A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment

Use of colour Doppler imaging in ocular blood flow research

The main objective of this report is to encourage consistent quality of testing and reporting within and between centres that use colour Doppler imaging (CDI) for assessment of retrobulbar blood flow. The intention of this review is to standardize methods in CDI assessment that are used widely, but not to exclude other approaches or additional tests that individual laboratories may choose or continue to use.

Normal reference intervals and ranges of side-to-side and day-to-day variability of ocular blood flow Doppler parameters

The study presents normal reference intervals and ranges of "normal" side-to-side and day-to-day variability of ocular blood flow Doppler parameters. Peak-systolic (PSV), end-diastolic velocity (EDV) and impedance indices in the ophthalmic artery (OA), the central retinal artery (CRA) and the short posterior ciliary artery (SPCA) of both orbits were determined with color-coded duplex sonography in 140 healthy volunteers (range 18 to 83 y; 68 men and 72 women). Decreases in flow velocities and concomitant increases in impedance indices were found in all arteries with advancing age. The PSV and the EDV values for the OA, the CRA and the SPCA in the age group less than 40 yr-old were 40.6 +/- 8.9 and 11.2 +/- 3.7, 9.9 +/- 1.8 and 3.7 +/- 0.9, 13.8 +/- 2.6 and 5.7 +/- 1.5 cm/s (mean +/- SD), respectively. In the 40 to 60 yr-old age group, the values were 35 +/- 7.9 and 10.7 +/- 4.3, 9.7 +/- 2 and 3.5 +/- 0.8, 13.5 +/- 2.9 and 5.3 +/- 1.5 cm/s. In the age group over 60 yr-old, the values were 34 +/- 8 and 8.4 +/- 3.3, 9.3 +/- 2 and 3 +/- 0.9, 12.8 +/- 2.4 and 4.3 +/- 1.2 cm/s. In the youngest age group, the EDV in the CRA and the SPCA was higher in women, while in the OA the PSV and the EDV were higher in men. Ranges of side-to-side variability in the OA, the CRA and the SPCA, determined with repeatability coefficient for the PSV and the EDV, were 24, 5.4, 7.5 cm/s and 11, 2.5, 4.2 cm/s, respectively, whereas the values for day-to-day variability were 16.8, 4.3, 6.7 cm/s and 5.6, 1.7 and 3.9 cm/s. Ocular blood flow Doppler parameters range widely and are significantly age and sex dependent. Ranges of "normal" side-to-side and day-to-day variability of the parameters can help to determine abnormal flow pattern.

Comparison of colour Doppler imaging and retinal scanning laser fluorescein angiography in healthy volunteers and normal pressure glaucoma patients

PURPOSE

To correlate retinal circulatory measurements using scanning laser fluorescein angiography and flow velocities of retrobulbar vessels measured by means of colour Doppler imaging.

METHODS

Fifteen patients with normal pressure glaucoma (NPG) and 15 healthy volunteers underwent colour Doppler imaging and fluorescein angiographic studies. Peak systolic velocities (PSVs), end-diastolic velocities (EDVs) and resistive indices (RIs) of the ophthalmic artery (OA) and central retinal artery were obtained. In the fluorescein angiograms arteriovenous passage time (AVP) was quantified by means of digital dye dilution curve analysis.

RESULTS

Arteriovenous passage time was significantly prolonged in NPG patients compared to healthy subjects (p = 0.0026). In the central retinal artery PSV (p = 0.023) and EDV (p < 0.0001) were significantly decreased and RI was increased (p < 0.0001) in patients with NPG. The EDV of the central retinal artery showed a significant correlation with AVP (EDV: r = - 0.53, p = 0.0023). The RI of the central retinal artery correlated significantly to AVP (RI: r = 0.63, p < 0.0001). The AVP did not correlate to EDV or PSV, nor to the RI measured in the ophthalmic artery.

CONCLUSION

Arteriovenous passage time, which represents blood flow in a vascular segment of artery, capillary bed and corresponding vein, was found to be correlated to the EDV and the RI of the central retinal artery. The combination of different techniques allows further interpretation of ocular circulatory responses.

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 (PSV(CRA): r = -0.41; EDV(CRA): r = -0.34), with the PSV and EDV of the NPCA (PSV(NPCA): r = -0.34; EDV(NPCA): 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 (RI(NPCA): r = 0.28; RI(TPCA): 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.

