Article

CLINICAL: RETINA

IDENTIFY BLOCKAGE

Ocular ischemic syndrome indicates carotid artery disease

Ocular ischemic syndrome (OIS) is a potentially blinding disorder that may be the first sign of life-threatening carotid artery disease. This can lead to devastating complications, such as a myocardial infarct or stroke.

Cerebral OIS is easily misdiagnosed for other ocular vascular diseases, such as retinal vein occlusions or diabetic retinopathy, because of its similar clinical appearance. In addition, it’s underdiagnosed due to its myriad of ocular complications. (Severe carotid artery stenosis can lead to asymmetric diabetic retinopathy.)

Failure to recognize OIS can result in irreversible blindness, morbidity and mortality (40% within five years of onset, reports Survey of Ophthalmology).

CLINICAL SYMPTOMS

OIS symptoms are diverse:

  • Asymptomatic (with incidental clinical signs)
  • Delayed recovery of vision after exposure to bright light and vice versa, due to macular ischemia
  • Ocular and/or periorbital pain (from neovascular glaucoma or ischemic damage to the branches of the ophthalmic division of the trigeminal nerve)
  • Vision loss (from 20/20 to hand motion)
  • Light after images varying in shape and size (teichopsia)
  • Transient vision loss or amaurosis fugax
  • VF defects (central or centrocecal scotoma, nasal or temporal defects)

Mid-peripheral hemorrhages in an OIS patient.
Image courtesy of Dr. Sherrol A. Reynolds

CLINICAL SIGNS

  • Anterior segment complications. Dilated episcleral vessels, corneal edema, uveitis, a mid-dilated poorly reactive pupil, cataract, iris atrophy, elevated IOP, iris neovascularization or neovascular glaucoma.
  • Posterior complications. Venous dilatation with or without tortuosity (the veins in diabetes and vein occlusions will typically be dilated and involved in the anterior segment), mid-peripheral retinal hemorrhages (typically larger, “spotchy,” compared to diabetes and vein occlusions) and microaneurysms, cotton wool spots, possible cherry red spot (due to retinal hypoperfusion, not embolization), retinal capillary non-perfusion, macular edema and neovascularization of the disc and retina.

DIAGNOSTIC DEVICES

  • FA/IGCA. This helps to eval- uate the retinal and choroidal vascular abnormalities in OIS eyes. Specifically, it aids in detecting delayed and patchy choroidal filling, retinal capillary non-perfusion, late leakage from arterioles and veins, leakage from new vessels and macular edema.
  • SD-OCTA. This aids in detecting abnormal vascular changes from neovascular complexes, subclinical microaneurysms, areas of retinal capillary non-perfusion and impaired retinal and choroidal blood flow.
  • SD-OCT (EDI). This provides high-resolution imaging of OIS, so the O.D. can quantify and monitor edema and detect neovascularization, and the EDI component helps identify changes in the choroid.
  • Ultra-wide field imaging. Wide-angle imaging of the mid-peripheral retina helps the O.D. detect mid-peripheral hemorrhages or microaneurysms.

MANAGEMENT PROTOCOL

A quick screen for carotid artery stenosis includes carotid auscultation to listen for bruits. Bruit absence does not rule out underlying stenosis, though. Thus, all patients suspected of OIS should be urgently referred for primary care, cardiovascular and neurological assessment where lab tests to rule out diabetes, hyperlipidemia and an erythrocyte sedimentation rate (ESR) for giant cell arteritis can be performed.

Therapy for OIS secondary to carotid artery stenosis includes identification and reduction of risk factors, including compliance to medications for systemic diseases (i.e. hypertension, atherosclerosis, and diabetes mellitus), cessation of smoking, physical activity, aspirin, or antiplatelet drug. Carotid endarterectomy surgery is recommended for severe carotid stenosis, specifically those between 60% to 99% blocked, to restore carotid artery patency, reports Medical Science Monitor Journal.

Patients with posterior segment or iris neovascularization should be referred to a retinal specialist for anti-VEGF treatment. Pan-retinal laser photocoagulation, historically used to treat OIS, is effective in 39% of cases, according to Medical Science Monitor Journal. Topical glaucoma and steroid agents may be used to lower IOP and control inflammation in patients who have early neovascular glaucoma, while those with advanced disease may require filtering or shunt surgery, or ciliary body destruction. In cases of anterior uveitis, topical steroidal and non-steroidal drugs and mydriatic agents to prevent posterior synechiae can be used.

UNBLOCK THE ARTERY

OIS is a rare, but significant, vision-threatening disorder associated with life-threatening carotid artery disease. Awareness of the clinical symptoms and signs that differentiate it from the conditions above, along with advances in diagnostic modalities, make the role of the eye care practitioner increasingly important in the early detection of OIS. Failure to do so, can result in serious consequences. OM

Special thanks to Julie Torbit, O.D., F.A.A.O., for reviewing this article.