title: The phenol red thread tear test: a cross-cultural study.
abstract: OBJECTIVE
  To examine the results of the phenol red thread tear test in a cross-cultural comparison.
  
  
  METHODS
  Two groups of 500 controlled normal subjects who do not wear contact lenses from the United States and Japan were investigated.
  
  
  RESULTS
  The mean wet length of the thread for the United States was 23.9 mm (SD 9.5 mm). The mean for Japan was 18.8 mm (SD 8.6 mm). There was a significant difference between the two countries (P < 0.05). Males subjects had significantly longer wet lengths than females for both countries (P < 0.05). There was a moderate correlation between right and left eye results for both countries.
  
  
  CONCLUSIONS
  The phenol red thread tear test was found to be easy to administer. Results were in line with current knowledge and theories of the lacrimal system. Results also indicated that this test may disclose subtle differences not previously found with other tear tests.
authors.affiliation: Department of Ophthalmology, Tokyo Women's Medical College, Daini Hospital, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Sakamoto
authors.forename: E S
authors.initials: ES
authors.lastname: Bennett
authors.forename: V A
authors.initials: VA
authors.lastname: Henry
authors.forename: S
authors.initials: S
authors.lastname: Paragina
authors.forename: T
authors.initials: T
authors.lastname: Narumi
authors.forename: Y
authors.initials: Y
authors.lastname: Izumi
authors.forename: Y
authors.initials: Y
authors.lastname: Kamei
authors.forename: E
authors.initials: E
authors.lastname: Nagatomi
authors.forename: Y
authors.initials: Y
authors.lastname: Miyanaga
authors.forename: H
authors.initials: H
authors.lastname: Hamano
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003431:Cross-Cultural Comparison; D015352:Dry Eye Syndromes / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan; D007765:Lacrimal Apparatus / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010637:Phenolsulfonphthalein; D012016:Reference Values; D012737:Sex Factors; D013666:Tears / Q000378:metabolism*; D014481:United States
chemical_list: D010637:Phenolsulfonphthalein