The ocular ischaemic syndrome illustrates well the effects of hypoperf
usion of the globe and is a useful model for studying disorders of the
orbital circulation. Recent advances in orbital ultrasound techniques
have provided a non-invasive method of examining flow velocities in t
he orbital vessels, particularly the ophthalmic artery. Orbital ultras
ound studies were performed on 3 cases of the ocular ischaemic syndrom
e. Continuous or intermittent reversal of blood flow in the ophthalmic
artery was seen in all cases. How this phenomenon relates to the symp
toms and signs in affected patients, and the role of orbital ultrasoun
d in the investigation of the ocular ischaemic syndrome, are discussed
.