title: Diurnal variation of episcleral venous pressure in healthy patients: a pilot study.
abstract: OBJECTIVE
  To study diurnal episcleral venous pressure (EVP) and its relation to intraocular pressure (IOP) in healthy patients. The influences of supine position and lid closure on EVP were also studied.
  
  
  METHODS
  Experimental observational study.
  
  
  METHODS
  Twelve healthy patients with no eye disease had their IOP and EVP measured at 16h00, 22h00, 22h30, 06h00, 06h30, 09h00, 12h00, and 16h00. Measurements at 22h30, 06h00, and 06h30 were performed on supine patients, and the measurement at 06h00 was with the eye that had been closed for the whole night. In a second experiment, EVP was measured on patients who were lying supine from 22h30 to 16h00 with one eye closed during the day.
  
  
  METHODS
  Episcleral venous pressure and IOP at varying time points during a 24-hour period.
  
  
  RESULTS
  Episcleral venous pressure was relatively constant throughout the day except for a slight reduction at 22h00. After lying down, the EVP increased by 3.6 mm Hg and remained increased as long as the patient remained in this position. Eyelid closure did not affect EVP. IOP measured with the Tono-Pen closely followed the variations in EVP.
  
  
  CONCLUSIONS
  Episcleral venous pressure remains relatively constant throughout the day. It increases in the supine position with a corresponding increase in IOP. Lid closure does not influence EVP or IOP.
authors.affiliation: University of Sherbrooke, Quebec, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Blondeau
authors.forename: J P
authors.initials: JP
authors.lastname: Tétrault
authors.forename: C
authors.initials: C
authors.lastname: Papamarkakis
mesh_terms: D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012590:Sclera / Q000098:blood supply*; D016683:Supine Position; D014065:Tonometry, Ocular; D014690:Venous Pressure / Q000502:physiology*