[The effect of carbon dioxide on intraorbital hemodynamics in glaucoma determined by color Doppler imaging]

We developed a new system to safely supply carbon dioxide (CO2) to man to investigate the effect of the gas vasodilator on orbital blood flow in open angle glaucoma (OAG) patients. Using the system, we determined orbital hemodynamics in OAG by color Doppler imaging (CDI) at baseline conditions and during CO2 supplementation sufficient to increase end-tidal CO2% by 10%. Seven OAG patients (mean age, 60.9 +/- 16.4 years; normal-tension glaucoma/primary open-angle glaucoma = 5/2) were included in the study. CDI was performed to measure resistance index (RI), and peak-systolic and end-diastolic blood flow velocities (PSV & EDV) of the ophthalmic artery (OA) and the central retinal artery (CRA). Systemic conditions including oxygen saturation and blood pressure were monitored throughout the period of the CO2 inhalation. CO2 significantly increased PSV and EDV in the CRA (p = 0.0273, p = 0.0094, respectively; Wilcoxon signed-rank test), but not in the OA. Other parameters were not altered. The results suggest that CO2 inhalation increases blood flow velocities in distal arteries in OAG patients without affecting proximal vessels. The new system enables us to supply CO2 in a safe and controlled manner in glaucoma patients and to modify orbital hemodynamics.