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Editor,—Takayasu’s arteritis (TA) is a systemic necrotising vasculitis of unknown aetiology whose characteristic ocular manifestations relate to ocular ischaemia. Orbital colour Doppler imaging (CDI) is useful to evaluate haemodynamics of the orbital circulation and its abnormalities.1 We report the ophthalmic artery blood flow in two patients with TA using CDI.
CASE REPORT Case 1
A 34 year old man, previously diagnosed with TA was referred for ophthalmic evaluation. He had absence of radial artery pulses, unrecordable upper extremity blood pressure measurements, lower extremity hypertension, arteriographic evidence of total left brachiocephalic artery occlusion, right brachiocephalic and bilateral common carotid artery stenoses, increased erythrocyte sedimentation rate (11 mm in the first hour), and positive C reactive protein. The best corrected Landolt visual acuity was light perception in the right eye and 0.2 in the left. Intraocular pressures (IOP) were 9 mm Hg in the right eye and 12 mm Hg in the left. Left funduscopy revealed venous dilatations, microaneurysms, and arteriovenous shunts. The arm-retina time was prolonged with wide peripheral avascular areas. Two years later, left iris rubeosis and episcleral vessel dilatation developed. IOP was 20 mm Hg. CDI showed a marked decrease in both the left ophthalmic artery anterograde blood flow and the systolic peak of the arterial waveform (Fig 1). Gosling and King’s pulsatility index (PI) values2 were calculated at 1.0 in the right eye and 0.55 in the left (Table 1).
A 75 year old woman was referred for evaluation. She reported left visual disturbance, was diagnosed as having TA based on systolic blood pressure difference between the arms (right 88/46 mm Hg, left 122/86 mm Hg), a neck bruit, left common carotid artery occlusion, and left subclavian artery stenosis on carotid angiography, and positive HLA assays. The best corrected Landolt visual acuities were 1.0 right eye and 0.02 left. IOP was 6 mm Hg in both eyes. Left eye funduscopy showed inferior optic disc paleness and inferotemporal artery narrowing with a cholesterol plaque. Arm-retina circulation time was delayed. Two years later, left iris neovascularisation developed. IOP was 10 mm Hg. CDI showed reduction in the left ophthalmic artery anterograde blood flow (Table 1). Gosling and King’s PI values were 1.25 right eye and 1.3 left eye.
CDI has only recently been introduced as a useful adjunct to clinical ophthalmological examination.1 Although most useful in the evaluation of vascular disorders, CDI is also of value in the diagnosis of ocular ischaemic syndromes by allowing direct measurement of the waveform of orbital arteries, thus enabling direct assessment of the orbital vascular supply.3-7 The peak systolic flow velocity of the ophthalmic artery in TA was markedly reduced as in patients with carotid atheromas. In ocular ischaemic syndrome secondary to carotid atheroma, the PI is reported to be higher than normal. This is thought to be due to the increase in the peripheral vascular resistance secondary to the arteriosclerotic process involving the orbital vessels.3-7 In contrast, the PI in TA was lower (case 1) or almost normal (case 2) compared with control eyes. Since only large vessels are affected in TA, the peripheral vascular resistance would not be as increased as in carotid atheroma. Moreover, the low PI values in case 1 reflect a decreased peripheral vascular resistance which may be due to the formation of arteriovenous anastomoses in the retina and to the formation of collateral blood flow between the internal and external carotid arteries manifesting as dilated episcleral vessels. In case 2, the lack of arteriovenous anastomosis formation could have resulted in the almost normal PI value despite the decrease in total peripheral ocular vascular resistance.
PI measurements by CDI could be useful in the detection of retrobulbar vessel flow abnormalities, particularly in the ophthalmic artery, and in the evaluation of ocular manifestations in TA.
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