Colour Doppler ultrasonography of the ophthalmic artery: flow parameters in normal subjects. The significance of the resistance index.
BACKGROUND
The aim of this study was to assess the flow characteristics in ophthalmic arteries and to detect their possible relationships to those in the common and internal carotid arteries.


METHODS
Sixty healthy subjects (age range 20-74 years) with normal vascular findings, stratified by age and sex were recruited to the study. A colour Doppler ultrasound examination of the neck arteries was performed, followed by a colour Doppler ultrasound examination of the 120 ophthalmic arteries included. Peak systolic velocity, end diastolic velocity and resistance index (RI) of the common carotid, internal carotid and ophthalmic arteries, as well as the insonation depth of the ophthalmic arteries were measured.


RESULTS
The mean values (standard deviation) of the measured parameters for the ophthalmic arteries were: insonation depth: 38.38 mm (2.60 mm), peak systolic velocity: 34.71 cm/sec (6.38 cm/sec), end diastolic velocity: 7.95 cm/sec (1.70 cm/sec), resistive index: 0.77 (0.04). The resistance index of the ophthalmic arteries was, in all cases, greater than that of the ipsilateral common carotid artery which in turn, was greater than that of the internal carotid. The value of the index in the ophthalmic arteries, when the circulation is normal in the extra- and intracranial arteries is rarely lower than 0.70.


CONCLUSIONS
When an inversion of the ratio between the resistance index of the ophthalmic artery and that of the common carotid or an index value lower than 0.70 in the ophthalmic artery is observed, further investigation is needed as this situation cannot be considered normal. The resistance index seems to be the most reliable parameter for the estimation of normal circulation in ophthalmic arteries.
Kouvidis
G K
GK
Radiology Department, 7th IKA Hospital, Athens, Greece.
Benos
A
A
Kyriakopoulou
G
G
Anastopoulos
G
G
Triantafyllou
D
D
D000328:Adult; D000368:Aged; D002339:Carotid Arteries / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging*; D012039:Regional Blood Flow / Q000502:physiology; D018615:Ultrasonography, Doppler, Color; D014655:Vascular Resistance / Q000502:physiology