title: Head-down posture induces PERG alterations in early glaucoma.
abstract: OBJECTIVE
  To probe susceptibility of retinal ganglion cells (RGC) to physiological stressors associated with moderate head-down body tilt in patients with suspicion of glaucoma or early manifest glaucoma (EMG).
  
  
  METHODS
  One hundred nine subjects with best corrected visual acuity (BCVA) ≥ 20/20 and no disease other than glaucoma [glaucoma suspects (GS)=79, EMG=14, normal controls (NC)=16 and comparable age range were tested. Noncontact intraocular pressure (IOP), pattern electroretinogram (PERG), and brachial blood pressure/heart rate measurements were performed in 3 consecutive conditions (∼0038 min apart): seated (baseline), -10-degree whole body head-down tilt (HDT), and seated again (recovery). PERG amplitude and latency, IOP, and systolic/diastolic blood pressures, heart rate, calculated mean central retinal artery pressure, ocular perfusion pressure, and systolic/diastolic perfusion pressures were evaluated.
  
  
  RESULTS
  During HDT, IOP significantly (P<0.001) increased in all groups approximately to the same extent (approximately 20%). PERG amplitude did not change in NC but decreased significantly (P<0.001) in patients (GS, -25%, EMG -23%). PERG phase become delayed in NC (-1.6%, P=0.04) but more so in patients (GS, -2.7%, P<0.001; EMG, -6.0%, P<0.001). The proportion of patients with PERG alterations significantly (P<0.05) exceeding those occurring in age-adjusted and baseline-adjusted NC were, GS: amplitude 20%, phase 15%; EMG: amplitude 14%, phase 50%. All measures recovered baseline values after HDT.
  
  
  CONCLUSIONS
  Moderate HDT induces temporary worsening of RGC function in a subpopulation of GS and EMG patients. This noninvasive protocol may help disclose abnormal susceptibility of RGCs in a subset of the patients at risk of glaucoma.
authors.affiliation: Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Lori M
authors.initials: LM
authors.lastname: Ventura
authors.forename: Iuri
authors.initials: I
authors.lastname: Golubev
authors.forename: William
authors.initials: W
authors.lastname: Lee
authors.forename: Izuru
authors.initials: I
authors.lastname: Nose
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Parel
authors.forename: William J
authors.initials: WJ
authors.lastname: Feuer
authors.forename: Vittorio
authors.initials: V
authors.lastname: Porciatti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology; D004596:Electroretinography; D018475:Head-Down Tilt / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D012164:Retinal Diseases / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology