Comparison of thread test of lacrimation to Schirmer test

A modified Schirmer test using thread instead of filter paper has been previously reported. The present report compares the characteristics of thread and filter paper and establishes the normal range for the tear flow rate. The moisture absorption by a 5-mm wide strip of filter paper was 0.765 microL/mm and that by a thread was 0.054 microL/mm. The thread was 14 times more sensitive in detecting small amounts of fluid than was the filter paper. The thread test was used in 42 normal subjects. The normal range was 60% to 140% (+/- 3 SD), so a value of less than 60% was considered to indicate lacrimal hypofunction, and over 140%, hyperfunction.