Hemodynamic alterations in the acute retinal necrosis syndrome

Color Doppler Ultrasound in Ocular Behçet's Disease

The purpose of this study was to evaluate the hemodynamic changes occurring in the ophthalmic vasculature of eyes with Behçet's disease in a controlled clinical trial.

Both eyes of patients with retinal involvement due to Behçet's disease were consecutively evaluated and were established as having mild or severe retinal vasculitis according to the ophthalmoscopic and fundus fluorescein angiographic findings. One eye from each patient was randomly selected and 25 eyes with mild to moderate and 25 eyes with severe vasculitis were identified. Color Doppler imaging (CDI) was used to quantitate blood flow velocities and vascular resistance in the ophthalmic artery (OA), central retinal artery (CRA) and central retinal vein (CRV) of these patients and those of 25 healthy volunteers. All three groups were age- and sex-matched.

In the OA, peak systolic, end diastolic and average flow velocities were significantly higher in patients with Behçet's disease than in the control group (p<0.05). CRA blood flow velocities of patients with severe retinal involvement were significantly lower than those with mild to moderate vasculitis and control groups and the average vascular resistance was significantly higher than in the control group (p<0.05). Additionally, the average blood flow velocities in the CRV of patients with severe vasculitis were significantly lower than in mild to moderate vasculitis and control patients.

Marked circulatory changes were seen in the ophthalmic vasculature of eyes with Behçet's disease. Although larger studies are required to define the true sensitivity and specificity of this technique, these initial results suggest that CDI could play a major part in the assessment of patients with ocular Behçet's disease.

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.

Analysis of retinal findings of acute retinal necrosis using optical coherence tomography

PURPOSE

To analyze the retinal findings in patients with ARN, optical coherence tomography (OCT) was performed.

METHODS

Seven patients (7 eyes) with ARN were studied using OCT.

RESULTS

OCT images depicted highly reflective areas in the inner layers of the retina in all seven cases, corresponding with the yellowish-white lesions of the retina in the acute phase. Disorganization of the retinal structure was also observed in these retinal lesions, especially in cases with severe inflammation. Subretinal changes including retinal exudate and/or fluid were observed in only one case. After regression of the yellowish-white lesions in the retina, a significant reduction in retinal thickness was observed on OCT.

CONCLUSIONS

OCT permits the detection of full-thickness retinal necrosis in the acute phase and complete absence of retinal structure in the resolution phase, corresponding with the yellowish-white lesions seen in patients with ARN.

Investigation of hemodynamic changes after strabismus surgery using color Doppler imaging

PURPOSE

To investigate hemodynamic changes after strabismus surgery using color Doppler imaging (CDI).

METHOD

Group 1 patients (n = 13) underwent surgery on a single horizontal rectus muscle, and group 2 (n = 13) underwent surgery on both horizontal rectus muscles. Subjects with no systemic or ophthalmologic disorders were selected as controls (n = 16). In group 1 and group 2, CDI of the ophthalmic artery (OA), the central retinal artery (CRA), and the nasal and temporal posterior ciliary arteries (PCAs) was performed before surgical correction and on postoperative days 1 and 7. For each vessel, peak systolic (V(max)), end diastolic (V(min)), and mean (V(mean)) blood flow velocities were measured, in addition to the resistivity index (RI) and pulsatility index (PI).

RESULTS

V(max) in the OA on postoperative day 1 was higher in group 2 than in group 1 (P =.004). V(min) in the OA on postoperative day 1 was significantly higher in group 2 than in the controls (P =.001) and group 1 (P =.001). For group 2, comparison of the OA preoperative findings to the findings on postoperative day 1 showed that V(min) (P =.003) and V(mean) (P =.02) increased significantly, and the RI (P =.01) and PI (P =.006) decreased significantly. These significant differences were not observed on day 7 (P >.05).

CONCLUSION

Surgery on both horizontal rectus muscles in an eye causes hemodynamic changes in the OA in the early postoperative period.

Use of color doppler imaging for determining the resistive index of the medial long posterior ciliary artery in clinically normal conscious dogs

OBJECTIVE

To evaluate the use of color Doppler imaging (CDI) for determining the resistive index (RI) of the medial long posterior ciliary artery (mLPCA) in clinically normal conscious dogs.

ANIMALS

18 (10 sexually intact males, 8 sexually intact females) dogs between 1 and 5 years old.

PROCEDURE

Color Doppler ultrasonography was performed on both eyes with dogs in a sitting position. Each eye was imaged from the region dorsal to the zygomatic arch with the transducer positioned in a horizontal plane. The mLPCA was localized, and RI was calculated from velocities obtained for 3 similar Doppler waveforms. To determine the reproducibility of CDI-derived RI, measurements were repeated twice at a 10-day interval.

RESULTS

Mean (+/- SD) RI of the mLPCA was 0.68 +/- 0.07 (95% confidence interval, 0.65 to 0.70; n = 36 eyes). Resistive index did not significantly differ between right and left eyes or male and female dogs. In addition, body weight was not correlated with RI. Repeated measurements of RI did not yield significantly different results (interclass correlation coefficient, 0.8297).

