Hypercapnia and Retrobulbar Blood Flow Velocities in Normal Tension Glaucoma and Healthy Controls
Plange N.1, Kaup M.1, Harris A.2, Remky A.1, Arend O.1
1Augenklinik des Universitätsklinikum Aachen, Germany; 2Dept. of Ophthalmology, Physiology and Biophysics, Indiana University, Indianapolis/USA
Purpose: To evaluate vasoreactivity of retrobulbar vessels provoked with hypercapnia. In Normal Tension Glaucoma (NTG) an impaired vasodilatory response upon CO2-provocation is postulated triggering a deficient capacity of blood flow regulation.
Method: Fifteen patients with NTG (57 ± 12 years) and fifteen age-matched healthy subjects (55 ± 14 years, p=0.55) were included in a prospective study. Blood flow velocities (peak systolic velocity PSV, end diastolic velocity EDV) and resistive indices (RI) of the ophthalmic artery and the central retinal artery were measured with color Doppler Imaging (CDI). Blood flow velocities were measured under normocapnic and hypercapnic isooxemic conditions (increasing the end-tidal pCO2 by 15%). Blood pressure, respiration rate, and oxygen saturation were monitored.
Results: The PSV, EDV and the RI of the ophthalmic artery didnt show any significant differences under normocapnic and hypercapnic conditions for NTG and controls. The PSV and EDV of the central retinal artery were significantly reduced during baseline examination in NTG (p<0.05) compared to controls. The PSV and EDV of the central retinal artery increased significantly more
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