Abstract
Purpose: :
To investigate the reproducibility of color Doppler imaging (CDI) measurements performed on primary open angle glaucoma (OAG) patients participating in the Indianapolis Glaucoma Progression Study (IGPS).
Methods: :
Retrobulbar blood flow velocities and Pourcelot’s vascular resistance index (RI) in OAG patients were measured with CDI as part of the IGPS. Two baseline measurements were obtained 1-2 weeks apart at the same time of day for all participants. Peak systolic and end diastolic blood flow velocities (PSV/EDV) were measured in the ophthalmic (OA), central retinal (CRA), and nasal and temporal short posterior ciliary arteries (N/TPCA) and RI was calculated. Reproducibility of CDI was assessed by estimating the intra-class correlation coefficient (ICC) and 95% confidence intervals (CI) between the two measurements. Limits of agreement were determined for quantifying the stability of the data. Bland-Altman plots of the difference between the two measurements versus the average of the two measurements for each parameter were created.
Results: :
93 patients were examined to date with a mean age of 65.8 (SD9.9) years (58% female). In the OA the ICC for the PSV, EDV, and RI were 0.939 (0.908-0.959), 0.885 (0.826-0.923), and 0.914 (0.870-0.943), respectively. In the CRA the ICC for the PSV, EDV, and RI were 0.882 (0.822-0.922), 0.763 (0.642-0.843), and 0.900 (0.849-0.943). The ICC for the PSV, EDV and RI were 0.931 (0.896-0.954), 0.902 (0.852-0.935), 0.835 (0.751-0.890) in the NPCA and 0.927 (0.891-0.952), 0.934 (0.901-0.956), 0.919 (0.877-0.946) in the TPCA, respectively. Natural variation was largest for OA PSV (4.0) and smallest for TPCA RI (0.028).
Conclusions: :
In this study CDI measurements of the OA, CRA and PCAs conducted at one to two week intervals were shown to be highly reproducible. The analysis suggests a trained CDI operator can reliably measure the retrobulbar blood vessels in OAG patients.
Keywords: blood supply • imaging/image analysis: non-clinical • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology