Retinal arteriovenous anastomosis: a case report

ctinal arteriovenous anastoR mosis is a rare type of vascular malformation which may be a neovascular response to venous obstruction in hypertension, may occur after choroiditis or after trauma, but is usually congenital.’ In the congenital form the affected artcry and vein can appear grossly dilated with the interconnections taking on one or more of three manifestations: i. Direct feeding of the end of the artery into the end of the vein without an intervening capillary bed. ii.The artery may supply an angioma which is an oval mass of small vessels usually drained by several small veins. iii.The artery and vein may be connected by an anomalous vessel then continue their course to the retinal periphery. The condition has been reported both bilaterally and unilaterally. In severe cases the disc and macula may be covered with a mass of twisting and tortuous vessels, resembling a can of worms. Sometimes the condition affects only a few vessels. Interestingly visual acuity does not always rcflect the amount of vascular involvement: in the case reported by Cameron’,3 where only a few retinal vessels were affected, the patient had no light perception, probably due to vascular infiltration and destruction of the optic nerve. Although the retinal vascular anomaly is seen in isolation, it is more frequently reported in association with vascular malformations elsewhere. In the most important of these associations, the Wyburn-Mason syndrome, cutaneous, retinal and intracranial vascular malformations centered on the midbrain may be accompanied by: headache, ptosis, ocular paresis, facial palsy, homonomous hemianopia, speech defects, hemiparesis, as well as a risk of sub-arachnoid haemorrhage and hydr~cephaly.~