Dolichoectatic arterial compression of the chiasm and optic nerve: a case report.

Dolichoectatic arterial compression of the anterior visual pathway is a rare but recognized condition. The functional impact, however, is still less clear. We describe a case of a 56-year-old male with diminished visual acuity in the left eye and incongruent inferior visual defect in both eyes caused by dolichoectasia due to a congenital hypoplasia of one horizontal segment of the circle of Willis and subsequent arterial compression of the chiasm and left optic nerve.