title: Episcleral venous pressure in younger and older subjects in the sitting and supine positions.
abstract: OBJECTIVE
  Intraocular pressure is higher in older than younger subjects during the day and night. We attempted to determine whether episcleral venous pressure could explain the difference in the sitting and supine positions.
  
  
  METHODS
  We compared episcleral venous pressure, intraocular pressure, and blood pressure in a group of younger subjects aged 18 to 30 years and in a group of older subjects aged 65 years or older. The above measurements were performed in the sitting position and after 15 minutes in the supine position.
  
  
  RESULTS
  The main difference between the groups was their systemic conditions. Comparing both groups, episcleral venous pressure and intraocular pressure were not different in the sitting position. However, in the supine position, episcleral venous pressure (9.6 vs. 8.3 mm Hg) (P < 0.01) and intraocular pressure (17.1 vs. 15.6 mm Hg) (P < 0.05) were higher in the older group. Statistically, a within-group analysis showed a significant increase in intraocular pressure in the supine position for both the younger (+ 0.8 mm Hg) (P < 0.001) and older subjects (+ 1.8 mm Hg) (P < 0.02). This was associated with an increased episcleral venous pressure in younger (+ 0.4 mm Hg) (P < 0.001) and older subjects (+1 mm Hg) (P < 0.02). There was no gender difference in intraocular pressure and episcleral venous pressure. No differences were found for intraocular pressure and episcleral venous pressure in subjects having certain systemic conditions. Blood pressure was higher for older subjects (P < 0.001). It decreased in the supine position for both groups (P < 0.001).
  
  
  CONCLUSIONS
  Intraocular pressure and episcleral venous pressure were not different in the younger and older group in the sitting position. They were higher in the supine position for older subjects. There was no gender difference.
authors.affiliation: Department of Surgery, University of Sherbrooke, Quebec, Canada.
authors.forename: Mazen
authors.initials: M
authors.lastname: Sultan
authors.forename: Pierre
authors.initials: P
authors.lastname: Blondeau
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001794:Blood Pressure; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D011187:Posture / Q000502:physiology*; D012590:Sclera / Q000098:blood supply*; D016683:Supine Position / Q000502:physiology; D014690:Venous Pressure