title: Effect of carbogen, oxygen and intraocular pressure on Heidelberg retina flowmeter parameter 'flow' measured at the papilla.
abstract: The aim of the study was to evaluate whether the Heidelberg retina flowmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after breathing 5% carbogen, (2) at baseline and after breathing 100% oxygen and (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The changes in the value of the HRF parameter 'flow' were analyzed by means of a paired Student's t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7+/-2.5% (mean+/-SEM) in HR parameter 'flow' (p < 0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3+/-2.6% in HRF parameter 'flow' (p = 0.024). Increasing IOP to 20 mm Hg did not result in a statistically significant change in HRF parameter 'flow' (-9.6+/-7.4%; p = 0.13). Increasing IOP from 20 to 50 mm Hg, however, resulted in a statistically significant decrease of 40.1+/-6.6% in HRF parameter 'flow' (p = 0.003). With the applied stimuli, the HRF parameter 'flow' changed in the expected direction, i.e. an increase with hypercapnia and a decrease with hyperoxia or high IOP. The simplicity of use of the HRF instrument suggests that it might be well suited for a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.
authors.affiliation: Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Lietz
authors.forename: P
authors.initials: P
authors.lastname: Hendrickson
authors.forename: J
authors.initials: J
authors.lastname: Flammer
authors.forename: S
authors.initials: S
authors.lastname: Orgül
authors.forename: I O
authors.initials: IO
authors.lastname: Haefliger
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D002245:Carbon Dioxide / Q000008:administration & dosage*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D018496:Hyperoxia / Q000503:physiopathology; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D009798:Ocular Hypertension / Q000503:physiopathology; D009898:Optic Disk / Q000098:blood supply*; D009900:Optic Nerve / Q000098:blood supply; D010100:Oxygen / Q000008:administration & dosage*
chemical_list: D002245:Carbon Dioxide; C011700:carbogen; D010100:Oxygen