Color Doppler imaging of orbital vessels: personal experience and literature review

Many Doppler imaging studies have been performed in recent years in a large number of ocular disorders because of improvements in the Doppler equipment used for detecting and measuring the low blood-flow velocities that are a requisite for the quantitative evaluation of blood flow in the orbital vessels. The ophthalmic artery, central retinal artery and vein, posterior ciliary arteries, and the superior ophthalmic vein can be easily identified using color Doppler sonography. The changes in local blood flow in these vessels assessed by spectral analysis pulsed Doppler sonography have been used to characterize and to obtain new insights into different nontumoral vascular disorders including carotid artery stenosis, central retinal vein occlusion, giant cell arteritis, glaucoma, diabetes, fistulas, and tumoral processes of the eye and orbit. Our experience has confirmed the important role of Doppler sonography in the assessment of subclinical changes in the vascular bed, in the understanding of different processes, for following up after specific treatments, and for determining the long-term prognosis of these various conditions.

The effects of carotid endarterectomy on ocular haemodynamics

PURPOSE

To determine the profile of blood flow velocities and resistive indices in the ocular vessels of patients with atherosclerotic carotid disease and characterise the effect of endarterectomy on these parameters.

METHODS

Following a preliminary study on healthy volunteers, ophthalmic colour Doppler ultrasound examinations were performed on 27 male and 11 female patients with carotid disease. These measurements were compared with central retinal artery perfusion pressures and intraoperative internal carotid artery stump pressures.

RESULTS

Significant changes were seen on the endarterectomised side. The peak systolic velocity in the ophthalmic artery, and resistive indices in the ophthalmic artery, central retinal artery and nasal posterior ciliary artery, rose from pre-operative values. No correlation between colour Doppler ultrasound measurements and intraoperative internal carotid artery stump pressures was present. When compared with ophthalmodynamometry readings, a relationship was noted with maximum velocities in the central retinal vein.

CONCLUSION

Carotid endarterectomy alters the haemodynamics in selected vessels of the ocular circulation as measured by colour Doppler ultrasound, but more work is required to determine the clinical utility of this investigative modality.

Relation between pressure determined by ophthalmodynamometry and aortic pressure in the dog

AIMS

Ophthalmodynamometry has been used extensively since the last century; however, controversy surrounds what it actually measures. This study was set up to determine the relation between ophthalmodynamometric (ODP) and systemic blood pressures.

METHODS

Aortic pressure was continuously monitored and altered by phlebotomy in six anaesthetised dogs, while ophthalmodynamometry was performed, by directly altering intraocular pressure. Maxillary artery pressure was monitored in two animals. All pressure transducers were zeroed at eye level.

RESULTS

Mean ODP was 96.6% (1.6%) (95% confidence interval, n = 49) of aortic pressure. Mean maxillary artery pressure was 95.7% (5.5%) (95% CI, n = 16) of aortic pressure. ODP was 1.9 (0.6) mm Hg (95% CI, n = 33) higher than maxillary artery pressures.

CONCLUSION

ODP was only slightly below aortic pressure and not significantly different from maxillary artery pressure, the analogue of the internal carotid artery in humans. These results also suggest a retinal artery collapse pressure of at least 1.9 mm Hg.

Color Doppler ultrasound imaging of the eye and orbit

Color Doppler imaging is a non-invasive ultrasound procedure which permits simultaneous gray scale imaging of structure and color-coded imaging of blood velocity. This improved technique allows the user to identify even very small blood vessels, such as those supplying the eye, from which measures of blood velocity and vascular resistance can be obtained. In the past five years, color Doppler imaging has found a number of applications in ophthalmology. A common examination procedure and expected normal values have been established, and the technique is becoming routinely employed to evaluate orbital vasculature in some medical centers. Color Doppler imaging has successfully demonstrated changes in orbital hemodynamics associated with a variety of pathological conditions, including central retinal artery and vein occlusions, cranial arteritis, nonarteritic ischemic optic neuropathy, and carotid disease. In addition, the method has been used to detect the vascularization of orbital and ocular tumors, as well as to investigate altered hemodynamics associated with diseases such as glaucoma and diabetic retinopathy.