The Ocular Ischemic Syndrome

G.C. Brown, M.D., M.B.A. ( )

Jefferson Medical College, Wills Eye Hospital, Philadelphia, PA 19107, USA

e-mail: gary0514@aol.com

M.M. Brown, M.D., M.N., M.B.A.

Research Department, Wills Eye Institute, Jefferson Medical College, Philadelphia, PA, USA

CEO, Center for Value-Based Medicine®, Flourtown, PA, USA

e-mail: mbrown@valuebasedmedicine.com

S. Sharma, M.D., M.Sc. (epid.), M.B.A. Queens Medical College, Kingston, ON, Canada e-mail: sanjay.sharma60@hotmail.com

Introduction

In 1963, Kearns and Hollenhorst [1] described the ocular symptoms and signs associated with severe carotid artery obstructive disease (Table 24.1). They called the entity “venous stasis retinopathy” and noted a prevalence of approximately 5% in their patients with carotid artery obstruction. Misunderstanding has since arisen with the term “venous stasis retinopathy” because the name has also been used to denote a mild central retinal vein obstruction [2]—an

Table 24.1 Symptoms and signs associated with the ocular ischemic syndrome [5, 6, 32]

outflow condition versus the inflow problem seen with carotid artery obstruction. Alternative names proposed include ischemic coagulopathy [3] and ischemic ocular inflammation [4, 5]. Nonetheless, in the majority of cases, clinical and histopathologic examinations of eyes with ocular ischemic disease due to carotid artery obstruction generally fail to demonstrate inflammation [5–8]. The descriptive term proposed by Magargal and Brown [5, 6] is the ocular ischemic syndrome (OIS) [5, 6], an entity not to be confused with mild central retinal vein obstruction and other posterior segment vasculopathies.

Demography

The mean age of patients with the OIS is approximately 65 years, with a range from the 50s to the 80s [5]. No racial predilection has been shown, but males outnumber females by a ratio of 2:1. In approximately 20% of patients, the OIS is bilateral [5].

Sturrock and Mueller [9] reported the annual incidence of the OIS in the UK to be 7.5 cases/ million persons. Extrapolation of these data to the USA suggests an annual incidence of 2,200 cases. Nonetheless, the incidence may be falsely low since it is possible that some cases are misdiagnosed.

Etiology

Typically, a stenosis of 90% or greater in the ipsilateral common carotid and/or internal carotid arterial system is necessary to cause the OIS (Fig. 24.1), while a 50% stenosis is not [5]. It has been shown that a 90% carotid stenosis reduces the central retinal artery perfusion pressure by about 50% [10, 11]. In approximately 50% of cases, the affected carotid vessel is 100% occluded [5].

Obstruction as distally as the ipsilateral ophthalmic artery can also cause the OIS [5, 12, 13]. Rarely, an isolated obstruction of the central retinal artery alone can mimic the dilated retinal veins and retinal hemorrhages seen in eyes with the ocular ischemic syndrome [14]. In this instance, the choroid appears to be unaffected on fluorescein angiography.

Atherosclerosis within the carotid artery is the cause of the majority of OIS cases (Fig. 24.2) [5]. Dissecting aneurysm of the carotid artery has been reported as a cause [15], as has giant cell arteritis [16]. Hypothetically, entities such as fibromuscular dysplasia [17], Behçet’s disease [18], trauma [19], and inflammatory conditions that cause carotid artery obstruction could lead to the OIS.