![]() ![]() Also if the OIS is bilateral or there are associated systemic vascular diseases, this tends to worsen the prognosis.Ĭhris Steele BSc (Hons) FCOptom DCLP DipOC FBCLA. 168 Degree of internal carotid artery stenosis, presence of collateral vessels, and compensation by collaterals are important in assessing OIS disease severity. Insufficient collateral vascular flow in OIS patients explains the frequent association with cerebral infarctions and the poor neurologic outcomes. 167 OIS develops especially in patients with poor collateral circulation between the internal and external carotid arterial systems. Up to 29% of patients with a symptomatic carotid artery occlusion manifest retinal vascular changes that are usually asymptomatic however, 1.5% of them progress per year to symptomatic OIS. Kearns 166 reported that, of patients with occlusion of the internal carotid artery undergoing surgical anastomosis between the superficial temporal artery and the middle cerebral artery, 18% presented with OIS. 163,164 Sturrock and Mueller estimated 7.5 cases per million persons every year, 165 but this is likely an underestimation as OIS can be easily misdiagnosed. Bilateral involvement may occur in up to 22% of cases. Men are affected twice as often as women, 162 reflecting their higher incidence of atherosclerotic disease however, no racial predilection exists. OIS occurs at a mean age of 65 years and is rare before the age of 50. Lutty, in Retina (Fifth Edition), 2013 Ocular ischemic syndrome (OIS) The differential diagnosis of OIS includes central retinal artery occlusion, central retinal vein occlusion, giant cell arteritis, and hyperviscosity syndromes such as leukemia. The 5-year mortality of patients with OIS has been estimated to be 40%, with the majority of deaths occurring as a consequence of cardiovascular disease. The systemic associations found in OIS include diabetes mellitus (56%), hypertension (50% to 73%), ischemic heart disease (38% to 48%), and cerebrovascular disease (27% to 31%). ![]() The prevalence has been estimated at 7.5 per 1 million. ![]() Whereas the disease is usually unilateral in presentation, there is no associated right-left laterality. There is an approximate twofold predilection for males, with no known racial bias. The average age of a patient with OIS is approximately 65 years. A pathognomonic finding of OIS is detection of retrograde blood flow in the ophthalmic artery. Either anastomotic pathway leads to the ophthalmic artery. The anastomotic pathway may be via the angular artery or, alternatively, via the recurrent meningeal artery to the lacrimal artery. In the event of an imperforate anterior communicating artery, or other compromise to the communications of the circle of Willis, the blood flow to the ischemic eye may come from alternative anastomoses from the ipsilateral external carotid artery. Anastomotic perfusion of the affected orbit can come from the circle of Willis via retrograde flow inferiorly in the patent superior portion of the internal carotid artery to the ipsilateral ophthalmic artery. With significant stenosis of the internal carotid artery-usually at the level of the carotid bifurcation-the supply of blood to the ipsilateral eye becomes compromised. The major source of blood flow to the eye and orbital structures is the ophthalmic artery, which is the first major intracranial branch of the internal carotid artery. Not all patients with significant carotid artery occlusion have OIS. Other causes of impaired ocular blood flow and consequent OIS include vasculitides, such as giant cell arteritis, Takayasu's arteritis, or carotid artery dissection. Anterior and posterior segments may be affected with differing degrees of severity. Although the majority of patients with OIS have severe occlusive carotid artery disease, a significant minority do not, with the ocular ischemic condition resulting from occlusive disease of the ophthalmic, central retinal, or ciliary arteries. The reduction of normal blood flow to the eye may result in a variety of signs and symptoms depending on the severity of the compromise, as well as the degree to which anastomotic sources of perfusion are present. Ocular ischemic syndrome (OIS) results from significantly reduced blood flow to the eye and orbit, most often as a consequence of ipsilateral internal carotid artery atherosclerotic stenosis or obstruction. IP MD, in Retinal Imaging, 2006 27.1 Introduction ![]()
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