What is the significance of measuring tear volume?

Measuring tear volume helps assess the severity of dry eye disease and the effectiveness of treatments.

How does the phenol red thread work?

The phenol red thread changes color when it contacts the alkaline tear film, allowing for measurement of tear volume.

What are the implications of reduced tear volume?

Reduced tear volume can lead to discomfort, inflammation, and damage to the ocular surface.

Can this method be applied to other animal models?

Yes, the phenol red thread method can be adapted for use in various animal models to study tear production.

What future research could stem from this study?

Future research may focus on developing treatments for dry eye disease based on tear volume measurements.

Is this method suitable for clinical use?

While primarily used in research, the method has potential for clinical applications in assessing dry eye disease.

Quantification of Tear Volume in an Autoimmune Dry Eye Rat Model using the Phenol Red Thread

JoVE Encyclopedia of Experiments

Immunology

0 views • 1:46 min • July 8th, 2025

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In certain autoimmune diseases, the immune system attacks the lacrimal and meibomian glands and the ocular surface, resulting in impaired tear stability and production, leading to dry eye disease.

To quantify the tear volume, begin with an anesthetized autoimmune disease rat model.

Take a phenol red thread, a cotton thread impregnated with phenol red, a pH-sensitive dye.

Pull the rat's lower eyelid to place the phenol red thread at the proximal corner of the lower fornix for maximum contact with the tear film.

Allow time for the tear film to moisten the phenol red thread.

As the phenol red thread contacts the alkaline tear film, it changes from yellow to red.

Now, measure the wetted length of the thread that appears red, indicating the tear volume.

A shorter wetted length of the phenol red thread in the autoimmune disease rat model than in the control rat model indicates less tear volume.

While holding an anesthetized rat according to the text protocol, to measure the tear volume with phenol red thread, use one pair of forceps to hold the thread and another to pull the lower eyelid of the rat. Place the thread at the proximal corner of the lower fornix for one minute, and then, remove the thread. Then, place the thread next to a ruler with millimeter markings, and take an image of the length of the wetted part of the thread.