Colour Doppler imaging and fluorescein filling defects of the optic disc in normal tension glaucoma

Aim: To investigate the relation between blood flow parameters of the retrobulbar vessels measured by means of colour Doppler imaging (CDI) and fluorescein filling defects of the optic nerve head in patients with normal tension glaucoma (NTG) and control subjects. Methods: 29 patients with NTG and 29 age and sex matched control subjects were included in this study. Blood flow velocities - peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive indices ( RI) of the ophthalmic artery (OA), the central retinal artery (CRA), and of the temporal and nasal short posterior ciliary arteries (TPCA, NPCA) - were measured with CDI. Fluorescein angiograms were performed with a scanning laser ophthalmoscope. The extent of absolute fluorescein filling defects of the optic nerve head in relation to the optic nerve head was assessed. Results: The PSV of the OA, the PSV and EDV of the CRA, and of the TPCA and NPCA were significantly reduced in NTG ( p< 0.05). The RI of the CRA, the TPCA and NPCA were significantly increased in NTG ( p< 0.01). The optic nerve head fluorescein filling defects were significantly larger in NTG ( p< 0.01). The filling defects were significantly negatively correlated ( p< 0.05) with the PSV and EDV of the CRA (PSVCRA: r= - 0.41; EDVCRA: r= - 0.34), with the PSV and EDV of the NPCA (PSVNPCA: r= - 0.34; EDVNPCA: r = - 0.38), and with the EDV of the TPCA ( r = - 0.29). A significant positive correlation ( p< 0.05) was found with the RI of both PCAs (RINPCA: r= 0.28; RITPCA: r= 0.29). Conclusion: Patients with NTG had reduced blood flow velocities and higher resistive indices in most retrobulbar vessels. Optic nerve head fluorescein filling defects were larger compared to controls. The filling defects were correlated with end diastolic velocities and resistive indices of the PCAs and with blood flow velocities of the CRA. Capillary loss of the optic nerve head may be related to higher downstream resistance and reduced blood flow velocities of the retrobulbar vessels.