Abstract
Purpose::
To compare ocular pulse amplitude (OPA) and retrobulbar flow velocities between healthy subjects and patients with normal tension or high tension glaucoma. Correlations between OPA and color Doppler Imaging (CDI) parameters and intra-observer and inter-observer reproducibility were analyzed.
Methods::
CDI and OPA measurements were performed twice with one month interval in normal tension (n=30) and high tension (n=18) glaucoma patients and healthy controls (n=22). The peak systolic velocity (PSV) end diastolic velocity (EDV) and the resistive index (RI) of the central retinal artery, temporal and nasal short posterior ciliary and ophthalmic arteries was determined. The CDI readings were performed by the same unmasked observer as well as a masked reading center. A multivariate model was used to compare the OPA and flow velocities between the different diagnostic groups. Correlations were assessed with Spearman analysis.
Results::
OPA was significantly reduced in patients with normal tension (p=0.018) as well as high tension glaucoma (p=0.026) after correction for intraocular pressure (IOP), pachymetry and Tukey adjustment. Blood flow velocities were attenuated in all four retrobulbar vessels in both normotensive (p<0.0001-0.016 for PSV and <0.004-0.048 for EDV) as well as high tension glaucoma (p<0.0001-0.059 for PSV and <0.0001-0.029 for EDV) compared to healthy controls. These differences were consistent after correction for IOP, pachymetry, blood pressure and ocular perfusion pressure. A correlation was observed between the OPA and the systole/diastole ratio as well as the resistive index in controls in all measured blood vessels (ICC=0.42-0.53; p=0.014-0.059). This correlation was not obvious in the glaucomatous patients. CDI measurements were comparable between the two study visits (ICC=0.905-0.711 for PSV; 0.828-0.746 for EDV). Moreover, CDI analysis by the masked reading center resulted in values that were statistically comparable to those obtained by the observer (ICC=0.998-0.996 for PSV; 0.996-0.988 for EDV).
Conclusions::
OPA and blood flow velocity parameters are significantly reduced in normal tension as well as high tension glaucoma patients. OPA and CDI parameters weakly correlate in healthy individuals, but not in glaucoma patients. Retrobulbar CDI readings are reproducible over time as well as between reading centers.
Keywords: optic flow • blood supply • choroid