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

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.