A 49-year old man was referred to us with painless sudden visual loss in his right eye. Eight days prior to his visit, he received chiropractic manipulation on his neck in a prone position for approximately 10 minutes to improve neck and shoulder stiffness. Immediately after rising, he was unable to see with his right eye. When he first visited our clinic, the best corrected visual acuity in the right eye was hand motion, while the left eye was at 20 / 20. Anterior segment examination was unremarkable, and the right eye had a relative afferent pupillary defect. There was cherry-red spot in the macula in his right eye (Fig. 1), and the arterio-venous transit time in the fluorescein angiogram was delayed (Fig. 2). A cervical color Doppler showed stenosis of the right internal carotid artery (Fig. 3) with diffuse atherosclerotic plaques in the right common carotid artery (Fig. 4). The right anterior communication artery was not visible by magnetic resonance angiogram (Fig. 5).

The patient had been taken hospitalization twice previously because of cerebral infarction. He has suffered from dysarthria, which is sequela of cerebral infarction. He has taken medicine for hypertension and diabetes mellitus for 5 years.

In our case of central retinal artery occlusion, the usual emergency efforts to restore retinal circulation such as ocular digital massage and anterior chamber paracentesis were not performed because eight days had already passed. We prescribed ginko biloba extract (Tanamin; Yuyu Pharmacy, Seoul, Korea), 3 tablets per day. Three years after the patient's first visit, the best corrected visual acuity of his right eye was 20 / 200.

Chiropractic, a discipline founded by D. D. Palmer in 1895, attributes illness to incorrect alignment of spine and seeks to treat diseases by manual manipulation of the spinal vertebrae [1]. Approximately 10% of Americans consult chiropractors an average of seven to ten times per year, accounting for roughly 0.25 billion patients visit per year [1,5]. Despite the large number of treatment sessions, complications following chiropractic treatment have been largely ignored. Askey [6] reported six instances of hemiplegia immediately after spinal chiropractic massage, and Calverley and Millikan [7] and Millikan [8] described a total of seven patients who experienced contralateral paralysis after manipulation of the neck. Jumper and Horton [1] reported a case of central retinal arterial occlusion followed manipulation of the neck by a chiropractor.

Central retinal arterial occlusion (CRAO) often results in profound, permanent loss of vision and is frequently associated with systemic vascular disease [9]. The causes of CRAO include embolism, thrombosis, vasculitis, arterial spasm, arterial dissection, and hypertensive arteriolar necrosis [3]. Of these, embolism is by far the most common cause, and the major source of emboli is a plaque in the carotid artery [10]. The risk factors for arterial occlusive disease include hypertension, coronary artery disease, diabetes mellitus, hypercholesterolemia, and tobacco use [9-11].

Here, we reported on a patient with central retinal artery occlusion following chiropractic neck manipulation. We suspect that cervical manipulation by the chiropractor dislodged an embolus from an artherosclerotic plaque in the right common carotid artery, which was obstructing the right internal carotid artery.

In conclusion, before undertaking neck manipulation, chiropractors and other medical personnel should inquire about a history cervical vascular disease, especially in older patients. The carotid artery should always be handled gingerly in patients with known or suspected artherosclerotic disease.