title: Dynamic association between intraocular pressure and spontaneous pulsations of retinal veins.
abstract: OBJECTIVE
  The amplitude of spontaneous retinal venous pulsations (SRVP) is known to be affected by intraocular pressure (IOP), retinal venous pressure, and intracranial pressure (ICP). This study characterized SRVPs adjacent to the disc and quantified changes in the amplitude of these pulsations during IOP manipulation in normal subjects.
  
  
  METHODS
  The study included 12 subjects (40 ± 15, 4 females, 8 males). Baseline IOP (range 10-25 mmHg) was measured and SRVP recorded using the dynamic retinal vessel analyzer (DVA). IOP was lowered using aproclonidine 0.5% and measured every 15 min, followed by dynamic recording of SRVP. Two subjects were also tested with timolol 0.5%, and three were treated with a placebo drop. Mean amplitude of SRVP was determined within each sample at the same site. Blood pressure and heart rate were tracked continuously.
  
  
  RESULTS
  Amplitude of SRVP decreased in all subjects with reduction of IOP with aproclonidine and timolol. Mean SRVP amplitude was 8.5 ± 6 μm at baseline and reduced to 2.5 ± 1.8 μm after 45 min (p < 0.0001). IOP fell from 14.4 ± 2.6 mmHg to 10.2 ± 2.9 mmHg over the same period (p < 0.001). Venous diameter, blood pressure, and heart rate did not change significantly from the baseline. Analysis of waveforms showed a slight phase shift only (150 ± 78.5 ms, p = 0.93) between disc veins and adjacent retinal vein.
  
  
  CONCLUSIONS
  SRVPs in the peripapillary retina have similar waveform characteristics to those at the disc. SRVP amplitudes are reduced by manipulation of IOP downwards with pharmacological intervention. The relationship was consistent in all individuals tested for two classes of drugs and was independent of BP or heart rate changes.
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, 2 Technology Place, Sydney, NSW 2109, Australia. mojtaba.golzan@ieee.org
authors.forename: S Mojtaba
authors.initials: SM
authors.lastname: Golzan
authors.forename: Stuart L
authors.initials: SL
authors.lastname: Graham
authors.forename: John
authors.initials: J
authors.lastname: Leaney
authors.forename: Alberto
authors.initials: A
authors.lastname: Avolio
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D011673:Pulsatile Flow / Q000502:physiology*; D011680:Pupil / Q000187:drug effects; D012016:Reference Values; D012169:Retinal Vein / Q000502:physiology*; D014065:Tonometry, Ocular; D014331:Tropicamide / Q000008:administration & dosage
chemical_list: D014331:Tropicamide