Ophthalmology: Phenol Red Thread Test
The methods for the Phenol Red Thread Test are based on a clinical exam called the Color Bar Schirmer Tear Test that is used in the diagnosis and treatment of dry eye in humans. The mice are gently restrained (not anesthetized) and a phenol red loaded thread (Zone-Quick) is placed in the lateral canthus for 20 seconds to measure tear production. The amount of thread that turns red (change in pH from wetting by tears) is measured in millimeters. The procedure is then repeated on the left eye and the average of the 2 measures is obtained for each mouse.
Displayed below is a sample graph of how phenol red thread test results are presented. In comprehensive phenotypic data packages graphs are interactive. Raw or calculated data and statistics can be seen by clicking on points in the graph.