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.

Figure represents average thread wetting per 20 seconds of male and female (left), male (center), and female (right) mutant mice. Thread wetting values of wild type littermates (green circle), homozygous (red diamond), and recent historical wild type (purple line) mice are plotted against long-term historical values (+/- 2 standard deviations) for wild type animals (green shading). Recent wild type values are calculated from data collected within 60 days of current measures and long-term historical values are derived from data collected on more than 10,000 wild type mice.