| Ocular Ischemic Syndrome Signs and Symptoms
The patient with ocular ischemic syndrome (OIS) is elderly, ranging in age
from the 50s to 80s. Males are affected twice as commonly as females. The patient is only
rarely asymptomatic. Decreased vision occurs at presentation in 90 percent of cases, and
40 percent of patients have attendant eye pain. There may also be an attendant or
antecedent history of transient ischemic attacks or amaurosis fugax. Patients also have
significant known or unknown systemic disease at the time of presentation. The most
commonly encountered systemic diseases are hypertension, diabetes, ischemic heart disease,
stroke, and peripheral vascular disease. To a lesser extent, patients manifest OIS as a
result of giant cell arteritis (GCA).
Unilateral findings are present in 80 percent of cases. Common findings
may include advanced unilateral cataract, anterior segment inflammation, asymptomatic
anterior chamber reaction, macular edema, dilated but non-tortuous retinal veins,
mid-peripheral dot and blot hemorrhages, cotton wool spots, exudates, and
neovascularization of the disc and retina. There may also be spontaneous arterial
pulsation, elevated intraocular pressure, and neovascularization of the iris and angle
with neovascular glaucoma (NVG). While the patient may exhibit anterior segment
neovascularization, ocular hypotony may occur due to low arterial perfusion to the ciliary
body. Occasionally, there is visible retinal emboli (Hollenhorst plaques).
Pathophysiology
The findings in OIS are caused by internal carotid artery atheromatous
ulceration and stenosis at the bifurcation of the common carotid artery. Five percent of
patients with internal artery stenosis develop OIS. However, OIS only occurs if the degree
of stenosis exceeds 90 percent. Stenosis of the carotid artery reduces perfusion pressure
to the eye, resulting in the above mentioned ischemic phenomena. Once stenosis reaches 90
percent, the perfusion pressure in the central retinal artery (CRA) drops only to 50
percent. Often, the reduced arterial pressure manifests as spontaneous pulsation of the
CRA. The findings are variable and may include any or all of the above findings. Ninety
percent of patients with OIS who develop neovascularization of the anterior segment
manifest best corrected vision of finger counting within one year of diagnosis.
Management
Ocular ischemic syndrome is best managed by addressing the causative
factor, namely the carotid artery obstruction as well as the more serious ocular sequelae.
In cases of retinal and anterior segment neovascularization, you must employ pan-retinal
photocoagulation (PRP). PRP causes regression of anterior segment neovascularization in 36
percent of cases. As more of the angle becomes closed by the neovascularization, the
success rate of PRP declines.
Carotid endarterectomy is frequently employed to surgically remove the
carotid obstruction if the carotid artery is less than 99 percent obstructed. Following
surgery, one-third of these cases improve, one-third remain stable, and one-third worsen.
Patients with OIS have significant systemic disease that must be
assessed. Cardiac death is the primary cause of mortality in patients with OIS—the
five-year mortality rate is 40 percent. For this reason, refer patients with OIS to a
cardiologist for complete serology, EKG, ECG, and carotid evaluation.
As OIS may be caused by GCA, patients older than 60 years must
immediately be evaluated with an erythrocyte sedimentation rate (ESR). Should the ESR be
elevated, refer the patient to a neurologist experienced in the management of GCA.
Clinical Pearls
Idiopathic anterior uveitis is relatively rare in elderly
patients. Suspect OIS in elderly patients presenting with an asymptomatic anterior
uveitis.
OIS is a disease typified by asymmetry. Suspect OIS when
patients present with asymmetric retinopathy, asymmetric cataracts, or a unilateral red
eye.
Always consider OIS in elderly patients with
neovascularization of the anterior segment.
Consider OIS when encountering ocular hypotony,
especially if there is concurrent anterior chamber reaction and/or neovascularization.
The retinal veins in OIS will be dilated, but not
tortuous. Tortuosity is a sign of retinal vein occlusion.
Always consider GCA as a cause of OIS and immediately
evaluate the elderly patient with an ESR.
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