Abstract
Abstract: :
Purpose: Beside the intraocular pressure, changes in ocular hemodynamics were shown to play a critical role in the pathogenesis of glaucoma. Volumetric Color Doppler Imaging (vCDI) has been suggested as suitable method for determination of ocular blood volume per time. In the present study we evaluate the feasibility of vCDI for clinical use. We hypothesize that with CDI it should be possible to estimate reliably the diameter of the ophthalmic artery (OA) and the central retina artery (CRA) in glaucoma patients. We calculated the blood volume per time from velocity and diameter. Methods: In 20 patients reproducibility and observer dependence of results were studied. In 69 patients vCDI results were compared to readings from Langham ocular blood flow system (LOBF). In 15 patients vCDI measurements were performed before and in presence of dorzolamide, a local inhibitor of the carbonic anhydrase, which has been shown previously to increase ocular blood flow (OBF). These experiments were undertaken to evaluate if changes in OBF were detected by vCDI. Results: Measurements of velocities using CDI in OA and CRA were highly reproducible (n=20, Single Measure Intraclass Correlation (SMIC) >0.70 for all parameters) and independent of the investigator (n=20, paired t–test P>0.50 for all parameters). In contrast, a low reliability in measuring diameter (n=20, paired t–test OA P=0.01, CRA P<0.01), and consequently in volume were found when single measurements were performed (n=20, paired t–test OA P=0.02, CRA P=0.002). Good reliability was reached when 5 consecutive measures were averaged. We found no correlation between the CDI parameters and the LOBF (n=69, Spearman correlation coefficient AO R=–0.015 P=0.19; CRA R=–0.03, P=0.80). Dorzolamide accelerated OBF in long and short ciliary arteries (n=15, paired t–test P<0.05). In contrast, volume determined by vCDI remained unchanged. Conclusions: Single vCDI measurements have a low reproducibility, so that there is the need to average 5 measurements to achieve adequate reproducibility. The vCDI measurements did not correlate with LOBF. The vCDI failed to detect alteration of ocular perfusion induced by dorzolamide. In conclusion, due to its insufficient reliability, vCDI it is not appropiate for clinical and scientific use at present.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • neuroprotection • optic flow