Schirmer I test
We introduced the Schirmer I test to measure lacrimal flow (LF) without previous topical anesthetic to measure the tear secretion. A Whatman special filter paper strip of 20 mm*5 mm (Cytiva®, Shanghai, China) were placed in the lateral 1/3 of the lower bilateral eyelid. The length of the moistened portion of the strip was measured at the fifth minute