title: The response of retrobulbar vasculature to hypercapnia in primary open-angle glaucoma and ocular hypertension.
abstract: OBJECTIVE
  To evaluate the physiological effects of hypercapnia on the retrobulbar vasculature in ocular hypertension (OH) and open-angle glaucoma (OAG).
  
  
  METHODS
  Peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI) of the ophthalmic (OA) and central retinal arteries (CRA) were evaluated in 12 eyes with OH and 8 eyes with OAG using color Doppler imaging. Measurements were taken before and during hypercapnia.
  
  
  RESULTS
  Patients with OAG were found to have increased EDV (p < 0.035) of the CRA, and decreased PSV (p < 0.097) and EDV (p < 0.098) of the OA, during hypercapnia. Patients with OH had increased PSV (p < 0.062) and EDV (p < 0.072) of the CRA during hypercapnia. Patients with OH also demonstrated a greater percent change in the calculated RI (p < 0.065) of the CRA in response to hypercapnia when compared to OAG. The mean RI of the CRA decreased during hypercapnia.
  
  
  CONCLUSIONS
  Patients with OH were found to have a normal vasodilatory response within the retrobulbar vasculature during hypercapnia resulting in increased volumetric blood flow to the retina while patients with OAG did not, suggesting there is vasospasm at or downstream from the CRA resulting in decreased volumetric blood flow to the retina.
authors.affiliation: Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: D
authors.initials: D
authors.lastname: Sines
authors.forename: A
authors.initials: A
authors.lastname: Harris
authors.forename: B
authors.initials: B
authors.lastname: Siesky
authors.forename: I
authors.initials: I
authors.lastname: Januleviciene
authors.forename: C L
authors.initials: CL
authors.lastname: Haine
authors.forename: C W
authors.initials: CW
authors.lastname: Yung
authors.forename: Y
authors.initials: Y
authors.lastname: Catoira
authors.forename: H J
authors.initials: HJ
authors.lastname: Garzozi
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D002245:Carbon Dioxide; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology; D009880:Ophthalmic Artery / Q000502:physiology*; D012039:Regional Blood Flow; D012161:Retinal Artery / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology
chemical_list: D002245:Carbon Dioxide