title: Effect of Head Position and Weight Loss on Intraocular Pressure in Obese Subjects.
abstract: OBJECTIVE
  To measure the influence of body weight on postural intraocular pressure (IOP) changes and to determine if significant weight loss effects IOP.
  
  
  METHODS
  In this prospective case-control study 25 morbidly obese subjects scheduled for bariatric surgery and 25 age-matched and sex-matched normal weight controls were recruited. Subjects had tonometry performed in 7 positions with the order randomized: sitting with the neck in neutral position, neck flexion at 30 degrees, extension at 30 degrees, supine, right, and left lateral decubitus, and with the head and upper body elevated at 30 degrees. The obese subjects were reassessed 1 to 2 years after bariatric surgery.
  
  
  RESULTS
  Mean IOP in the obese group was significantly higher than the control group across all positions by a mean of 2.5±0.4 mm Hg (P<0.02). There was no significant difference in the magnitude of postural IOP change between obese and control subjects. In total, 19 obese subjects completed follow-up after bariatric surgery. Mean weight loss was 49.1±17.2 kg, 36% of total body weight. Mean IOP was significantly lower after bariatric surgery by 1.6±0.5 mm Hg (P<0.001). Linear regression demonstrated that every 10% body weight loss was correlated with 1.4 mm Hg decrease in IOP (r=-0.46).
  
  
  CONCLUSIONS
  Obesity is associated with increased IOP compared with normal weight controls, but not with the magnitude of postural IOP change across different seated and supine positions. Significant weight loss after bariatric surgery is weakly associated with IOP lowering. The relationship between IOP, glaucoma, and obesity deserves further study.
authors.affiliation: Department of Ophthalmology & Vision Sciences, University of Toronto, Toronto, ON, Canada.
authors.forename: Cindy T Y
authors.initials: CT
authors.lastname: Lam
authors.forename: Graham E
authors.initials: GE
authors.lastname: Trope
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Buys
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D001835:Body Weight / Q000502:physiology; D016022:Case-Control Studies; D005260:Female; D006257:Head / Q000502:physiology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D014065:Tonometry, Ocular; D015431:Weight Loss / Q000502:physiology*