title: Lacrimal sac volume measurement during eyelid closure and opening.
abstract: BACKGROUND
  Jones' theory of tear drainage suggests that the lacrimal sac fills when the eyelids are closed and empties when the eyelids are opened. This study was undertaken to see if there is any change in the volume of the lacrimal sac during eyelid closure and opening using images obtained from magnetic resonance dacryocystography using a topical magnetic resonance contrast agent.
  
  
  METHODS
  This is a prospective non-randomized comparative study in a tertiary hospital setting. Magnetic resonance dacryocystography scans were performed on five volunteers using 0.5% topical gadolinium-DTPA (MagneVist, Schering AG, Berlin, Germany) as a contrast agent. A T1-weighted magnetic resonance imaging scan with 2-mm contiguous coronal cuts was performed after localizing the lacrimal sac and instilling the contrast agent. The scans were performed with eyelids closed and opened. Volumes of 10 lacrimal sacs of five volunteers were calculated using pixel calibration and computer graphics.
  
  
  RESULTS
  No statistical difference in size of the lacrimal sacs was demonstrable between when the eyes were opened and when they were shut.
  
  
  CONCLUSIONS
  The present study could not demonstrate any volume change in the sac between eyelid closure and opening. Magnetic resonance imaging dacryocystography measures sac volume at two static end-points, so it cannot show any transient volume change that might occur during blinking. Various factors that may be affecting tear flow through the nasolacrimal system are discussed.
authors.affiliation: Department of Ophthalmology, National University Hospital, Singapore. ophv14@nus.edu.sg
authors.forename: Shantha
authors.initials: S
authors.lastname: Amrith
authors.forename: Poh Sun
authors.initials: PS
authors.lastname: Goh
authors.forename: Shih-Chang
authors.initials: SC
authors.lastname: Wang
mesh_terms: D001767:Blinking / Q000502:physiology*; D001837:Body Weights and Measures; D003287:Contrast Media; D005143:Eyelids / Q000502:physiology*; D019786:Gadolinium DTPA; D006801:Humans; D007765:Lacrimal Apparatus / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011446:Prospective Studies; D013666:Tears / Q000378:metabolism
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA