Microsurgical Anatomy of the Central Retinal Artery

OBJECTIVE: To define the microsurgical anatomy of the central retinal artery (CRA) and to provide a guide to avoiding damage to it during surgery. METHODS: The anatomic characteristics of the CRA and small arteries distributed to the optic sheath were examined in 109 orbits. The origin, course, and site of entry of the artery into the optic sheath and the distance between the orbital apex and the site of entry into the sheath were examined. RESULTS: The CRAs originated directly from the intraorbital ophthalmic artery or in a common trunk with a posterior ciliary or a muscular branch. The CRAs most commonly originated on the inferomedial side of the ophthalmic artery an average of 8.4 mm distal to the orbital end of the optic canal. They penetrated the optic sheath near the junction of the middle and anterior thirds of the length of the intraorbital optic nerve an average of 18.6 mm distal to the optic canal. More than 70% of CRAs penetrated near the midline of the lower surface of the optic sheath, 21% entered the inferomedial surface, and 7% the inferolateral or lateral surface of the optic sheath. Only one CRA gave off a branch before penetrating the nerve. CONCLUSION: The CRA is at risk of being damaged or occluded during procedures involving a large part of the orbit. Procedures directed along the lower half of the proximal two-thirds of the optic sheath have the greatest risk of interrupting the artery.