title: Three-dimensional volumetric assessment of the nasolacrimal duct in patients with obstruction.
abstract: OBJECTIVE
  The purpose of this study was to determine if a significant difference exists in the nasolacrimal duct volume of subjects with primary nasolacrimal duct obstruction compared with that of controls.
  
  
  METHODS
  This was a retrospective, case-control study of 70 subjects with prior maxillofacial CT scans, including 35 subjects with obstruction and 35 controls. Volume measurements of the nasolacrimal duct were made on a GE Advantage Workstation using volume viewer software, and measurements were compared using an unpaired Student t test. Interrater and intrarater reliabilities were calculated.
  
  
  RESULTS
  There was no significant difference in the nasolacrimal duct volume of patients (0.411 ± 0.18 cm) compared with that of controls (0.380 ± 0.13 cm(3)) (p = 0.23). Women had smaller volume ducts (0.356 ± 0.11 cm(3)) than that of men (0.482 ± 0.19 cm(3)) (p < 0.001). Male patients had smaller volume ducts (0.470 ± 0.23 cm(3)) than that of male controls (0.493 ± 0.14 cm(3)) (p = 0.70), while female patients (0.384 ± 0.13 cm(3)) had significantly larger volume ducts than that of female controls (0.328 ± 0.08 cm(3)) (p = 0.01). There was excellent interrater and intrarater reliabilities.
  
  
  CONCLUSIONS
  CT 3-dimensional volumetric software can be used to accurately measure the nasolacrimal duct volume in patients with obstruction. Both the absence of a significant difference in patient's and control's nasolacrimal duct volumes and the overlap in range between the 2 groups imply that the volume of the tear duct is likely not related to the etiology of obstruction. The increase in volume seen in females with obstruction may be due to expansion of the bony canal during the postmenopausal years. The exact etiology of primary nasolacrimal duct obstruction requires further investigation.
authors.affiliation: *Weill Cornell Medical College and †Department of Radiology, Weill Cornell Medical College, Cornell University; ‡NewYork-Presbyterian Hospital; §Department of Public Health and ‖Department of Ophthalmology, Weill Cornell Medical College, Cornell University, New York, New York, U.S.A.
authors.forename: Jaclyn L
authors.initials: JL
authors.lastname: Estes
authors.forename: Apostolos J
authors.initials: AJ
authors.lastname: Tsiouris
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Christos
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Lelli
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007767:Lacrimal Duct Obstruction / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009301:Nasolacrimal Duct / Q000000981:diagnostic imaging*; D015588:Observer Variation; D012189:Retrospective Studies