CONCLUSION AND CLINICAL RELEVANCE

Color Doppler imaging appears to be a valid technique for determination of RI of the mLPCA in conscious dogs. This technique may be useful for investigating the pathophysiologic processes of many ocular and orbital vascular disorders in dogs.

Arterial blood flow characteristics in central retinal vein occlusion and effects of panretinal photocoagulation treatment: an investigation by colour Doppler imaging

AIMS

To determine whether an increase in vascular resistance in the central retinal and ophthalmic arterial circulations contributes to the development of central retinal vein occlusion (CRVO), or haemodynamic alterations in central retinal and ophthalmic arteries occur secondary to the vein occlusion as increased intravascular pressure is transferred through the capillary bed to the arterial side and the effect of panretinal photocoagulation treatment on these circulations in ischaemic cases.

METHODS

The ophthalmic and central retinal arteries of the affected and non-affected eyes of 20 patients with non-ischaemic CRVO, 13 patients with ischaemic CRVO, and 22 control subjects were investigated by colour Doppler imaging. Panretinal photocoagulation (PRP) treatment was applied to the eyes with ischaemic CRVO. Maximum and minimum blood flow velocities, and resistivity indexes were calculated in the affected and healthy eyes of patients and in the control eyes.

RESULTS

Average blood flow velocity in the central retinal and ophthalmic arteries of patients with non-ischaemic CRVO did not differ from their fellow eyes, but a significantly lower average blood flow velocity was found in the ophthalmic and central retinal arteries of the patients with ischaemic CRVO compared with their fellow eyes. Patients with ischaemic CRVO had significantly lower blood flow velocities in their ophthalmic and central retinal arteries than non-ischaemic cases that were further reduced following PRP treatment.

CONCLUSION

This study suggests that impaired arterial blood flow observed in patients with CRVO may be partly related to secondary changes in the retrobulbar arterial circulation as a result of enhanced arterial resistance following CRVO. These data also demonstrate that PRP treatment decreases retinal and ophthalmic blood flow velocities in patients with ischaemic CRVO.

Hemodynamic alterations in diabetic retinopathy

PURPOSE

This study was designed to examine the characteristics of retrobulbar circulation and the role of glycemic control in patients with diabetes and varying stages of retinopathy.

METHODS

Seventy-three eyes in 37 patients with diabetes were assigned to one of the following four study groups: nonproliferative diabetic retinopathy (non-PDR), proliferative diabetic retinopathy (PDR), post-panretinal photocoagulation (PRP), or preretinopathy (the control group). Color Doppler imaging was used to quantitate peak systolic blood flow velocities of the central retinal artery (CRA), the central retinal vein (CRV), the posterior ciliary artery (PCA) and the ophthalmic artery. Glycated hemoglobin (HbA1c) levels were used as an indicator of glycemic control.

RESULTS

The authors found that the CRA maximum blood flow velocity levels were significantly higher in the pre-retinopathy group (9.8 +/- 2.1 cm/second) than in the non-PDR group (8.1 +/- 2.2 cm/second). In addition, the CRV maximum blood flow velocity levels were significantly higher in the pre-retinopathy group (5.7 +/- 0.9 cm/second) than in both the PDR group (4.8 +/- 1.5 cm/second) and the PRP group (4.9 +/- 1.7 cm/second). No significant differences were seen in blood flow velocity levels of the ophthalmic artery and the PCA among the retinopathy groups. No correlation was found between HbA1c levels and the stage of retinopathy. The presence of systemic hypertension showed no significant effect on blood flow velocities in the various retinopathy groups.

CONCLUSION

This study demonstrates the presence of some circulatory changes in the CRA and the CRV in patients' eyes with diabetic retinopathy when compared with patients' eyes in the pre-retinopathy stage of the disease. These data support the contention that changes in retrobulbar circulation and microcirculation occur during the pathogenesis of diabetic retinopathy. The clinical significance of these findings needs to be determined.

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.

Measurement of ocular blood flow velocity using colour Doppler imaging in low tension glaucoma

The purpose of this study was to compare the velocity of blood flow and vascular resistance measured by colour Doppler imaging in the ophthalmic and central retinal arteries in 34 eyes of 34 patients (mean age 68.1 years) with low tension glaucoma (LTG) and 17 eyes of 17 age-matched normal controls (mean age 65.2 years). The Acuson 128 machine (using a 7.5 MHz probe) was used to measure peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI). The EDV of the ophthalmic artery (OA) in the LTG was significantly (p = 0.04) less than in the normal control group. There was a significant (p = 0.02) increase in the vascular RI of both the OA and central retinal artery in the LTG group compared with the normal controls. The OA RI increased with age (r = 0.61, p = 0.0001), and the OA EDV decreased with age (r = -0.50, p = 0.003), in the LTG group but not in the normal control group. The results suggest an increased resistance to blood flow in the ophthalmic and central retinal arteries of LTG patients.