Visualization of the ophthalmic artery by phase-contrast magnetic resonance angiography: a pilot study

This study aimed at investigating whether phase-contrast (PC) magnetic resonance (MR) angiography is useful for visualizing the ophthalmic artery (OA). This prospective study enrolled 196 consecutive outpatients who underwent three-dimensional PC MR angiography. The basal image parallel to the anteroposterior dimension of the OA was extracted for analysis from the imaging data. The 99 male and 97 female subjects were aged from 10 years to 80 years (mean 47.9 years). The OAs were supplied only by the external carotid system or in combination with the internal carotid artery (ICA) in 18 subjects (9.2 %). The bilateral OAs were symmetrical in 12 %, asymmetrical in 87 %, and unidentified in 1 %. The contour of the proximal segment of the OAs could be classified into straight, curved, and tortuous types. The ICA-OA angle defined by the angle between the approximate line of the proximal OA and the vertical line was also variable. The first bend of the OA corresponded to the anastomosis site with the external carotid system. The proximal medial bend was the origin of the posterior ethmoidal artery, and the distal medial bend was the origin of the anterior ethmoidal artery. According to the results the OA not only possesses three characteristic bends, but also shows prominent individual variability and commonly shows bilateral asymmetry. The contour of the OA may be regulated by the anchor effect at the bend sites. PC MR Angiography is useful for visualizing the main trunk of the OA.