Purpose of the Study:

• To establish a simple method for measuring the rate of fluorescein dye loss from the precorneal tear film.
• To determine the normal range of the tear elimination coefficient in healthy subjects.
• To investigate potential correlations between tear elimination and demographic factors.

Main Methods:

• A simple method was employed to measure fluorescein dye loss from the central precorneal tear film in 51 normal subjects.
• 1 microliter of a 10% sodium fluorescein solution was applied to the lower cul-de-sac.
• Dye concentration was monitored over time to determine the tear elimination coefficient.

Main Results:

• In 29% of subjects, no measurable dye remained after 30 minutes.
• 61% of subjects exhibited an exponential dye decay between 15 and 30 minutes.
• The mean tear elimination coefficient was 15%/min, with 95% confidence limits estimated at 5-30%/min.
• No significant correlations were found between tear elimination coefficient and sex, eye color, or contact lens use.

Conclusions:

• The developed method provides a reliable measure of tear film clearance.
• The study establishes normative values for the tear elimination coefficient in a healthy population.
• Tear film clearance, as measured by this method, is not significantly influenced by sex, eye color, or contact lens wear.