The retinopial vein: a vein passing directly from the retina to the pia mater at the optic nerve head.

BACKGROUND/AIMS All blood drainage from the retina is thought to occur through the central retinal vein with rare, if any, exceptions. A chance observation of a specimen in which this pattern did not apply suggested that the subject required review. METHODS An optic nerve head, identified from an earlier study as possessing an unconventional venous drainage arrangement, was examined histologically using interrupted serial resin sections. 200 fundus photographs were examined to compare with the results from the sectioned optic nerve head. RESULTS A retinopial vein passing from the temporal retina and entering the pia mater without first joining the central retinal vein was observed. Two of the fundus photographs and possibly four others displayed a venous pattern consistent with this arrangement. CONCLUSIONS The retinopial vein complements the central retinal vein in blood drainage from the retina. Uncertainty in identifying the vein ophthalmoscopically prevents a reliable estimate of its incidence but it appears to be uncommon. Retinal dysfunction may be limited in cases of central retinal vein occlusion in the presence of a retinopial vein.