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Color Doppler velocimetry of the optic nerve head in arterial occlusion
T H Williamson1, G M Baxter, G N Dutton
1Tennent Institute of Ophthalmology, Western Infirmary, Glasgow, UK.
Background:
Color Doppler velocimetry allows simultaneous imaging by B-scan and Doppler ultrasound. This facilitates estimation of blood velocity in the orbital vessels. A pulse arterial waveform providing blood velocity measurements can be obtained from the optic nerve head. The vascular pattern in this region consists of multiple peripapillary blood vessels and a central artery. The exact contribution of the arteries in this area to velocimetry readings was undetermined.
Methods:
In this study, the arterial pulses at the optic nerve head of seven patients with central retinal artery occlusion (CRAO) and seven with anterior ischemic optic neuropathy (AION) were examined by color Doppler velocimetry.
Results:
No velocimetric measurements were obtainable at the optic nerve head in three of four patients with acute CRAO (examined within 24 hours of onset) despite color recordings obtainable in the peripapillary region. In contrast, all patients with AION showed characteristic arterial pulse waveforms from the artery that was situated centrally in the optic nerve. No peripapillary color indices were detectable in three of the four patients with ischemic optic neuropathy who were examined within 24 hours of onset of their symptoms. Follow-up investigation showed that there was reperfusion of both arterial circulations within 1 week.
Conclusion:
The results demonstrate that color Doppler ultrasound of the optic nerve head provides velocimetric measurements of blood flow in the central retinal artery. Although some investigators using different apparatuses have produced velocimetry measurements from the posterior ciliary arteries, in this study reliable measurements were not obtainable form color indices in the peripapillary area.