title: Pulsatile ocular blood flow: the effect of the Valsalva manoeuvre in open angle and normal tension glaucoma: a case report and prospective study.
abstract: OBJECTIVE
  A case of severe normal tension glaucoma is reported in a trumpet player, along with a study investigating the association between glaucoma and raised intrathoracic pressure, using measurements of pulsatile ocular blood flow (POBF).
  
  
  METHODS
  Three patient groups were studied; normals (n = 34), untreated primary open angle glaucoma (POAG) (n = 20), and untreated normal tension glaucoma (NTG) (n = 22), with a total of 76 patients who underwent measurements of POBF using the OBF pneumotonometer at rest and while forcibly exhaling through a mouthpiece connected to a mercury manometer (30 mm Hg) (Valsalva manoeuvre).
  
  
  RESULTS
  POBF fell during Valsalva in all groups with the greatest predictor being the resting value of POBF. There was no evidence of significant differences in the mean change in POBF occurring during the Valsalva manoeuvre for the three groups studied before or after adjusting for the sex, the resting POBF, and the resting IOP of the patients (p = 0.294 and p = 0.542, respectively). However, statistically significant associations were found between the change in POBF and sex (p = 0.049), resting POBF (p<0.0001) and resting IOP (p = 0.032). Males had a greater drop, on average, in POBF during Valsalva manoeuvre than females after adjusting for the other factors. Additionally, there was a significant difference in the mean change in IOP during Valsalva for the three groups (p = 0.002), with the difference occurring between the normal and POAG groups (p<0.005). The POAG group had, on average, a drop in IOP during Valsalva, while the other two groups had an increase in IOP. Also noted was a significant difference in the distributions of the risk factors among the three groups (p = 0.002).
  
  
  CONCLUSIONS
  This study demonstrates no difference between groups with respect to resting or Valsalva POBF, but does demonstrate a possible trend with respect to IOP, with a drop in IOP occurring during Valsalva in the POAG group. There is, however, much variability in the data left unexplained by our models. Thus, unfortunately, we cannot advise our trumpet player whether his NTG is directly related to his trumpet playing.
authors.affiliation: AMD Study, Box 261, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Khan
authors.forename: E H
authors.initials: EH
authors.lastname: Hughes
authors.forename: B D
authors.initials: BD
authors.lastname: Tom
authors.forename: J P
authors.initials: JP
authors.lastname: Diamond
mesh_terms: D000367:Age Factors; D000368:Aged; D005123:Eye / Q000098:blood supply*; D005260:Female; D005901:Glaucoma / Q000209:etiology / Q000503:physiopathology*; D005902:Glaucoma, Open-Angle / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D011673:Pulsatile Flow; D012030:Refractive Errors / Q000150:complications; D012044:Regression Analysis; D012737:Sex Factors; D014636:Valsalva Maneuver