title: Prospective controlled study of vapor pressure tear osmolality and tear meniscus height in nasolacrimal duct obstruction.
abstract: OBJECTIVE
  To determine tear osmolality (TO) and tear meniscus height (TMH) in patients with functional (FNLDO) and primary acquired (PANDO) nasolacrimal duct obstruction. Additionally, to determine the effect of successful dacryocystorhinostomy surgery on these tear parameters.
  
  
  METHODS
  Prospective case-controlled interventional case series.
  
  
  METHODS
  Up to 20 microl of basal tears were collected from 20 age- and gender-matched control subjects, 33 patients with FNLDO, 28 patients with PANDO, and 31 patients after successful dacryocystorhinostomy. TMH was measured with videoreflective dacryomeniscometry, and TO was measured with vapor pressure osmometry.
  
  
  RESULTS
  Thirty-nine percent of the patients with FNLDO (13/33) elected to undergo dacryocystorhinostomy surgery, compared with 64% of the patients with PANDO (18/28; P = .09). TMH was significantly higher in the disease groups (FNLDO median, 630 +/- 187 microm; PANDO median, 620 +/- 210 microm) compared with the control subjects (median 262 +/- 50 microm; P < .01). In those patients who underwent surgery, TMH was slightly higher in FNLDO than PANDO (P = .08), and TMH reduced significantly after surgery (P < .05). Mean TO in the control subjects was 313 +/- 17 mmol/kg, in FNLDO was 309 +/- 19 mmol/kg, and in PANDO was 315 +/- 24 mmol/kg (P > .05). TO was similar in those patients who progressed to surgery compared with the total group and was unaffected by surgery.
  
  
  CONCLUSIONS
  TO was similar in normal control subjects and in the watery eye group and was unchanged after dacryocystorhinostomy surgery. Despite the slightly higher TMH in patients with FNLDO, a higher proportion of patients PANDO elected to have surgery. Relative to FNLDO, patients with PANDO who progressed to surgery had lower TMH and normal TO, which suggests that a complete lacrimal drainage obstruction induces negative feedback that results in no reduction in TO.
authors.affiliation: Vision CRC, and the School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Stahl
authors.forename: Ian C
authors.initials: IC
authors.lastname: Francis
authors.forename: Fiona
authors.initials: F
authors.lastname: Stapleton
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003608:Dacryocystorhinostomy; D005260:Female; D006801:Humans; D007767:Lacrimal Duct Obstruction / Q000150:complications*; D008297:Male; D008875:Middle Aged; D009301:Nasolacrimal Duct / Q000473:pathology*; D009994:Osmolar Concentration; D011446:Prospective Studies; D013666:Tears / Q000737:chemistry*