title: The effect of caffeine on retrobulbar hemodynamics.
abstract: BACKGROUND
  To investigate the acute effect of caffeine on intraocular pressure and retrobulbar blood flow velocity.
  
  
  METHODS
  In this randomized, double-masked, placebo-controlled, prospective study, we examined the effects of single 300-mg oral administration of caffeine on retrobulbar arteries' hemodynamics by using color Doppler ultrasonography imaging in healthy human volunteers. The subjects were divided into two groups; group 1 received a 300-mg caffeine tablet and group 2 received placebo. Measurements were obtained in two eyes at baseline, and 1 hr after acute ingestion of caffeine. Blood pressure, pulse rate, and intraocular pressure were monitored.
  
  
  RESULTS
  When compared with placebo, no significant change in mean blood pressure or intraocular pressure was observed after administration of caffeine. No significant differences were detected in the peak systolic and end diastolic velocities of retrobulbar arteries, compared with baseline values. Resistive index of ophthalmic, central retinal, and short posterior nasal ciliary artery were significantly increased after oral application of caffeine in group 1 (p<0.05).
  
  
  CONCLUSIONS
  The vascular resistance of the retrobulbar vessels appears to be altered by caffeine consumption. Further studies are needed to investigate the effects of caffeine on hemodynamics in patients with glaucoma.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Kocaeli University, Kocaeli, Turkey. aydoganberna@yahoo.com
authors.forename: Berna
authors.initials: B
authors.lastname: Ozkan
authors.forename: Nurşen
authors.initials: N
authors.lastname: Yüksel
authors.forename: Yonca
authors.initials: Y
authors.lastname: Anik
authors.forename: Ozgul
authors.initials: O
authors.lastname: Altintas
authors.forename: Ali
authors.initials: A
authors.lastname: Demirci
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Cağlar
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D019842:Ciliary Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging / Q000502:physiology; D009915:Orbit / Q000098:blood supply*; D011446:Prospective Studies; D012161:Retinal Artery / Q000000981:diagnostic imaging / Q000502:physiology; D018615:Ultrasonography, Doppler, Color
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine