IN THE course of a clinical study of keratoconjunctivitis sicca, the question arose as to what constitutes a normal flow of tears. In the search of the literature we found that several authors1 had postulated certain values as comprising the normal flow of tears during their clinical observations on eyes with keratoconjunctivitis sicca. Schirmer,2 who originated the test on which most clinical observations are now based, investigated the flow of tears in 100 eyes which he considered normal. He came to the conclusion that a normal person secretes from 0.5 to 0.67 Gm. of tears per day and that more than 15 mm. of wetting in five minutes was normal when his filter paper method 1 was used to determine the flow. Schirmer, however, did not tabulate the results in all of the cases, so that the reader does not know the exact range of values that constituted
HENDERSON JW, PROUGH WA. INFLUENCE OF AGE AND SEX ON FLOW OF TEARS. Arch Ophthalmol. 1950;43(2):224–231. doi:10.1001/archopht.1950.00910010231004
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