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Luis Abegao Pinto, Evelien Vandewalle, Anke Pronk, Maudgal Prabhat, Ingeborg Stalmans; Retrobulbar Flow Velocities Reveal Different Responses To Changes In Resistance Index Between Glaucomatous And Healthy Subjects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3485.
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To characterize pulsatility index (PI) and mean flow velocities (MFV) of the retrobulbar arteries by color Doppler imaging (CDI) in eyes with primary open angle glaucoma (POAG). To investigate the relation between MFV and PI with the arteries’ resistance index (RI).
Retrospective analysis of CDI examinations by patients with POAG (n=49), normal tension glaucoma (NTG, n=62) and healthy controls (n=48). MFV and PI of the central retina artery (CRA), nasal posterior ciliary artery (NPCA), temporal posterior ciliary artery (TPCA) and ophthalmic artery (OA) of the worst affected eye were calculated by a condition-masked investigator.
RI and PI of the CRA, NPCA, TPCA and OA were similar between the three groups (p>0.05 in all group comparison). MFV were lower in POAG and NTG versus controls in CRA, NPCA and TPCA (p<0.005 on all arteries), but not in the OA (p=0.30). The relation between the MFV and PI with RI were different between the groups. A positive correlation between RI/MFV was detected in the CRAs of NTG (r=0.33, p=0.008) and POAG(r=0.47, p<0.001), which was not observed in the control group (p=0.71). In the other arteries (NPCA, TPCA and OA) however, all three groups showed a similar RI/MFV relation. Nevertheless, while in OA this was a negative RI/MFV correlation (p<0.02 in all groups), we couldn’t find any relation between these variables in NPCA nor TPCA (p>0.05 in all groups). PI and RI were positively correlated in all four arteries in all NTG, POAG and control groups (p<0.0001).
Our data suggests that glaucoma patients have a different response to increased arterial resistance when compared to healthy controls. This response is not the same in all arteries, with CRA and OA showing opposite correlations between MFV and RI. According to perfusion pressure formulas, increases in MFV in face of increased RI, as seen in glaucoma patients CRA, might mean a decrease in vessel section and thus vasoconstriction. Our results suggest that glaucoma patients have an increased vasoconstrictive response when compared to healthy patients. MFV studies can give further insight into ocular circulation dynamics.
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