Ocular Ischemic Syndrome Workup

Updated: Jun 10, 2019
  • Author: Tahira M Scholle, MD; Chief Editor: Andrew G Lee, MD  more...
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Workup

Laboratory Studies

Although there are no specific blood tests that are required in the workup of ocular ischemic syndrome (OIS), it is essential to evaluate the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels in patients with suspected giant cell arteritis. [19, 20]

Referral to a primary care physician or cardiologist is recommended to evaluate vascular risk factors. Cholesterol levels and hemoglobin A1c may be evaluated.

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Imaging Studies

Ocular Imaging Studies

Fluorescein angiography

The most sensitive angiographic sign of ocular ischemic syndrome is prolonged retinal arteriovenous time, present in more than 95% of cases; however, this is not specific for ocular ischemic syndrome. Prolonged arm-to-choroid and arm-to-retina time, staining of the retinal vessels (arteries more than veins), leakage from retinal vessels, and retinal capillary nonperfusion may also be seen. [1, 14]

Indocyanine green (ICG) angiography

ICG angiography helps visualize choroidal abnormalities. Arm-to-choroid may be increased, patchy choroidal filling or choroidal filling defects may be seen, or there may be slow filling of the watershed zone (areas between zones supplied by two different vessels). [14]

Ocular coherence tomography (OCT)

In one study, average choroidal thickness was reduced in patients with ocular ischemic syndrome; however, the retinal macular thickness did not differ between patients with ocular ischemic syndrome and age-matched controls. [21] OCT can be also be used to identify macular edema.

Optical coherence tomography angiography (OCT-A)

OCT-A has shown increased foveal avascular zone (FAZ) and decreased retinal vessel density in a case of ocular ischemic syndrome that improved after carotid artery stenting. [22]

Carotid Imaging Studies

Carotid duplex ultrasonography

This is the most commonly used test to diagnose carotid disease. It is a noninvasive method that shows both anatomical imaging of the vessel and flow velocity information. [23, 24, 25]

Magnetic resonance angiography (MRA) and computed tomographic angiography (CTA)

MRA and CTA are second-line noninvasive methods for the evaluation of arterial vessels. These studies can provide accurate anatomical details about intracranial vessels and are often helpful if carotid ultrasonography is not diagnostic or to aid surgical planning.

Carotid angiography

Carotid angiography is an invasive procedure with a 1.2% risk of cerebral infarction. It is typically used only if ultrasonography, MRA, or CTA shows inconclusive or contradictory results. [1, 10]

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Other Tests

Electroretinography

Electroretinography (ERG) can help distinguish ocular ischemic syndrome from central retinal vein occlusion (CRVO) or central retinal artery occlusion (CRAO). In ocular ischemic syndrome, both the inner and outer retina are ischemic. Therefore, ERG in ocular ischemic syndrome shows a reduction in both a-waves (which correspond to photoreceptors) and b-waves (which correspond to bipolar and Muller cells). Eyes with CRVO or CRAO typically have an electronegative ERG result because the inner retina is ischemic but the outer retina is unaffected. [10]

Ophthalmodynamometry and Ocular Plethysmography

Both of these tests can indirectly measure carotid disease by evaluating ophthalmic artery pressure and ocular pulsations. These methods have been replaced by carotid imaging studies.

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