title: The correlation between plasma osmolarity and tear osmolarity.
abstract: OBJECTIVE
  To the correlation between plasma osmolarity (Posm) and tear osmolarity (Tosm) in patients (54 patients, 88 eyes) who underwent cataract surgery was evaluated.
  
  
  METHODS
  Before cataract surgery, routine pre-operative biochemical tests were performed, and Posm was determined from blood samples. Also, Tosm was measured using the TearLab system, and objective signs including tear break-up time (BUT), fluorescein staining, lissamine green staining, and Schirmer's test were evaluated. Dry eye (DE) was diagnosed according to the Japanese criteria for DE.
  
  
  RESULTS
  Of the 88 eyes, 4 were diagnosed as definite DE, 70 as probable DE, and 14 as normal. Since the number of definite DE was small, the eyes were divided into two groups: normal group (n = 14) and DE group (n = 74), which included definite DE (n = 4) and probable DE (n = 70). There was no correlation between Posm and Tosm, though Posm (293.32 mOsm/L) was significantly higher than Tosm (288.48 mOsm/L; p < 0.001). There was no significant difference in Tosm between the normal group (288.29 mOsm/L) and the DE group (288.51 mOsm/L). No patients had a Tosm higher than 310 mOsm/L even in the DE group. Correlations between Posm/Tosm and each DE sign value were not found. Of 54 patients, 18 were diabetic. Posm was significantly higher in diabetic (295.78 mOsm/L) than in non-diabetic (292.36 mOsm/L; p = 0.014) patients, while there was no significant difference in Tosm between diabetic and non-diabetic patients.
  
  
  CONCLUSIONS
  The results suggest that Tosm is independent of Posm, and Tosm elevation in DE occurs by some local mechanisms.
authors.affiliation: Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan.
authors.forename: Maika
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan. tutomu@nms.ac.jp.
authors.forename: Tsutomu
authors.identifier: http://orcid.org/0000-0002-7467-6746
authors.initials: T
authors.lastname: Igarashi
authors.affiliation: Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan.
authors.forename: Hisatomo
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Fujimoto
authors.affiliation: Department of Ophthalmology, Musashikosugi Hospital, Nippon Medical School, 1-396 Kosugi-cho, Nakahara-ku, Kawasaki City, Kanagawa, 211-8533, Japan.
authors.forename: Hisaharu
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Ophthalmology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015352:Dry Eye Syndromes / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D010949:Plasma / Q000737:chemistry*; D013666:Tears / Q000737:chemistry*
keywords: Diabetes mellitus; Dry eye; Plasma osmolarity; Tear osmolarity