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Color Doppler ultrasonography has numerous potential applications in the diagnosis and monitoring of many ocular disease processes. One of its advantages over other investigative and diagnostic tests is its safety and repeatability. To be able to fully assess this technique it is important to have good control data and to know the reproducibility of the technique for each of the retrobulbar vessels. Color Doppler ultrasonography was performed on 80 volunteers, and normal ranges of blood velocity were calculated for the ophthalmic artery and for the central retinal artery and vein. Reduction in the peak systolic and end diastolic velocities in the ophthalmic artery and an increase in resistive index in the central retinal artery and vein were noted with advancing age. With regard to reproducibility of the retrobulbar vessels, 15 healthy persons were chosen at random and intra- and interobserver studies performed. The most reliable and reproducible vessels were the ophthalmic artery and central retinal artery and vein. Greater variation was noted in the posterior ciliary vessels, whereas the superior ophthalmic and vortex veins were unreliable in both detection and velocity measurement. The results provide normal ranges for future studies and demonstrate that reproducible results can be obtained for the orbital vasculature using color Doppler imaging.

The influence of multiple systemic factors upon the blood velocities obtained from the orbital circulations was investigated. The velocities obtained by colour Doppler imaging from the ophthalmic artery, central retinal artery, and vein from 95 ophthalmologicaliy healthy volunteers were analysed. The effects of age, systemic blood pressure, and smoking habit were examined. In 24 volunteers blood viscosity was also measured and its relation with blood velocity assessed. Age was weakly negatively correlated with the blood velocities in the ophthalmic artery and weakly positively correlated with resistance to flow in the retinal circulation. Systolic blood pressure showed a positive correlation with the peak systolic velocities in the arteries while cigarette smoking was associated with lower ophthalmic artery velocities. Increased haematocrit and viscosity were positively correlated with resistance to flow proximal to the ophthalmic artery and red cell rigidity negatively correlated with the pulsatility of flow in the retinal vein. These results help to identify the roles of systemic conditions in the ocular circulation. The influence of blood viscosity on retinal venous flow may be relevant to the pathogenetic mechanisms of conditions such as central retinal vein occlusion. (BrJ Ophthalmol 1995; 79: 17-22) Colour Doppler imaging allows examination of the pulsatile velocity of blood in the orbital vessels'"3 and has been used in the investigation of a number of vascular ophthalmic disorders."9 Although the effects of posture3 and intraocular pressure5' 1 have been investigated, the effects of various systemic factors upon the blood velocities obtained by this technique are as yet unknown. In this study the influence of age, systemic blood pressure, smoking habit, and arteriopathy were examined in a control population to determine their effect on these haemodynamic variables.In addition, blood rheology, which may have a profound effect on the blood flow of the eye and has been implicated in number of ophthalmic vascular disorders"-'' was examined in a group of volunteers also examined by colour Doppler imaging. The relation between the rheology of the blood and its pulsatile velocities was therefore investigated and interpreted with reference to the pathogenesis of ocular diseases. Subjects and method SUBJECTSNinety five volunteers were examined to provide control data and consisted of staff of the ophthalmology or radiology department at the Western Infirmary Hospital, Glasgow and relatives of patients attending the ophthalmology outpatient department. The volunteers were asked for history of general medical and ocular conditions, drug usage. Smoking habit was recorded as one ofthe following: (1) Non-smoker, (2) ex-smoker, (3) smokes less than 20 cigarettes each day, (4) smokes at least 20 cigarettes each day, (5) pipe or cigar smoker.

The primary imaging technique in suspected venous occlusive disease has for many years been contrast venography. Recent studies have shown ultrasound with the addition of colour Doppler imaging to be a suitable alternative method in the diagnosis of lower limb venous thrombosis. We have applied these techniques to the upper limb venous system, and have performed a prospective study of 19 patients (30 limbs) comparing colour Doppler ultrasound with venography in the diagnosis of axillary and subclavian vein thrombosis, for which colour Doppler ultrasound has a sensitivity and specificity of 100%. If vein stenosis is included, the sensitivity falls to 89%. We propose that colour Doppler ultrasound is a suitable first-line alternative to venography in the diagnosis of axillary and subclavian vein thrombosis. In addition to showing the major venous drainage of the upper limb, ultrasound routinely assesses patency of the internal jugular vein, which is, on occasion, of clinical relevance when determining possible future sites of venous access. If, however, colour Doppler ultrasound is normal then bilateral upper limb venography is indicated to exclude a more central venous problem or localized stenotic lesion.

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