21.1 Features
Ocular ischemic syndrome (OIS) is a rare but serious disease. While our understanding of this entity has improved, OIS is still often misdiagnosed or missed on initial clinical exam. OIS is an ischemic state caused by a reduction of blood flow to the eye. It is frequently associated with ipsilateral carotid stenosis, yet not all patients with OIS have stenotic carotids. It is important to consider evaluation for other vascular stenosis/occlusions, including within the aortic arch, the ophthalmic artery, central retinal artery, or ciliary arteries, as patients with OIS have a 40% mortality rate at 5 years, often from ischemic cardiac disease.
OIS is more prevalent in individuals over the age of 50 and the incidence rises with increasing age. The rates of OIS in men are twice than those in women. OIS is more common in patients with diabetes, which can confound the diagnosis if there is underlying diabetic retinopathy. Thus recognition of asymmetric diabetic retinopathy should prompt an evaluation for OIS. While typically unilateral, rates of OIS in the fellow eye have been reported to be anywhere between 20 and 50%.
21.1.1 Common Symptoms
May present with a history of transient visual loss (~ 15%) or complain of a dull ache (~ 40%). The etiology of the discomfort may be related to ischemia of the ciliary body (manifested as flare in the eye from breakdown of the blood–aqueous barrier) or frank pain, which may be secondary to neovascularization of the iris (NVI) and secondary neovascular glaucoma (NVG). Patients may also report worsening of the pain when upright, as the reduced blood flow in that position can result in increased ischemia.
21.1.2 Exam Findings
In the anterior segment NVI is frequently present (▶ Fig. 21.1), and many will go on to develop NVG. Patients may also manifest flare in excess of cell in the anterior chamber or a fixed, sluggishly reactive pupil. Rarely, patients may present with bullous keratopathy and Descemet’s folds.
Fig. 21.1 Fluorescein angiography demonstrating neovascularization of the iris in a patient with ocular ischemic syndrome. There is early leakage of the iris vessels visible, even in a dilated eye.
In the posterior segment, classic findings include narrowed arteries and dilated, but not tortuous veins, which can help differentiate OIS from a central retinal vein occlusion (where the veins are generally both dilated and tortuous). Midperipheral hemorrhages are frequently present (~ 80%) and usually deep (dot/blot, ▶ Fig. 21.2). The presence of posterior segment neovascularization, both at the disc and elsewhere, may be seen in severe cases. Occasionally, severe OIS may manifest with a central retinal artery occlusion. This can be associated with NVG, as an increased intraocular pressure can overwhelm the low perfusion pressure of the central retinal artery.
Fig. 21.2 Scattered dot–blot hemorrhages in the midperiphery of a patient who had 99% stenosis of the carotid artery. There is narrowing of the arteries and dilation of the veins, with minimal tortuosity.
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