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S. T. Venkataraman, C. Hudson, J. A. Fisher, R. Rachmiel, T. Ahmed, Y. Buys, G. Trope, J. G. Flanagan; Retinal Arteriolar and Capillary Response to Isoxic Hypercapnia in Primary Open Angle Glaucoma Pre- & Post-Treatment. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4395.
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To investigate the magnitude of retinal arteriolar and capillary vascular reactivity in response to isoxic hypercapnia in patients with untreated, newly diagnosed POAG (uPOAG) and progressive POAG (pPOAG), and to determine the magnitude of vascular reactivity after treatment with Dorzolamide in uPOAG.
Seven patients with uPOAG (mean age 52 yrs, range 27-65 yrs), 9 patients with pPOAG defined by the recent occurence of optic disc hemorrhage (mean age 65 yrs, range 52-76 yrs) and 11 controls (mean age 53 yrs range 44-63yrs) were studied. Isoxic hypercapnia (i.e. a 15% increase in PETCO2) was induced using a computer driven gas flow controller. Retinal hemodynamic measurements were acquired at baseline and during isoxic hypercapnia using the Canon Laser Blood Flowmeter (CLBF) and Heidelberg Retina Flowmeter (HRF). Patients with uPOAG were then treated with Dorzolamide 2% for 2 weeks and retinal vascular reactivity assessment was repeated at the end of this regime.
Group mean retinal arteriolar diameter increased by 2 to 3% in both groups of patients with POAG and controls. Group mean arteriolar blood velocity increased by 3%, 10% and 17% during isoxic hypercapnia in uPOAG, pPOAG and controls, respectively, while group mean blood flow increased by 8%, 15% and 22%. Group mean capillary blood flow at the temporal rim of the optic nerve head (ONH) increased by 12%, 4% and 20% during isoxic hypercapnia in uPOAG, pPOAG and controls, respectively. Following treatment with Dorzolamide in uPOAG, there was a 5%, 17% and 25% increase in the group mean retinal arteriolar diameter, blood velocity and blood flow respectively, in response to isoxic hypercapnia. Group mean capillary blood flow at the temporal rim of the ONH also increased by 25%.
Patients with uPOAG showed a reduced magnitude of change in arteriolar blood flow to isoxic hypercapnia compared to the other groups, while patients with pPOAG showed a reduced magnitude of change in capillary blood flow at the ONH. These early results suggest that treatment with Dorzolamide improves retinal arteriolar and capillary vascular reactivity in patients with uPOAG.
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