Modulation of Heidelberg Retinal Flowmeter parameter flow at the papilla of healthy subjects: effect of carbogen, oxygen, high intraocular pressure, and beta-blockers.
The Heidelberg Retina Flowmeter (HRF) is intended to assess ocular blood flow by scanning laser doppler flowmetry. In the retina and possibly in the optic nerve head, carbogen increases blood flow, whereas pure oxygen or high intraocular pressure (IOP) decrease it. This study addresses whether at the papilla of healthy volunteers, the HRF parameter flow, is modulated by breathing 5% carbogen (5% carbon dioxide + 95% oxygen) for 7 minutes, breathing 100% oxygen for 7 minutes, increasing IOP to 50 mm Hg with a suction cup, or decreasing IOP with a single topical ocular instillation of the beta-blockers 0.5% betaxolol (betoptic) or 0.5% timolol (timoptic). At the papilla (20 degrees x 5 degrees, 256 X 64 pixels), values of HRF parameter, flow (50 X 50) pixels, increased after carbogen (N = 5, P < 0.05), but decreased after oxygen (N = 5, P < 0.05) or IOP increase (N = 5, P < 0.01). Although IOP values were significantly reduced by betaxolol (N = 9, P < 0.05) and timolol (N = 9, P < 0.01), HRF values were only significantly decreased (N = 9, P < 0.05) after timolol. In conclusion, at the papilla of healthy volunteers, a positive correlation exists between changes in values of the HRF-parameter, flow, and stimuli considered to modulate retinal and ONH blood flow. Furthermore, although of unkown clinical relevance, it appears that in contrast to betaxolol, values of the HRF parameter, flow, at the papilla of healthy volunteers are significantly decreased after a single instillation of timolol.
Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic Basel, Switzerland.
I O
IO
Haefliger
A
A
Lietz
S M
SM
Griesser
A
A
Ulrich
A
A
Schötzau
P
P
Hendrickson
J
J
Flammer
D000280:Administration, Inhalation; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D015784:Betaxolol / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D002245:Carbon Dioxide / Q000494:pharmacology*; D004311:Double-Blind Method; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D009883:Ophthalmic Solutions; D009898:Optic Disk / Q000098:blood supply* / Q000187:drug effects; D010100:Oxygen / Q000494:pharmacology*; D012016:Reference Values; D012161:Retinal Artery / Q000187:drug effects / Q000502:physiology*; D013999:Timolol / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D009883:Ophthalmic Solutions; D002245:Carbon Dioxide; C011700:carbogen; D013999:Timolol; D015784:Betaxolol; D010100:Oxygen